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Recovery behavior of high ammonium inhibition in a sequencing batch biofilm reactor
Journal Pre-proof Recovery behavior of high ammonium inhibition in a sequencing batch biofilm reactor
Qian Wang, Chunfang Chao, Yingxin Zhao PII:
S2589-014X(19)30205-1
DOI:
https://doi.org/10.1016/j.biteb.2019.100315
Reference:
BITEB 100315
To appear in:
Bioresource Technology Reports
Received date:
31 March 2019
Revised date:
31 August 2019
Accepted date:
2 September 2019
Please cite this article as: Q. Wang, C. Chao and Y. Zhao, Recovery behavior of high ammonium inhibition in a sequencing batch biofilm reactor, Bioresource Technology Reports(2019), https://doi.org/10.1016/j.biteb.2019.100315
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© 2019 Published by Elsevier.
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Recovery behavior of high ammomium inhibition in a sequencing batch biofilm reactor Qian WANG a†, Chunfang CHAO a†, Yingxin ZHAO a,* a School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China †
Q. Wang and C. Chao contributed equally to this article.
*Corresponding author: Yingxin Zhao; School of Environmental Science and Engineering, Tianjin
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University, Tianjin 300072, China. E-mail: [email protected] (Y.Zhao). Tel/Fax: +86 22 2740 6057
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Abstract: Few studies have investigated the process of microbial recovery from wastewater
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inhibited by high-strength ammonium but focused on the inhibition effects only. In this study, one contrast way and four efficient ways were developed and applied to five parallel sequencing batch
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biofilm reactors (SBBRs). The effluent ammonia nitrogen (NH4+-N), nitrite nitrogen (NO2--N),
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nitrate nitrogen (NO3--N), total nitrogen (TN), chemical oxygen demand (COD) and total phosphorus (TP) concentrations were investigated to assess the recovery effects of removal rates as
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well as the recovery mechanism. Results showed that all of these methods have a positive effect, among which introducing algae was optimum for the fast removal recovery of TN and TP within 4 days. And its recovery time is at least 8 days shorter than that in natural recovery. The recovery ways proposed in this study can be potentially applied in the emergency treatment in SBBR system. Key words: Ammonium inhibition, Fast recovery, Rural wastewater, Sequencing batch biofilm reactors
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1. Introduction Rural wastewater treatment has received worldwide attention (Massoud et al., 2009). A large number of untreated rural sewage discharges are disorderly, seriously polluting soil, surface water and groundwater, which affects the safety of drinking water and poses a great threat to rural
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ecological environment. The current comprehensive treatment rate of rural sewage is very low, for example, it is only about 20% in China. Therefore, developing an effective approach to reduce rural water pollution is important and imminent (Wan et al., 2009; Li et al., 2012; Gu et al., 2016).
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Sequencing batch biofilm reactor (SBBR), a combination of traditional activated sludge process
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and biofilm process, is suitable for intermittent discharge of rural sewage and large change of pollutant loading. In our previous study, periodical results have achieved by using SBBR to treat
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rural wastewater in salinized areas (Zhao et al., 2017). A fast start-up with high biofilm attachment
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of 7275.0 mg/L and high removal efficiency of pollutants were demonstrated. From the aspect of
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stable operation, impact loading including heavy metal impact (Wang et al., 2015; Wang et al., 2016), high-strength ammonia shock (Wei et al., 2017) will negatively affect the efficient removal of nitrogen, phosphorus and organic matters. A long-term survey has done to evaluate the characteristics of rural sewage, and it was found that non-point source pollution in storm, high ammonium accumulation in winter, and substandard discharge of industrial wastewater could possibly lead to ammoium inhibition of SBBR system in rural area (Quan and Yan, 2002). Hockenbury and Grady (1997) reported that industrial wastewater containing high ammonia nitrogen entering rural sewage treatment plants inevitably inhibited biological activities, resulting in
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a decline in the performance of biological wastewater treatment systems. High-intensity ammonium nitrogen has a large effect on the removal ratio of nitrogen and phosphorus through biological mechanisms (Mahendraker et al., 2010). Wang et al (2009) found that when the influent chemical oxygen demand/total phosphorus (COD/TP) and chemical oxygen demand/total nitrogen (COD/TN) ratios were 19.9 and 9.9, and the optimum phosphorus and
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nitrogen removal rates could be achieved at 94% and 91%, respectively. In the case of lower COD/TN (3.5), the removal efficiency of nitrogen and phosphorus were significantly reduced. If the ammonium concentration was too high, the nitrifying bacteria would lose their activity (Wu et al.,
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2008; Li and Zhao, 2006), and it took a long time for natural recovery after inhibition.
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Since the hydraulic retention time (HRT) of SBBR can change the aerobic anaerobic time of the
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system, the living environment of microorganisms and its metabolism time are affected
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correspondingly. Muhamad et al. (2012) confirmed that improving HRT is beneficial to the pollutant removal efficiency of SBBR system. In addition, studies have shown that the addition of other
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substances in the system can also improve the removal efficiency of SBBR for TN, TP and COD by affecting the microbial community structure and reproductive characteristics, such as Granular Activated Carbon (GAC) (Osman et al., 2013), Microalgae (Li et al., 2012) and Bioaccelerators (Wang
et
al.,
2015;
Wang
cytokinins and L-aspartate were effective
et
al.,
2016).
It was
ingredients of bioaccelerators.
reported Biotin
that has
biotin, a
good
promoting effect on the growth of microorganisms in activated sludge (Lawson et al., 2000; Oda et al., 2000). Among the cytokinins, 6-benzylaminopurine is widely used, and plays an important role in cell growth, differentiation and other related physiological activities (Singh P, Mohanta T K,
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Sinha A K., 2015). Cokesa et al. (2004) found that L-aspartate can release ammonia during the deamination process, and this metabolite ammonia may be induced by ammonia lyase. Therefore, biotin, cytokinin and L-aspartic acid, were selected as bio-accelerators for further study. Most previous studies have focused on the inhibition effects of high-strength ammonium, while they mainly paid attention to the inhibition and few studies tried to develop effective mothods
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during recovery period to promote bioactivity recovery. This study aims to develop effective recovery ways (natural recovery, extending hydraulic retention time, adding granule activated carbon (GAC), adding bio-accelerator, introducing algae) to relieve high ammonium inhibition of
2. Materials and Methods 2.1. The bioreactor and inoculation
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SBBR system and compare their recovery effects. The recovery mechanism will also be discussed.
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These five SBBRs were inoculated with the activated sludge from a secondary settling tank
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(Jingu wastewater plant, Tianjin, China). In the inoculated sludge, the content of mixed liquor suspended solids (MLSS) was 8220.0 mg/L, and the mixed liquor volatile suspended solids
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(MLVSS) was 5245.0 mg/L. So the rate of MLVSS and MLSS was 0.63, while the sludge volume index (SVI) in inoculated sludge was 64.48 mL/g. The seed sludge were cultivated in five identical SBBRs with 4.25 L working volumes, namely SBBR-1 (natural recovery), SBBR-2 (extending hydraulic retention time for recovery), SBBR-3 (adding GAC for recovery), SBBR-4 (adding bio-accelerator for recovery) and SBBR-5 (introducing algae for recovery). The reactor was made of Plexiglass, and the dimensions of this reactor were 22.0 cm × 15.0 cm × 19.0 cm (diameter × eight × inner diameter). In this study, all of the SBBRs were equipped with a water trap in the center. The water trap has 72 holes, each inserting a spiral fibers (shape like aquatic-grass, 15.0 cm of each). The reactor was covered by a lid with
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Journal Pre-proof holes in it. Microbial growth requires an intermittent anoxic environment, which is manufactured by an air compressor. Each SBBR has two peristaltic pumps for the effluent and influent of the system. The SBBR-1 was set as the control group, and the pollutants removal was recovered by nature. The volume of the added GAC with particle size of 6-8 mm was about 30% of the reactor volumein SBBR-3 to enhance the system performance recovery. For the SBBR-4, the bio-accelerator (0.01
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μg/L biotin, cytokinin and L-aspartic acid) was dosed during the whole recovery phase in the influent synthetic wastewater. The algae (chlorella L166) with the concentration at 1.043 g/L were added into the SBBR-5, the photo period was half-day (12 h light and 12 h dark) and the photo
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intensity was 5000 ± 200 lx in SBBR-5.
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2.2. Experimental operation
The operation of these reactors was divided into three phases, namely culturing phase (1-18
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days), ammonia nitrogen suppressing phase (19-25 days) and recovery phase (26-40 days).
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In the culturing phase, all of the SBBRs were operated in a cycle of 9.0 hours, including four
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phases: influent (0.5 hour), anaerobic (3.0 hours ), aerobic (5.0 hours), effluent (0.5 hours). In influent, there were four kinds of chemicals: NaHCO3 (174.9 mg/L); NH4+-N (42.0 mg/L); COD (420.0 mg/L); TP (6.0 mg/L), and the pH was maintained at 7.0 ± 0.2. There are two stages in the biofilm acclimation process, aerobic and anaerobic. The concentration of dissolved oxygen (DO) was kept at 6.0-7.0 mg/L in the former one and at less than 0.1 mg/L during the latter phase. The temperature of this study was always maintained at 20 ± 1 °C, and the volume used for exchange was 50%. The sign of domestication of inoculated sludge is that the removal efficiency of TP, TN and COD has not changed significantly within 7 days.
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In the ammonium nitrogen suppressing phase, the SBBRs were also operated in the 9.0-h cycle as in the culturing phase and the pollutants concentration in influent were as follows: NaHCO3 (174.9 mg/L); NH4+-N (200.0 mg/L); COD (420.0 mg/L); TP (6.0 mg/L). In the recovery phase, the SBBRs were still operated in the cycle of 9.0 hours as in the culturing phase except the SBBR-2, the SBBR-2 was operated in a cycle of 13.0 hours, including four phases:
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influent (0.5 hour), anaerobic (3.0 hours ), aerobic (9.0 hours), effluent (0.5 hours), as shown in Table 1. The concentration of NaHCO3, NH4+-N, COD and TP in synthetic wastewater prepared with tap water were 174.9 mg/L, 42.0 mg/L, 420.0 mg/L and 6.0 mg/L, respectively. All of the chemical
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reagents used in this study were analytically pure.
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To explain the effect of HRT on the recovery of SBBR system behavior，the variation of COD,
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TN, NH4+-N, nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N) and TP concentration in a total
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operation cycle during the recovery phase were studied, and there were 6 water samples collected from the SBBR-2 every 2.0 h, beginning in anaerobic phase and ending in aerobic phase.
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The adsorption experiment to illustrate the adsorption ratio of COD, TN and TP by the GAC was carried out at 20 ± 1 °C with pH at 7.0 ± 0.2 in a 15 mL sealed plastic tube for 9.0 h. The adsorbent dose was about 15 cm3 and the initial concentration of COD, TN and TP was 420.0 mg/L, 42.0 mg/L and 6.0 mg/L, respectively. 2.3. Analytical methods
The COD was detected by cuvette rapid tests using HACH DR2800 (21259-15, USA). The contents of nitrogen and phosphorus were quantified according to Chinese national standard methods:
TN
(HJ636-2012),
NH4+-N
(HJ535-2009), 6
NO2−-N
(GB7493-87),
NO2−-N
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(HJ/T346-2007), TP (GB11893-89). The MLSS and MLVSS were measured according to the gravimetric method. The temperature and DO were monitored using an online detector (Model 6308DT, China), the pH was detected through a pH meter (Mettler FP20, Switzerland). The concentration of chlorophyll-a was detected according to the specification for oceanographic survey and marine biological survey. The measurements
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mentioned above were performed in parallel three times and the results were averaged. 3. Results and discussion 3.1. Inhibition of high-strength ammonium
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After 5 days of SBBR operation, the COD removal rate in the reactor was nearly 100%. The
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average removal rates of TN and TP in phase I reached 74.16% and 94.12%. Fig. 1 revealed that the
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removal rate of COD and NH4+-N decreased rapidly after the bioreactor is subjected to high-strength
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ammonium afftect. At the end of phase II (25 d) , the removal rate of TN was 34.15%. The percentages of NH4+-N, NO2--N and NO3--N in TN were 76.45%, 8.94% and 13.95%, respectively.
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The obvious decrease of TN removal was attributed to the inhibition of nitrification process. So there was a large amount of NH4+-N stranded and cannot be converted to NO2--N or NO3--N. The similar phenomena was found in Wang’s study, and the high concentration of NH4+-N (200.00 mg/L) inhibited the nitrification reaction with nitrogen removal rate decreased by 40.91% (Wang et al., 2010). On one hand, it interfered with the metabolism of the cells and a relatively long time was taken to show the negative effect. On the other hand, it could destroy the initial oxidizing power of the bacteria in a short time. This deduction was consistent with the findings of Ilies and Mavinic (2001). In addition, ammonia nitrogen was the basic nitrogen source for anaerobic microorganisms,
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but if the concentration is too high, it will have a toxic effect on anaerobic microorganisms, and was not conducive to the formation of biofilm. Ammonium entered the denitrifying bacterial cell by passive diffusion, changing the proton balance of cell. Moreover, the accumulation of intracellular ammonium caused a change in its pH value, which in turn had toxic effects on cells (Yenigün et al., 2013). Therefore, in the biological treatment of sewage, high-strength ammonium conditions
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simultaneously reduced the activity of nitrifying bacteria and denitrifying bacteria. It can be seen from Fig. 1 that after the completion of the phase II, the removal rate of TP was reduced from 97.99% at the phase I to 41.20%. Because the NH4+-N content of the influent water
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was too high, so there was a part of NO3--N residue in the remaining mixture after one cycle of the
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reactor operation. At this time, the COD content in the system was very low, which casused the
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competition between denitrifying bacteria and phosphorus accumulating organisms (PAOs) for
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organic substances. Therefore, only at the end of the denitrification phase, PAOs can release phosphorus when the system completely entered the anaerobic state, which directly affected the
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efficiency of phosphorus release (Xu et al., 2011). Studies have confirmed that under certain conditions, more phosphate release in anaerobic phase could promote the phosphorus absorption by PAOs in aerobic phase. (Chen, 2007), so the high-intensity NH4+-N impact reduced the phosphorus removal ratio of the system or even destroyed it. 3.2. Recovery of the SBBR system 3.2.1. Recovery of the system by nature The natural recovery of the SBBR system was shown in Fig. 1 without changing any operating condition of the reactor. It showed that the removal rate of NH4+-N in the culturing phase was nearly
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the NO3--N concentration gradually returned to the stable value of the culturing phase. As seen in Fig. 1a at the end of the phase II (25 d), there was no significant effect on the COD removal rate of the reactor (Fig. 1a). It can be seen from Fig. 1b that after the concentration of NH4+-N returned to
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the initial concentration (42.00 mg/L), the NH4+-N concentration in the effluent decreased rapidly at
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first and then slowing down. When the reactor was operated for 38 days, the removal rate of NH4+-N was 98.38%, reaching the level before ammonia nitrogen shock. Moreover, in phase III, the
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concentration of NO2--N in the effluent decreased steadily, and NO3--N increased first with the highest value at 31 days and then decreased (Fig. 1c). It indicated that the activity of nitrifying
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bacteria was first restored compared to denitrifying bacteria. The removal rate of TN reached a maximum of 78.64% as phase I at 38 days. For TP, the removal efficiency (94.60%) did not recovered to phase I (98.47%) until the end of phase III, indicating the degree of recovery of PAOs activity was limited in 15 days. 3.2.2. Recovery of the system by extending hydraulic retention time (HRT) As shown in Fig. 2，the concentration of NH4+-N and NO2--N didn't change obviously during the anaerobic phase, while the concentration of NO3--N decreased significantly, indicating effective denitrification at this stage. The degradation of COD was also observed in the anaerobic phase due
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to the fact that denitrifying bacteria were heterotrophic microorganisms. There was a small increase in TP concentration during the anaerobic phase and a significant decrease in the aerobic phase (Fig. 2e), confirming that the biological phosphorus removal process in the SBBR system was a typical PAOs mechanism for phosphorus release and uptake. Win et al. (2016) and Zhang et al. (2016) had confirmed that the performance of micropollutant
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degradation and wastewater treatment can be improved by changing HRT duration in MBR system, because the change of HRT affects the relationship between bacterial community and system efficiency. In this study, after the aerobic time changes from 5 h to 9 h, the recovery effect of the
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SBBR system was significantly improved. Comparing to SBBR-1 the time required for TN and TP
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removal was reduced by 7 days and 9 days. As shown in Fig. 3, at the first day of the phase III (26
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days), the concentration of NH4+-N in the reactor decreased to 10.68 mg/L. NH4+-N and NO3--N
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accounted for 27.63% and 69.26% of TN, respectively. Obviously increasing the aerobic time increased the action time of the nitrifying bacteria, and the nitrogen conversion process in the
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nitrification stage was promoted. At the same time, the increase of aerobic time also provided sufficient time for PAOs to take up phosphate from wastewater, which promoted the phosphorus removal effeciency of the recovery system. 3.2.3. Recovery of the system by adding granular activated carbon (GAC) On the second day of the phase III (day 27 of system operation), the concentration of NO3--N immediately decreased from 50.69 mg/L to 12.73 mg/L (Fig. 4c), accounting for 65.01% of TN, indicating the activity of denitrifying bacteria was rapidly recovered in a short time after the addition of GAC. At day 31, the removal rate of effluent NH4+-N was nearly up to 100% (Fig. 4b), which
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was 7 days shorter than that in SBBR-1. It revealed that the activity of nitrifying bacteria was also significantly improved. At day 31 and 37 of the reactor operation, the removal rates of TN and TP were substantially restored to the levels as phase I. Due to the high specific surface area and porosity, GAC
had
strong
adsorption
capacity.
A verification
experiment was conducted to
demonstrate the adsorption ability of GAC on COD, TN and TP in wastewater, as shown in Table
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2. Results showed that nearly 30% removal efficiency of COD, TN and TP was acheived by GAC adsorption. This partly contributed to the improvement of the recovery process. Moreover, the rough texture of GAC was beneficial to the adhesion of microorganisms, providing an excellent carrier for
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the formation of biofilm. Similar study reported that the growth rate of autotrophic nitrifying
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bacteria in high-strength ammonium wastewater was severely limited, and the growth of particulate
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aerobic sludge was also limited (Tao et al., 2017). Nevertheless, the addition of GAC promoted the
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formation of particulate aerobic sludge (Wei et al., 2013). From Fig. 4e, d, it can be clearly observed that the recovery of the nitrogen removal after GAC introduction was obviously rapid than that of
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phosphorus, probably because a variety of bacteria have a competitive relationship in the process of forming biofilm on the surface of GAC, and PAOs was inferior in competition. 3.2.4. Recovery of the system by adding bio-accelerator After the addition of the bio-accelerator, the concentrations of NH4+-N, NO2--N and NO3--N in the effluent showed a rapid decline at the same time. At 31, 26 and 29 days, their concentrations recovered to the level of phase I (Fig. 5b, c, d), and the recovery time required for NH4+-N removal (96.6%) was 7 days shorter than that in SBBR-1. It was clear that nitrogen removal was significantly improved with the activities of nitrifying bacteria and denitrifying bacteria quickly recovered. The
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removal rates of TN and TP reached 80.06% and 96.6% at 35 and 34 days, respectively, which recovered to the level as phase I (Fig. 5d, e). It can be seen that the addition of bio-accelerator was beneficial to the rapid recovery of microorganisms after inhibition by high-intensity ammonium. After being impacted, ammonium diffuses into the cells and accumulates through passive diffusion, thereby breaking the balance of
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protons. The biopromoter (cytokinin) contains 6-mercaptoaminopurine, which can cause changes in a series of conductive substances in the cell (Inoue et al., 2001). It is conducive to rebuild the internal and external balance of cells and alleviating the poisoning state. The special function of
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growth factors also contributed to the recovery phase. For example, biotin can improve the ability of
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activated sludge flocs (Oda et al., 2000). Cytokinins can promote the growth and reproduction of
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nitrifying bacteria. Miljkovic et al. (2015) found that a substrate containing cytokinins can increase
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the growth rate and fermentation rate of microorganisms. At the end of the reactor run (40 days), the removal efficiency of TP reached 99.67%, slightly
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higher than the pre-impact value of 96.54%. The concentration of NO3--N in SBBR-4 was maintained at 6 mg/L after the phase III (Fig. 6c), which was much lower than 9 mg/L in SBBR-1. Moreover, compared with SBBR-1, the recovery of TN and TP removal rates were advanced by 3 days and 6 days, which may be due to the fact that the addition of bio-accelerators is more effective in improving the activity of PAOs. 3.2.5. Recovery of the system by introducing algae After adding algae to the system, similar to the result of SBBR-1, the concentrations of effluent NH4+-N and NO2--N were continuously reduced in the initial stage of the recovery phase, and
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The removal rates of TN and TP were recovered to 79.93% and 98.04% during the acclimation period as shown in Fig. 6d, e. The time for recovery was reduced by 7 and 10 days compared to natural recovery conditions. At the end of the recovery period, the removal efficiency of TN and TP
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reached 88.28% and 98.97%, both higher than that in phase I. Studies had shown that the removal
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efficiency of total nitrogen and phosphoric acid in algae bacterial particle systems (50.2% and
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35.7%) was better than that of pure aerobic particle systems (32.8% and 25.6%) (Liu et al., 2018).
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The introduction of microalgae to SBBR can promote the recovery of the system while also improve the removal rate of TN and TP. Because this method increased the amount of organisms in
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the wastewater, at the same time, a microalgae-bacterial symbiosis system was formed. The CO2 produced by bacteria provides the raw material for photosynthesis of microalgae, and the O2 produced by light and action in turn promotes the metabolic process of bacteria, which is beneficial to rapid recovery. Tang et al. (2017) demonstrated that algae-assisted SBBR systems could effectively remove TN and TP. 3.3. Comparison of different recovery methods The time required for the five recovery methods to restore the removal efficiency of NH4+-N, TN and TP in the reactor to the level before impacted was listed in Table 3. As shown in Table 3, the
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recovery time used by SBBR-5 was the shortest. Furthermore, when the system stopped as it was running for 40 days, the removal efficiency of TN and TP reached 88.28% and 98.97%, both higher than the removal efficiency during the acclimation period. The microbial community in the sewage interacts with the microalgae, which promotes the biological treatment of the sewage. Hernandeze et al. (2013) treated the high-ammonia nitrogen concentration of pig-raising wastewater by the
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bacterial-algal symbiosis system. The removal efficiencies of nitrogen and phosphorus were 82.7% and 58.0%. Moreover, algae are autotrophic organisms, which can synthesize their own complex organic components using nitrogen and phosphorus. In addition, algae cells have high protein,
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amino acid content and high production rate. They can be reused as animal feed and bait after
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harvesting. Therefore, the bacterial algae system is effective and can be potentially applied in the
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recovery of high-ammonia-inhibiting biological process.
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4. Conclusion
In this study, five ways were developed to promote the recovery efficiency of SBBR which
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were inhibited by high-strength ammonium. Results showed 200.00 mg/L NH4+-N inhibited more than 50.00% removal efficiency of NH4+-N, TN and TP within 2 days. Comparing to natural recovery, extending HRT, adding GAC or bio-accelerator, introducing algae was most effective with recovery time for TN and TP both in 4 days. Moreover, it further improved the removal efficiency of TN and TP to 88.28% and 98.97%, which were both higher than that in the initial acclimation period. Acknowledgements
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This work was supported by the National Key R&D Program of China (Project
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No.SQ2018YFGH000422).
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References Chen, Q., 2007. Factors of influencing biological denitrification and dephosphorization. Pollut. Ctrl. Technol. Cokesa, Z., Knackmuss, H., Rieger, P., 2004. Biodegradation of all stereoisomers of the EDTA substitute iminodisuccinate by Agrobacterium tumefaciens BY6 requires an epimerase and a
pr oo f
stereoselective C-N lyase. Appl. Environ. Microb. 70, 3941-3947. GB7493-87. Water quality-Determination of nitrogen (nitrite) -spectrophotometric method. Ministry of Environmental Protection. China. GB11893-89.
Water
quality-Determination
of
total
phosphorus-Ammonium
molybdate
e-
spectrophotometric method. Ministry of Environmental Protection. China. Gu, B., Fan, L., Ying, Z., Xu, Q., Luo, W., Ge, Y., Scott, S., Chang, J., 2016. Socioeconomic
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constraints on the technological choices in rural sewage treatment. Environ. Sci. Pollut. R. 23, 20360-20367.
al
HJ636-2012. Water quality-Determination of total nitrogen-Alkaline potassium persulfate digestion
HJ535-2009.
Water
ur n
UV spectrophotometric method. Ministry of Environmental Protection. China. quality-Determination
of
ammonia
nitrogen-Nessler’s
reagent
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spectrophotometry. Ministry of Environmental Protection. China. HJ/T346-2007. Water quality-Determination of nitrate-nitrogen-Ultraviolet spectrophotometry. Ministry of Environmental Protection. China. Hernández, D., Riano, B., Coca, M., García-González, M., 2013. Treatment of agro-industrial wastewater using microalgae-bacteria consortium combined with anaerobic digestion of the produced biomass. Bioresour. Technol. 135, 598-603. Hockenbury, M.R., Grady, C.P.L., 1977. Inhibition of nitrification-effects of selected organic compounds. Journal. 49, 768-777. Ilies, P., Mavinic, D.S., 2001. The effect of decreased ambient temperature on the biological nitrification and denitrification of a high ammonia landfill leachate. Water Res. 35, 2065-2072. 16
Journal Pre-proof Inoue, T., Higuchi, M., Hashimoto, Y., Seki, M., Kobayashi, M., Kato, T., Tabata, S., Shinozaki, K., Kakimoto, T., 2001. Identification of CRE1 as a cytokinin receptor from Arabidopsis. Nature. 409, 1060-1063. Lawson, P., Collins, M., Schumann, P., Tindall, B., Hirsch, P., Labrenz, M., 2000. New LL-diaminopimelic acid-containing actinomycetes from hypersaline, heliothermal and meromictic Antarctic Ekho Lake: nocardioides aquaticus spnov and friedmannielly lacustris spnov. Syst. Appl. Microbiol. 23, 219-229.
pr oo f
Li, H., Hao, M., Liu, J., Chen, C., Fan, Z., Wang, X., 2012. Effect of pH on biologic degradation of Microcystis aeruginosa by alga-lysing bacteria in sequencing batch biofilm reactors. Front. Env. Sci. Eng. 6, 224-230.
Li, J., Zhao, Q., 2006. Study of factors influencing ammonia nitrification. J. China Univ. Min.
e-
Techno. 35, 120-124.
Pr
Liu, L., Zeng, Z., Bee, M., Gibson, V., Wei, L., Huang, X., Liu, C., 2018. Characteristics and performance of aerobic algae-bacteria granular consortia in a photo-sequencing batch reactor. J.
al
Hazard. Mater. 349, 135-142.
Li, Z., Zhang, J., Chen H, Zhang, L., Kang, Q., Feng, Y., 2012. Water pollution situation and impacts
ur n
in rural China. Agr. Sci. Tech. 13, 1055-1059. Muhamad, M., Abdullah, S., Mohamad, A., Rahman, R., Kadnum, A., 2012. Effect of hydraulic
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retention time (HRT) on pentachlorophenol (PCP) and COD removal in a pilot GAC-SBBR system for the post-treatment of recycled paper mill wastewater. Desalin. Water Treat. 48, 50-59. Miljkovic,
D.,
Blazevski,
J.,
Petkovic,
F., Djedovic, N., Momcilovic, M.,
Stanisavljevic, S., Jevtic, B., Stojkovic, M.M., Spasojevic, I., 2015. A comparative analysis of multiple sclerosis relevant anti-inflammatory properties of ethyl pyruvate and dimethyl fumarate. J. Immunol. 194, 2493-2503. Mahendraker, V., Mavinic, D.S., Rabinowitz, B., Hall, K.J., 2010. The impact of influent nutrient ratios and biochemical reactions on oxygen transfer in an EBPR process-a theoretical explanation. Biotechnol. Bioeng. 91, 22-42. 17
Journal Pre-proof Massoud, M.A., Tarhini, A., Nasr, J.A., 2009. Decentralized approaches to wastewater treatment and management: Applicability in developing countries. J. Environ. Manage. 90, 652-659. Osman, W., h, S., Mohamad, A., Kadhum, A., Rahman, R., 2013. Simultaneous removal of AOX and COD from real recycled paper wastewater using GAC-SBBR. J. Environ. Manage. 121, 80-86.Abdulla Oda, Y., Slagman, S., Meijer, W., Forney, L., Gottschal, J., 2000. Influence of growth rate and starvation on fluorescent in situ hybridization of rhodopseudomonas palustris. Fems Microbiol. Ecol. 32, 205-213.
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Quan, W., Yan, L., 2002. Effects of agricultural non-point source pollution on eutrophica-tion of water body and its control measure. Acta Ecologica Sinica. 22, 291-299. Singh, P., Mohanta, T., Sinha, A., 2015. Unraveling the intricate nexus of molecular mechanisms governing rice root development: OsMPK3/6 and Auxin-Cytokinin interplay. Plos One. 10,
e-
230-234.
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Tang, C., Zuo, W., Tian, Y., Wang, Z., Zhang, J., He, Z., 2017. Enhanced nitrogen and phosphorus removal from domestic wastewater via algae-assisted sequencing batch biofilm reactor.
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Bioresour. Technol.
Tao, J., Qin, L., Liu, X., L,i B., Chen, J., You, J., Shen, Y., Chen X., 2017. Effect of granular
2017, 236:60-67.
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activated carbon on the aerobic granulation of sludge and its mechanism. Bioresour. Technol.
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Wang, F., Ding, Y., Ge, L., Ren, H., Ding, L., 2010. Effect of high-strength ammonia nitrogen acclimation on sludge activity in sequencing batch reactor. J. Environ. Sci. 22, 1683-1688. Wang, Y., Ji, M., Zhao, Y., Zhai, H., 2016. Recovery of nitrification in cadmium-inhibited activated sludge system by bio-accelerators. Bioresour. Technol. 200, 812. Win, T.T., Kim, H., Cho, K., Song, K.G., Park, J., 2016. Monitoring the microbial community shift throughout the shock changes of hydraulic retention time in an anaerobic moving bed membrane bioreactor. Bioresour. Technol. 202, 125–132. Wan, D., Liu, H., Qu, J., Lei, P., Mao, S., Hou, Y., 2009. Using the combined bioelectrochemical and sulfur autotrophic denitrification system for groundwater denitrification. Bioresour. Technol. 100, 142-148. 18
Journal Pre-proof Wei, D., Xue, X., Chen, S., Zhang, Y., Yan, L., Wei, Q., Du, B., 2013. Enhanced aerobic granulation and nitrogen removal by the addition of zeolite powder in a sequencing batch reactor. Appl.
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Microbiol. Biot. 97(20):9235-9243.
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Figure Captions Fig.1 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2--N and NO3--N, (d) TN, (e) TP in SBBR-1 Fig.2 The variation of (a) COD, (b) TN, (c) NH4+-N, (d) NO3--N, NO2--N, (e) TP concentration in a total operation cycle during the recovery phase in SBBR-2
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Fig.3 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-2
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Fig.4 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-3
Fig.5 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-4
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Fig.6 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-5
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Table Captions Table 1 The cycle time in recovery phase. Table 2 Water quality change before and after adsorption of GAC.
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Table 3 Time required for recovery efficiency in different reactors.
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Fig.1 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2--N and NO3--N, (d) TN, (e) TP in SBBR-1.
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Fig.2 The variation of (a) COD, (b) NH4+-N, (c) NO3--N, NO2--N, (d)TN, (e) TP concentration in a total operation cycle during the recovery phase in SBBR-2.
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Fig.3 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-2.
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Fig.4 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-3.
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Fig.5 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-4.
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Fig.6 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-5.
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Journal Pre-proof Table 1 The cycle time in recovery phase. Influent
Anaerobic
Aerobic
Effluent
9.0-h
0.5 h
3.0 h
5.0 h
0.5 h
13.0-h
0.5 h
3.0 h
9.0 h
0.5 h
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Phase
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Journal Pre-proof Table 2 Water quality change before and after adsorption of GAC. NH4+-N（mg/L ）
TP（mg/L）
pH
Before
458
42.63
6.35
7.64
After
323
28.15
4.44
8.27
Removal efficiency
29.47%
33.97%
30.06%
—
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COD（mg/L）
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Journal Pre-proof Table 3 Time required for recovery in different reactors. SBBR-1
SBBR-2
SBBR-3
SBBR-4
SBBR-5
NH4+-N
38 d
31 d
31 d
31 d
29 d
TN
38 d
31 d
31 d
35 d
31 d
TP
40 d
31 d
37 d
34 d
30 d
SBBR-1 to SBBR-5 represent: natural recovery; extending HRT recovery; adding GAC recovery; adding bio-accelerator recovery; adding algae recovery.
Conflict of interest
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The authors declare that they have no conflict of interest.
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Highlights 1. High ammonium reduced the TN and TP removal efficiency of TN and TP by 50%. 2. Five ways were proposed to recover the ammonium inhibition of SBBR. 3. Introducing algae was optimum for the fast removal recovery of TN and TP. 4. The SBBR system could be recovered in 4 days after introducing algae.
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Qian Wang, Chunfang Chao, Yingxin Zhao PII:
S2589-014X(19)30205-1
DOI:
https://doi.org/10.1016/j.biteb.2019.100315
Reference:
BITEB 100315
To appear in:
Bioresource Technology Reports
Received date:
31 March 2019
Revised date:
31 August 2019
Accepted date:
2 September 2019
Please cite this article as: Q. Wang, C. Chao and Y. Zhao, Recovery behavior of high ammonium inhibition in a sequencing batch biofilm reactor, Bioresource Technology Reports(2019), https://doi.org/10.1016/j.biteb.2019.100315
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier.
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Recovery behavior of high ammomium inhibition in a sequencing batch biofilm reactor Qian WANG a†, Chunfang CHAO a†, Yingxin ZHAO a,* a School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China †
Q. Wang and C. Chao contributed equally to this article.
*Corresponding author: Yingxin Zhao; School of Environmental Science and Engineering, Tianjin
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University, Tianjin 300072, China. E-mail: [email protected] (Y.Zhao). Tel/Fax: +86 22 2740 6057
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Abstract: Few studies have investigated the process of microbial recovery from wastewater
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inhibited by high-strength ammonium but focused on the inhibition effects only. In this study, one contrast way and four efficient ways were developed and applied to five parallel sequencing batch
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biofilm reactors (SBBRs). The effluent ammonia nitrogen (NH4+-N), nitrite nitrogen (NO2--N),
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nitrate nitrogen (NO3--N), total nitrogen (TN), chemical oxygen demand (COD) and total phosphorus (TP) concentrations were investigated to assess the recovery effects of removal rates as
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well as the recovery mechanism. Results showed that all of these methods have a positive effect, among which introducing algae was optimum for the fast removal recovery of TN and TP within 4 days. And its recovery time is at least 8 days shorter than that in natural recovery. The recovery ways proposed in this study can be potentially applied in the emergency treatment in SBBR system. Key words: Ammonium inhibition, Fast recovery, Rural wastewater, Sequencing batch biofilm reactors
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1. Introduction Rural wastewater treatment has received worldwide attention (Massoud et al., 2009). A large number of untreated rural sewage discharges are disorderly, seriously polluting soil, surface water and groundwater, which affects the safety of drinking water and poses a great threat to rural
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ecological environment. The current comprehensive treatment rate of rural sewage is very low, for example, it is only about 20% in China. Therefore, developing an effective approach to reduce rural water pollution is important and imminent (Wan et al., 2009; Li et al., 2012; Gu et al., 2016).
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Sequencing batch biofilm reactor (SBBR), a combination of traditional activated sludge process
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and biofilm process, is suitable for intermittent discharge of rural sewage and large change of pollutant loading. In our previous study, periodical results have achieved by using SBBR to treat
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rural wastewater in salinized areas (Zhao et al., 2017). A fast start-up with high biofilm attachment
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of 7275.0 mg/L and high removal efficiency of pollutants were demonstrated. From the aspect of
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stable operation, impact loading including heavy metal impact (Wang et al., 2015; Wang et al., 2016), high-strength ammonia shock (Wei et al., 2017) will negatively affect the efficient removal of nitrogen, phosphorus and organic matters. A long-term survey has done to evaluate the characteristics of rural sewage, and it was found that non-point source pollution in storm, high ammonium accumulation in winter, and substandard discharge of industrial wastewater could possibly lead to ammoium inhibition of SBBR system in rural area (Quan and Yan, 2002). Hockenbury and Grady (1997) reported that industrial wastewater containing high ammonia nitrogen entering rural sewage treatment plants inevitably inhibited biological activities, resulting in
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a decline in the performance of biological wastewater treatment systems. High-intensity ammonium nitrogen has a large effect on the removal ratio of nitrogen and phosphorus through biological mechanisms (Mahendraker et al., 2010). Wang et al (2009) found that when the influent chemical oxygen demand/total phosphorus (COD/TP) and chemical oxygen demand/total nitrogen (COD/TN) ratios were 19.9 and 9.9, and the optimum phosphorus and
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nitrogen removal rates could be achieved at 94% and 91%, respectively. In the case of lower COD/TN (3.5), the removal efficiency of nitrogen and phosphorus were significantly reduced. If the ammonium concentration was too high, the nitrifying bacteria would lose their activity (Wu et al.,
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2008; Li and Zhao, 2006), and it took a long time for natural recovery after inhibition.
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Since the hydraulic retention time (HRT) of SBBR can change the aerobic anaerobic time of the
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system, the living environment of microorganisms and its metabolism time are affected
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correspondingly. Muhamad et al. (2012) confirmed that improving HRT is beneficial to the pollutant removal efficiency of SBBR system. In addition, studies have shown that the addition of other
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substances in the system can also improve the removal efficiency of SBBR for TN, TP and COD by affecting the microbial community structure and reproductive characteristics, such as Granular Activated Carbon (GAC) (Osman et al., 2013), Microalgae (Li et al., 2012) and Bioaccelerators (Wang
et
al.,
2015;
Wang
cytokinins and L-aspartate were effective
et
al.,
2016).
It was
ingredients of bioaccelerators.
reported Biotin
that has
biotin, a
good
promoting effect on the growth of microorganisms in activated sludge (Lawson et al., 2000; Oda et al., 2000). Among the cytokinins, 6-benzylaminopurine is widely used, and plays an important role in cell growth, differentiation and other related physiological activities (Singh P, Mohanta T K,
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Sinha A K., 2015). Cokesa et al. (2004) found that L-aspartate can release ammonia during the deamination process, and this metabolite ammonia may be induced by ammonia lyase. Therefore, biotin, cytokinin and L-aspartic acid, were selected as bio-accelerators for further study. Most previous studies have focused on the inhibition effects of high-strength ammonium, while they mainly paid attention to the inhibition and few studies tried to develop effective mothods
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during recovery period to promote bioactivity recovery. This study aims to develop effective recovery ways (natural recovery, extending hydraulic retention time, adding granule activated carbon (GAC), adding bio-accelerator, introducing algae) to relieve high ammonium inhibition of
2. Materials and Methods 2.1. The bioreactor and inoculation
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SBBR system and compare their recovery effects. The recovery mechanism will also be discussed.
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These five SBBRs were inoculated with the activated sludge from a secondary settling tank
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(Jingu wastewater plant, Tianjin, China). In the inoculated sludge, the content of mixed liquor suspended solids (MLSS) was 8220.0 mg/L, and the mixed liquor volatile suspended solids
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(MLVSS) was 5245.0 mg/L. So the rate of MLVSS and MLSS was 0.63, while the sludge volume index (SVI) in inoculated sludge was 64.48 mL/g. The seed sludge were cultivated in five identical SBBRs with 4.25 L working volumes, namely SBBR-1 (natural recovery), SBBR-2 (extending hydraulic retention time for recovery), SBBR-3 (adding GAC for recovery), SBBR-4 (adding bio-accelerator for recovery) and SBBR-5 (introducing algae for recovery). The reactor was made of Plexiglass, and the dimensions of this reactor were 22.0 cm × 15.0 cm × 19.0 cm (diameter × eight × inner diameter). In this study, all of the SBBRs were equipped with a water trap in the center. The water trap has 72 holes, each inserting a spiral fibers (shape like aquatic-grass, 15.0 cm of each). The reactor was covered by a lid with
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Journal Pre-proof holes in it. Microbial growth requires an intermittent anoxic environment, which is manufactured by an air compressor. Each SBBR has two peristaltic pumps for the effluent and influent of the system. The SBBR-1 was set as the control group, and the pollutants removal was recovered by nature. The volume of the added GAC with particle size of 6-8 mm was about 30% of the reactor volumein SBBR-3 to enhance the system performance recovery. For the SBBR-4, the bio-accelerator (0.01
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μg/L biotin, cytokinin and L-aspartic acid) was dosed during the whole recovery phase in the influent synthetic wastewater. The algae (chlorella L166) with the concentration at 1.043 g/L were added into the SBBR-5, the photo period was half-day (12 h light and 12 h dark) and the photo
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intensity was 5000 ± 200 lx in SBBR-5.
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2.2. Experimental operation
The operation of these reactors was divided into three phases, namely culturing phase (1-18
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days), ammonia nitrogen suppressing phase (19-25 days) and recovery phase (26-40 days).
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In the culturing phase, all of the SBBRs were operated in a cycle of 9.0 hours, including four
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phases: influent (0.5 hour), anaerobic (3.0 hours ), aerobic (5.0 hours), effluent (0.5 hours). In influent, there were four kinds of chemicals: NaHCO3 (174.9 mg/L); NH4+-N (42.0 mg/L); COD (420.0 mg/L); TP (6.0 mg/L), and the pH was maintained at 7.0 ± 0.2. There are two stages in the biofilm acclimation process, aerobic and anaerobic. The concentration of dissolved oxygen (DO) was kept at 6.0-7.0 mg/L in the former one and at less than 0.1 mg/L during the latter phase. The temperature of this study was always maintained at 20 ± 1 °C, and the volume used for exchange was 50%. The sign of domestication of inoculated sludge is that the removal efficiency of TP, TN and COD has not changed significantly within 7 days.
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In the ammonium nitrogen suppressing phase, the SBBRs were also operated in the 9.0-h cycle as in the culturing phase and the pollutants concentration in influent were as follows: NaHCO3 (174.9 mg/L); NH4+-N (200.0 mg/L); COD (420.0 mg/L); TP (6.0 mg/L). In the recovery phase, the SBBRs were still operated in the cycle of 9.0 hours as in the culturing phase except the SBBR-2, the SBBR-2 was operated in a cycle of 13.0 hours, including four phases:
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influent (0.5 hour), anaerobic (3.0 hours ), aerobic (9.0 hours), effluent (0.5 hours), as shown in Table 1. The concentration of NaHCO3, NH4+-N, COD and TP in synthetic wastewater prepared with tap water were 174.9 mg/L, 42.0 mg/L, 420.0 mg/L and 6.0 mg/L, respectively. All of the chemical
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reagents used in this study were analytically pure.
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To explain the effect of HRT on the recovery of SBBR system behavior，the variation of COD,
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TN, NH4+-N, nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N) and TP concentration in a total
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operation cycle during the recovery phase were studied, and there were 6 water samples collected from the SBBR-2 every 2.0 h, beginning in anaerobic phase and ending in aerobic phase.
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The adsorption experiment to illustrate the adsorption ratio of COD, TN and TP by the GAC was carried out at 20 ± 1 °C with pH at 7.0 ± 0.2 in a 15 mL sealed plastic tube for 9.0 h. The adsorbent dose was about 15 cm3 and the initial concentration of COD, TN and TP was 420.0 mg/L, 42.0 mg/L and 6.0 mg/L, respectively. 2.3. Analytical methods
The COD was detected by cuvette rapid tests using HACH DR2800 (21259-15, USA). The contents of nitrogen and phosphorus were quantified according to Chinese national standard methods:
TN
(HJ636-2012),
NH4+-N
(HJ535-2009), 6
NO2−-N
(GB7493-87),
NO2−-N
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(HJ/T346-2007), TP (GB11893-89). The MLSS and MLVSS were measured according to the gravimetric method. The temperature and DO were monitored using an online detector (Model 6308DT, China), the pH was detected through a pH meter (Mettler FP20, Switzerland). The concentration of chlorophyll-a was detected according to the specification for oceanographic survey and marine biological survey. The measurements
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mentioned above were performed in parallel three times and the results were averaged. 3. Results and discussion 3.1. Inhibition of high-strength ammonium
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After 5 days of SBBR operation, the COD removal rate in the reactor was nearly 100%. The
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average removal rates of TN and TP in phase I reached 74.16% and 94.12%. Fig. 1 revealed that the
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removal rate of COD and NH4+-N decreased rapidly after the bioreactor is subjected to high-strength
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ammonium afftect. At the end of phase II (25 d) , the removal rate of TN was 34.15%. The percentages of NH4+-N, NO2--N and NO3--N in TN were 76.45%, 8.94% and 13.95%, respectively.
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The obvious decrease of TN removal was attributed to the inhibition of nitrification process. So there was a large amount of NH4+-N stranded and cannot be converted to NO2--N or NO3--N. The similar phenomena was found in Wang’s study, and the high concentration of NH4+-N (200.00 mg/L) inhibited the nitrification reaction with nitrogen removal rate decreased by 40.91% (Wang et al., 2010). On one hand, it interfered with the metabolism of the cells and a relatively long time was taken to show the negative effect. On the other hand, it could destroy the initial oxidizing power of the bacteria in a short time. This deduction was consistent with the findings of Ilies and Mavinic (2001). In addition, ammonia nitrogen was the basic nitrogen source for anaerobic microorganisms,
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but if the concentration is too high, it will have a toxic effect on anaerobic microorganisms, and was not conducive to the formation of biofilm. Ammonium entered the denitrifying bacterial cell by passive diffusion, changing the proton balance of cell. Moreover, the accumulation of intracellular ammonium caused a change in its pH value, which in turn had toxic effects on cells (Yenigün et al., 2013). Therefore, in the biological treatment of sewage, high-strength ammonium conditions
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simultaneously reduced the activity of nitrifying bacteria and denitrifying bacteria. It can be seen from Fig. 1 that after the completion of the phase II, the removal rate of TP was reduced from 97.99% at the phase I to 41.20%. Because the NH4+-N content of the influent water
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was too high, so there was a part of NO3--N residue in the remaining mixture after one cycle of the
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reactor operation. At this time, the COD content in the system was very low, which casused the
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competition between denitrifying bacteria and phosphorus accumulating organisms (PAOs) for
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organic substances. Therefore, only at the end of the denitrification phase, PAOs can release phosphorus when the system completely entered the anaerobic state, which directly affected the
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efficiency of phosphorus release (Xu et al., 2011). Studies have confirmed that under certain conditions, more phosphate release in anaerobic phase could promote the phosphorus absorption by PAOs in aerobic phase. (Chen, 2007), so the high-intensity NH4+-N impact reduced the phosphorus removal ratio of the system or even destroyed it. 3.2. Recovery of the SBBR system 3.2.1. Recovery of the system by nature The natural recovery of the SBBR system was shown in Fig. 1 without changing any operating condition of the reactor. It showed that the removal rate of NH4+-N in the culturing phase was nearly
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the NO3--N concentration gradually returned to the stable value of the culturing phase. As seen in Fig. 1a at the end of the phase II (25 d), there was no significant effect on the COD removal rate of the reactor (Fig. 1a). It can be seen from Fig. 1b that after the concentration of NH4+-N returned to
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the initial concentration (42.00 mg/L), the NH4+-N concentration in the effluent decreased rapidly at
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first and then slowing down. When the reactor was operated for 38 days, the removal rate of NH4+-N was 98.38%, reaching the level before ammonia nitrogen shock. Moreover, in phase III, the
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concentration of NO2--N in the effluent decreased steadily, and NO3--N increased first with the highest value at 31 days and then decreased (Fig. 1c). It indicated that the activity of nitrifying
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bacteria was first restored compared to denitrifying bacteria. The removal rate of TN reached a maximum of 78.64% as phase I at 38 days. For TP, the removal efficiency (94.60%) did not recovered to phase I (98.47%) until the end of phase III, indicating the degree of recovery of PAOs activity was limited in 15 days. 3.2.2. Recovery of the system by extending hydraulic retention time (HRT) As shown in Fig. 2，the concentration of NH4+-N and NO2--N didn't change obviously during the anaerobic phase, while the concentration of NO3--N decreased significantly, indicating effective denitrification at this stage. The degradation of COD was also observed in the anaerobic phase due
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to the fact that denitrifying bacteria were heterotrophic microorganisms. There was a small increase in TP concentration during the anaerobic phase and a significant decrease in the aerobic phase (Fig. 2e), confirming that the biological phosphorus removal process in the SBBR system was a typical PAOs mechanism for phosphorus release and uptake. Win et al. (2016) and Zhang et al. (2016) had confirmed that the performance of micropollutant
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degradation and wastewater treatment can be improved by changing HRT duration in MBR system, because the change of HRT affects the relationship between bacterial community and system efficiency. In this study, after the aerobic time changes from 5 h to 9 h, the recovery effect of the
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SBBR system was significantly improved. Comparing to SBBR-1 the time required for TN and TP
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removal was reduced by 7 days and 9 days. As shown in Fig. 3, at the first day of the phase III (26
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days), the concentration of NH4+-N in the reactor decreased to 10.68 mg/L. NH4+-N and NO3--N
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accounted for 27.63% and 69.26% of TN, respectively. Obviously increasing the aerobic time increased the action time of the nitrifying bacteria, and the nitrogen conversion process in the
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nitrification stage was promoted. At the same time, the increase of aerobic time also provided sufficient time for PAOs to take up phosphate from wastewater, which promoted the phosphorus removal effeciency of the recovery system. 3.2.3. Recovery of the system by adding granular activated carbon (GAC) On the second day of the phase III (day 27 of system operation), the concentration of NO3--N immediately decreased from 50.69 mg/L to 12.73 mg/L (Fig. 4c), accounting for 65.01% of TN, indicating the activity of denitrifying bacteria was rapidly recovered in a short time after the addition of GAC. At day 31, the removal rate of effluent NH4+-N was nearly up to 100% (Fig. 4b), which
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was 7 days shorter than that in SBBR-1. It revealed that the activity of nitrifying bacteria was also significantly improved. At day 31 and 37 of the reactor operation, the removal rates of TN and TP were substantially restored to the levels as phase I. Due to the high specific surface area and porosity, GAC
had
strong
adsorption
capacity.
A verification
experiment was conducted to
demonstrate the adsorption ability of GAC on COD, TN and TP in wastewater, as shown in Table
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2. Results showed that nearly 30% removal efficiency of COD, TN and TP was acheived by GAC adsorption. This partly contributed to the improvement of the recovery process. Moreover, the rough texture of GAC was beneficial to the adhesion of microorganisms, providing an excellent carrier for
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the formation of biofilm. Similar study reported that the growth rate of autotrophic nitrifying
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bacteria in high-strength ammonium wastewater was severely limited, and the growth of particulate
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aerobic sludge was also limited (Tao et al., 2017). Nevertheless, the addition of GAC promoted the
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formation of particulate aerobic sludge (Wei et al., 2013). From Fig. 4e, d, it can be clearly observed that the recovery of the nitrogen removal after GAC introduction was obviously rapid than that of
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phosphorus, probably because a variety of bacteria have a competitive relationship in the process of forming biofilm on the surface of GAC, and PAOs was inferior in competition. 3.2.4. Recovery of the system by adding bio-accelerator After the addition of the bio-accelerator, the concentrations of NH4+-N, NO2--N and NO3--N in the effluent showed a rapid decline at the same time. At 31, 26 and 29 days, their concentrations recovered to the level of phase I (Fig. 5b, c, d), and the recovery time required for NH4+-N removal (96.6%) was 7 days shorter than that in SBBR-1. It was clear that nitrogen removal was significantly improved with the activities of nitrifying bacteria and denitrifying bacteria quickly recovered. The
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removal rates of TN and TP reached 80.06% and 96.6% at 35 and 34 days, respectively, which recovered to the level as phase I (Fig. 5d, e). It can be seen that the addition of bio-accelerator was beneficial to the rapid recovery of microorganisms after inhibition by high-intensity ammonium. After being impacted, ammonium diffuses into the cells and accumulates through passive diffusion, thereby breaking the balance of
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protons. The biopromoter (cytokinin) contains 6-mercaptoaminopurine, which can cause changes in a series of conductive substances in the cell (Inoue et al., 2001). It is conducive to rebuild the internal and external balance of cells and alleviating the poisoning state. The special function of
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growth factors also contributed to the recovery phase. For example, biotin can improve the ability of
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activated sludge flocs (Oda et al., 2000). Cytokinins can promote the growth and reproduction of
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nitrifying bacteria. Miljkovic et al. (2015) found that a substrate containing cytokinins can increase
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the growth rate and fermentation rate of microorganisms. At the end of the reactor run (40 days), the removal efficiency of TP reached 99.67%, slightly
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higher than the pre-impact value of 96.54%. The concentration of NO3--N in SBBR-4 was maintained at 6 mg/L after the phase III (Fig. 6c), which was much lower than 9 mg/L in SBBR-1. Moreover, compared with SBBR-1, the recovery of TN and TP removal rates were advanced by 3 days and 6 days, which may be due to the fact that the addition of bio-accelerators is more effective in improving the activity of PAOs. 3.2.5. Recovery of the system by introducing algae After adding algae to the system, similar to the result of SBBR-1, the concentrations of effluent NH4+-N and NO2--N were continuously reduced in the initial stage of the recovery phase, and
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The removal rates of TN and TP were recovered to 79.93% and 98.04% during the acclimation period as shown in Fig. 6d, e. The time for recovery was reduced by 7 and 10 days compared to natural recovery conditions. At the end of the recovery period, the removal efficiency of TN and TP
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reached 88.28% and 98.97%, both higher than that in phase I. Studies had shown that the removal
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efficiency of total nitrogen and phosphoric acid in algae bacterial particle systems (50.2% and
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35.7%) was better than that of pure aerobic particle systems (32.8% and 25.6%) (Liu et al., 2018).
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The introduction of microalgae to SBBR can promote the recovery of the system while also improve the removal rate of TN and TP. Because this method increased the amount of organisms in
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the wastewater, at the same time, a microalgae-bacterial symbiosis system was formed. The CO2 produced by bacteria provides the raw material for photosynthesis of microalgae, and the O2 produced by light and action in turn promotes the metabolic process of bacteria, which is beneficial to rapid recovery. Tang et al. (2017) demonstrated that algae-assisted SBBR systems could effectively remove TN and TP. 3.3. Comparison of different recovery methods The time required for the five recovery methods to restore the removal efficiency of NH4+-N, TN and TP in the reactor to the level before impacted was listed in Table 3. As shown in Table 3, the
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recovery time used by SBBR-5 was the shortest. Furthermore, when the system stopped as it was running for 40 days, the removal efficiency of TN and TP reached 88.28% and 98.97%, both higher than the removal efficiency during the acclimation period. The microbial community in the sewage interacts with the microalgae, which promotes the biological treatment of the sewage. Hernandeze et al. (2013) treated the high-ammonia nitrogen concentration of pig-raising wastewater by the
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bacterial-algal symbiosis system. The removal efficiencies of nitrogen and phosphorus were 82.7% and 58.0%. Moreover, algae are autotrophic organisms, which can synthesize their own complex organic components using nitrogen and phosphorus. In addition, algae cells have high protein,
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amino acid content and high production rate. They can be reused as animal feed and bait after
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harvesting. Therefore, the bacterial algae system is effective and can be potentially applied in the
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recovery of high-ammonia-inhibiting biological process.
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4. Conclusion
In this study, five ways were developed to promote the recovery efficiency of SBBR which
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were inhibited by high-strength ammonium. Results showed 200.00 mg/L NH4+-N inhibited more than 50.00% removal efficiency of NH4+-N, TN and TP within 2 days. Comparing to natural recovery, extending HRT, adding GAC or bio-accelerator, introducing algae was most effective with recovery time for TN and TP both in 4 days. Moreover, it further improved the removal efficiency of TN and TP to 88.28% and 98.97%, which were both higher than that in the initial acclimation period. Acknowledgements
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This work was supported by the National Key R&D Program of China (Project
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No.SQ2018YFGH000422).
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References Chen, Q., 2007. Factors of influencing biological denitrification and dephosphorization. Pollut. Ctrl. Technol. Cokesa, Z., Knackmuss, H., Rieger, P., 2004. Biodegradation of all stereoisomers of the EDTA substitute iminodisuccinate by Agrobacterium tumefaciens BY6 requires an epimerase and a
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stereoselective C-N lyase. Appl. Environ. Microb. 70, 3941-3947. GB7493-87. Water quality-Determination of nitrogen (nitrite) -spectrophotometric method. Ministry of Environmental Protection. China. GB11893-89.
Water
quality-Determination
of
total
phosphorus-Ammonium
molybdate
e-
spectrophotometric method. Ministry of Environmental Protection. China. Gu, B., Fan, L., Ying, Z., Xu, Q., Luo, W., Ge, Y., Scott, S., Chang, J., 2016. Socioeconomic
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constraints on the technological choices in rural sewage treatment. Environ. Sci. Pollut. R. 23, 20360-20367.
al
HJ636-2012. Water quality-Determination of total nitrogen-Alkaline potassium persulfate digestion
HJ535-2009.
Water
ur n
UV spectrophotometric method. Ministry of Environmental Protection. China. quality-Determination
of
ammonia
nitrogen-Nessler’s
reagent
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spectrophotometry. Ministry of Environmental Protection. China. HJ/T346-2007. Water quality-Determination of nitrate-nitrogen-Ultraviolet spectrophotometry. Ministry of Environmental Protection. China. Hernández, D., Riano, B., Coca, M., García-González, M., 2013. Treatment of agro-industrial wastewater using microalgae-bacteria consortium combined with anaerobic digestion of the produced biomass. Bioresour. Technol. 135, 598-603. Hockenbury, M.R., Grady, C.P.L., 1977. Inhibition of nitrification-effects of selected organic compounds. Journal. 49, 768-777. Ilies, P., Mavinic, D.S., 2001. The effect of decreased ambient temperature on the biological nitrification and denitrification of a high ammonia landfill leachate. Water Res. 35, 2065-2072. 16
Journal Pre-proof Inoue, T., Higuchi, M., Hashimoto, Y., Seki, M., Kobayashi, M., Kato, T., Tabata, S., Shinozaki, K., Kakimoto, T., 2001. Identification of CRE1 as a cytokinin receptor from Arabidopsis. Nature. 409, 1060-1063. Lawson, P., Collins, M., Schumann, P., Tindall, B., Hirsch, P., Labrenz, M., 2000. New LL-diaminopimelic acid-containing actinomycetes from hypersaline, heliothermal and meromictic Antarctic Ekho Lake: nocardioides aquaticus spnov and friedmannielly lacustris spnov. Syst. Appl. Microbiol. 23, 219-229.
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Li, H., Hao, M., Liu, J., Chen, C., Fan, Z., Wang, X., 2012. Effect of pH on biologic degradation of Microcystis aeruginosa by alga-lysing bacteria in sequencing batch biofilm reactors. Front. Env. Sci. Eng. 6, 224-230.
Li, J., Zhao, Q., 2006. Study of factors influencing ammonia nitrification. J. China Univ. Min.
e-
Techno. 35, 120-124.
Pr
Liu, L., Zeng, Z., Bee, M., Gibson, V., Wei, L., Huang, X., Liu, C., 2018. Characteristics and performance of aerobic algae-bacteria granular consortia in a photo-sequencing batch reactor. J.
al
Hazard. Mater. 349, 135-142.
Li, Z., Zhang, J., Chen H, Zhang, L., Kang, Q., Feng, Y., 2012. Water pollution situation and impacts
ur n
in rural China. Agr. Sci. Tech. 13, 1055-1059. Muhamad, M., Abdullah, S., Mohamad, A., Rahman, R., Kadnum, A., 2012. Effect of hydraulic
Jo
retention time (HRT) on pentachlorophenol (PCP) and COD removal in a pilot GAC-SBBR system for the post-treatment of recycled paper mill wastewater. Desalin. Water Treat. 48, 50-59. Miljkovic,
D.,
Blazevski,
J.,
Petkovic,
F., Djedovic, N., Momcilovic, M.,
Stanisavljevic, S., Jevtic, B., Stojkovic, M.M., Spasojevic, I., 2015. A comparative analysis of multiple sclerosis relevant anti-inflammatory properties of ethyl pyruvate and dimethyl fumarate. J. Immunol. 194, 2493-2503. Mahendraker, V., Mavinic, D.S., Rabinowitz, B., Hall, K.J., 2010. The impact of influent nutrient ratios and biochemical reactions on oxygen transfer in an EBPR process-a theoretical explanation. Biotechnol. Bioeng. 91, 22-42. 17
Journal Pre-proof Massoud, M.A., Tarhini, A., Nasr, J.A., 2009. Decentralized approaches to wastewater treatment and management: Applicability in developing countries. J. Environ. Manage. 90, 652-659. Osman, W., h, S., Mohamad, A., Kadhum, A., Rahman, R., 2013. Simultaneous removal of AOX and COD from real recycled paper wastewater using GAC-SBBR. J. Environ. Manage. 121, 80-86.Abdulla Oda, Y., Slagman, S., Meijer, W., Forney, L., Gottschal, J., 2000. Influence of growth rate and starvation on fluorescent in situ hybridization of rhodopseudomonas palustris. Fems Microbiol. Ecol. 32, 205-213.
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Quan, W., Yan, L., 2002. Effects of agricultural non-point source pollution on eutrophica-tion of water body and its control measure. Acta Ecologica Sinica. 22, 291-299. Singh, P., Mohanta, T., Sinha, A., 2015. Unraveling the intricate nexus of molecular mechanisms governing rice root development: OsMPK3/6 and Auxin-Cytokinin interplay. Plos One. 10,
e-
230-234.
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Tang, C., Zuo, W., Tian, Y., Wang, Z., Zhang, J., He, Z., 2017. Enhanced nitrogen and phosphorus removal from domestic wastewater via algae-assisted sequencing batch biofilm reactor.
al
Bioresour. Technol.
Tao, J., Qin, L., Liu, X., L,i B., Chen, J., You, J., Shen, Y., Chen X., 2017. Effect of granular
2017, 236:60-67.
ur n
activated carbon on the aerobic granulation of sludge and its mechanism. Bioresour. Technol.
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Wang, F., Ding, Y., Ge, L., Ren, H., Ding, L., 2010. Effect of high-strength ammonia nitrogen acclimation on sludge activity in sequencing batch reactor. J. Environ. Sci. 22, 1683-1688. Wang, Y., Ji, M., Zhao, Y., Zhai, H., 2016. Recovery of nitrification in cadmium-inhibited activated sludge system by bio-accelerators. Bioresour. Technol. 200, 812. Win, T.T., Kim, H., Cho, K., Song, K.G., Park, J., 2016. Monitoring the microbial community shift throughout the shock changes of hydraulic retention time in an anaerobic moving bed membrane bioreactor. Bioresour. Technol. 202, 125–132. Wan, D., Liu, H., Qu, J., Lei, P., Mao, S., Hou, Y., 2009. Using the combined bioelectrochemical and sulfur autotrophic denitrification system for groundwater denitrification. Bioresour. Technol. 100, 142-148. 18
Journal Pre-proof Wei, D., Xue, X., Chen, S., Zhang, Y., Yan, L., Wei, Q., Du, B., 2013. Enhanced aerobic granulation and nitrogen removal by the addition of zeolite powder in a sequencing batch reactor. Appl.
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Microbiol. Biot. 97(20):9235-9243.
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Figure Captions Fig.1 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2--N and NO3--N, (d) TN, (e) TP in SBBR-1 Fig.2 The variation of (a) COD, (b) TN, (c) NH4+-N, (d) NO3--N, NO2--N, (e) TP concentration in a total operation cycle during the recovery phase in SBBR-2
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Fig.3 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-2
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Fig.4 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-3
Fig.5 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-4
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Fig.6 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and
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NO3--N, (d) TN, (e) TP in SBBR-5
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Table Captions Table 1 The cycle time in recovery phase. Table 2 Water quality change before and after adsorption of GAC.
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Table 3 Time required for recovery efficiency in different reactors.
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Fig.1 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2--N and NO3--N, (d) TN, (e) TP in SBBR-1.
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Fig.2 The variation of (a) COD, (b) NH4+-N, (c) NO3--N, NO2--N, (d)TN, (e) TP concentration in a total operation cycle during the recovery phase in SBBR-2.
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Fig.3 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-2.
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Fig.4 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-3.
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Fig.5 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-4.
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Fig.6 Effluent concentration and removal efficiency of (a) COD, (b) NH4+-N, (c) NO2- -N and NO3--N, (d) TN, (e) TP in SBBR-5.
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Anaerobic
Aerobic
Effluent
9.0-h
0.5 h
3.0 h
5.0 h
0.5 h
13.0-h
0.5 h
3.0 h
9.0 h
0.5 h
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TP（mg/L）
pH
Before
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42.63
6.35
7.64
After
323
28.15
4.44
8.27
Removal efficiency
29.47%
33.97%
30.06%
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COD（mg/L）
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Journal Pre-proof Table 3 Time required for recovery in different reactors. SBBR-1
SBBR-2
SBBR-3
SBBR-4
SBBR-5
NH4+-N
38 d
31 d
31 d
31 d
29 d
TN
38 d
31 d
31 d
35 d
31 d
TP
40 d
31 d
37 d
34 d
30 d
SBBR-1 to SBBR-5 represent: natural recovery; extending HRT recovery; adding GAC recovery; adding bio-accelerator recovery; adding algae recovery.
Conflict of interest
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The authors declare that they have no conflict of interest.
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Highlights 1. High ammonium reduced the TN and TP removal efficiency of TN and TP by 50%. 2. Five ways were proposed to recover the ammonium inhibition of SBBR. 3. Introducing algae was optimum for the fast removal recovery of TN and TP. 4. The SBBR system could be recovered in 4 days after introducing algae.
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