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Analysis of parameters for leachate treatment in a greenhouse system
International Journal of Sustainable Built Environment (2017) xxx, xxx–xxx
H O S T E D BY
Gulf Organisation for Research and Development
International Journal of Sustainable Built Environment ScienceDirect www.sciencedirect.com
Original Article/Research
Analysis of parameters for leachate treatment in a greenhouse system Ana Laura Go´mez Blasco a, Constantino Gutie´rrez b, Andre´s Armando Sa´nchez Herna´ndez c, Margarita Teutli Leo´n a,⇑ a
Facultad de Ingenierı´a, Beneme´rita Universidad Auto´noma de Puebla, Mexico b Universidad Nacional Auto´noma de Me´xico, Mexico c Facultad de Arquitectura, Beneme´rita Universidad Auto´noma de Puebla, Mexico Received 13 May 2016; accepted 8 February 2017
Abstract In this paper is presented an approach for landfill leachate treatment using enhanced natural evaporation. Experimental set up considered using a greenhouse pilot prototype placed into the municipal landfill of Puebla city, Me´xico. The greenhouse was built with a basement surface enough to place 9 trays with leachate. Treatment follow up was done through the following parameters: air temperature inside and outside the greenhouse; leachate temperature at surface and middle liquid height. Results of the first set of experiments defined a minimal initial liquid height of 20% in respect to the tray height; the 2nd set allowed defining optimal evaporation rate conditions evaluated in respect of a tray placed outside, considered as reference of 100% efficiency (blank), obtained results showed that morning and night processes provided efficiencies up to 2 times the reference; otherwise, afternoon measurements showed similar temperature values inside and outside. In general collected data at winter season provided efficiencies between 82% and 147%, in periods of 24 h, it was observed that higher liquid reductions took place at North, and lower ones at the South positions. Based on these results it was proposed a 20 days experiment, using stagnant (E) and recharge (R) conditions referred to the blank (L), the R process showed greater efficiency (168%) than the stagnant one (158%). Leachate chemical characterization indicates that pH is highly stable; while total solids, chemical oxygen demand, sulfate and chloride exhibit an increase in concentration reaching values of 1.2–2.5 times the initial concentration, phosphate was the only parameter exhibiting a decreasing trend ending with 40% of its initial concentration. Ó 2017 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.
Keywords: Landfill; Leachate; Evaporation; Greenhouse; Tray position
1. Introduction Actually urban solid wastes are disposed in landfills, where the inherent organic matter decomposition produce leachate liquids, and their amount is enhanced by liquids ⇑ Corresponding author.
E-mail address: [email protected] (M. Teutli Leo´n). Peer review under responsibility of The Gulf Organisation for Research and Development.
input into the confining cells; liquids come from external sources like runoff. Wrong actions in handling leachate liquid usually represent a contamination risk and a source of infections, therefore it is mandatory to implement actions to improve efficiency of applied treatment. There are reports about applied methods for leachate treatment, which at first approach operate under aerobic or anaerobic conditions (Cleber et al., 2014; Ismail and Tawfik, 2016), in treatment design facilities it has been con-
http://dx.doi.org/10.1016/j.ijsbe.2017.02.008 2212-6090/Ó 2017 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
sidered using natural systems like ponds and artificial wetlands (Ogata et al., 2015; Mojiri et al., 2016), while other systems accounted for leachate recirculation and evaporation (Huang et al., 2016; He et al., 2015). Research to improve leachate treatment has made use of membrane bioreactors, reverse osmosis, (Sanguanpak et al., 2015), electrocoagulation (Contreras et al., 2009), and flocculation (Raghab et al., 2013). Recent research approaches have explored applying Advance Oxidation Process (AOP) which involves generation of strong oxidants addressed to reduce the chemical oxygen demand (Silva et al., 2015; Hassan et al., 2016; Hilles et al., 2016; Zhou et al., 2016), also there are reports of treatments that use more than one technique (Amor et al., 2015; Wallace et al., 2015; Liu et al., 2015; Wu et al., 2015), some treatment options, based on unit operations, ranges from primary to tertiary treatment (Oulego et al., 2015; Kumari et al., 2016), while others have made incursion on nanotechnology (Hu et al., 2016; Zhang et al., 2016). From above mentioned reports it becomes evident that choosing a methodology for leachate treatment usually is a process defined by factors like: leachate chemical characteristics, site location, local weather, available land space for infrastructure, and the effluent final use, easiness in operation as well as inversion, operation and maintenance costs. There is a recent report of Beyouncef et al. (2016) in which they mention that evaporation (natural or forced) has not received the expected attention, especially in warm climate countries; they reported the design and implementation of a small scale forced evaporation tub and its comparison to a natural evaporation tub. They mention that key factors to accelerate leachate evaporation are the surface exposure to sunlight, stirring effect and aeration, but also they recognize that one of their minuses is the electric power consumption to operate both the agitator and aeration fan. Use of natural or induced evaporation should result in a reduction of leachate liquid volume, providing a sludge rich in salt and organic matter, which can either be returned to a final disposal cell or receive alternative treatment. Therefore, landfill operation should be favored since a concentrated sludge is easier to handle and it requires less space; so far, these actions imply an economical benefit. Research work reported in this paper was developed in Me´xico, for the Puebla city landfill, which is located at 2018 m above sea level, this is a site with an estimated area of 916,826.747 m2, whose UTM coordinates are between 590,578.4389-590,665.3343 East, and 2,098,706.79712,098,818.2245 North. Actual leachate production of 75 m3 per day is treated in 3 evaporative ponds (3000 m3 of installed capacity), 33% of treated leachate is recirculated to the active cells to provide humidity, and the rest (67%) are sent to a Waste Water Treatment Plant furnished with biological treatment for both sludge and liquid. Typical weather at Puebla is mild and semi humid, with an average of 5–40 mm daily precipitation during rainfall
season (from May to October), average temperatures range between 12 and 18 °C, with a minimum of 2 °C (at winter nights) and a maximum of 33 °C (at noon in spring). Also, official reports of wind patterns for Puebla city mention that there is presence of katabatic winds between 5 and 11 h running from North and North East to the South, these winds provide fresh and dry air; otherwise anabatic winds are present from 11 to sunset running from south to the north providing wet and warm air: additionally from sunset to sunrise there is presence of a light wind coming from the East. About solar intensity, there is a report (Ramos and Aguilar, 2005) which estimates that Puebla receives solar energy at the high atmosphere level with an estimated solar constant of 2 cal cm 2 min 1 obtained by correlating isotherms and isohyects data obtained in June 2004. Main goal in this project is to take advantage of weather conditions at Puebla to propose a leachate treatment at the landfill site, in which the leachate could be concentrated by enhanced evaporation. An experimental greenhouse was built at the landfill area with the purpose of evaluate how much leachate evaporation is increased by using a greenhouse installation. The first stage considered short time experiments to get enough data for defining optimal operating conditions, and the second stage was a long period experiment (20 days) to evaluate how the optimal conditions work for enhancing evaporation. 2. Materials and methods For designing and operating a greenhouse, the following external parameters should be accounted: amount of leachate to be treated, available space, site meteorological factors including latitude and altitude, solar radiation, temperature, relative humidity, presence of cloudiness, fog, evaporation, precipitation, as well as speed and direction of wind. These external factors will determine the greenhouse internal surface, roof slope and materials to be used; as well as optimal design to get the best conditions for internal climatic factors temperature, evaporation, humidity and ventilation. 2.1. Selection of materials for greenhouse construction Experimental greenhouse prototype construction should consider recommendations like the following ones: (a) walls and roof should be made of high transmittance materials (Szanto´ et al., 2011); (b) the slope of the roof should be designed according to the site latitude, since the maximum solar radiation intensity is captured with a perpendicular plane to the incident ray (Garcı´a-Badell, 2003); accounting for this recommendation the pilot greenhouse lower height wall was placed in the South position, and the higher at North, the last wall required been furnished with an aluminum cover, and the floor with a geomembrane which represents a black body, by which the bottom temperature in the greenhouse should be increased. Imple-
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
menting these recommendations allowed increasing the efficiency in capturing thermal energy from either albedo, walls or roof; (c) the greenhouse should be provided with a ventilation system, in order to assure that saturated air will be replaced by fresh air (Szanto´ et al., 2011), ventilation array should be such that air displacement takes place at a minimal ratio, so the greenhouse effect is barely constant during the whole day. It was observed that at Puebla landfill, it happens that both in-situ temperature and humidity dropped to low values, at afternoon hours, also the wind speed increases to significant values, therefore special measures were taken for assuring that at night the fresh air input into the greenhouse was enough for creating inner turbulences, which will compensate the heat loss due to air temperature drop. In Tables 1–3 is reported greenhouse technical information about construction materials, dimensions and implementation of the ventilation system. In Fig. 1 there is a picture of the pilot greenhouse set up at Puebla Landfill. Physical specifications of trays placed inside the greenhouse are reported in Table 4; and Fig. 2 is a picture of the experimental tray array inside the greenhouse. 2.2. Experimental design The methodology applied in this project consists in doing several experiments focused to discriminate if the greenhouse internal microclimate is adequate to provide the required evaporative conditions. Leachate evaporation was estimated by the average lowering in hydraulic liquid height at each tray, also leachate temperature was registered at two positions: one at the liquid surface and the other at a predefined height (134 mm from surface); also, it was accounted registering temperature inside and outside the greenhouse. It was estimated that the evaporation process should be sensitive to the hydraulic liquid depth in each tray; therefore the first set of experiments was run using 50, 100, 150, 200, 250, 300, 350, 400 and 415 mm of liquid height; placing trays in a parallel array, so far every tray was subject to the same climatic conditions. Since evaporative process could be favored in certain zones of the greenhouse; then other experiments were focused on finding a relationship between evaporation and tray position respect to the solar radiation incidence angle over the greenhouse basement. For this 2nd set of experiments all trays started with the same hydraulic liquid depth (350 mm); and a blank was a tray having the same Table 1 Greenhouse construction materials. Structure
Metallic tubes
Roof and walls Floor North wall (inside)
Transparent plastic 400 Geomembrane Aluminum sheet cover
3
Table 2 Pilot greenhouse dimensions. Base
180 cm 210 cm
Height 1 Height 2 Roof slope
150 cm 218 cm 19°
liquid height but placed outside the greenhouse, this tray simulated the process that could take place at a retention pond. Obtained average evaporation rates were analyzed by day period and tray position inside the greenhouse. Finally, another set of experiments (#3) were run considering a batch sequence in which the leachate was either stagnant (no-recharge) or recharged at fixed times; both conditions were tested simultaneously. For this experiment, 6 trays were used: 3 were left stagnant and the other 3 were recharged up to reach the initial hydraulic liquid height, this procedure took place each time that it was registered a 10% height loss. In this set the reference was a set of trays placed outside the greenhouse under the stagnant and recharge conditions. In this experiments, register of physical parameters included: temperature (T, °C); hydrogen potential (pH), electrical conductivity (EC, mS cm 1). And some physicochemical ones like: total solids (TS, mg L 1), chemical oxygen demand (COD, mg L 1), alkalinity (ALK, mg L 1), chloride (Cl, mg L 1), turbidity (NTU), phosphates (PO4, mg L 1), sulfates (SO4, mg L 1), and chemical oxygen demand (COD, mg L 1). The first and second experiments took place during winter season, while the third one occurred in spring season. In Table 5 are consigned the field experimental conditions. 3. Results and discussion 3.1. Determination of leachate optimal hydraulic liquid depth (Experiment 1) In Table 6 are reported average liquid height reduction. Trays exhibiting higher evaporation during daylight (Dtd) were the ones with initial height of 150, 300 y 415 mm. Otherwise, at night the trays with greater liquid height reduction (Dtn) were the ones with initial height of 100, 200, 250, 350 y 415 mm. When adding day and night (DtT) the observed reductions, it is observed that the tray with minor total evaporation was the one with lower initial hydraulic liquid height (50 mm); most of the trays with initial liquid height between 100 and 400 mm exhibit an average reduction of 6–7 mm per day. The tray with the maximum initial volume was the one of highest evaporation, reaching almost twice the evaporation obtained with the others; although only 9 mm was the difference in respect of the immediate previous one, therefore liquid height reduction cannot be direct consequence of the initial liquid height. It was expected that the tray with the lower liquid content would have the higher evaporation, but this tray was
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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Table 3 Greenhouse ventilation system. Period
Location
Night
Day
North South East West
South East
Up Up Down Up Down Up Center Center
Amount
Dimensions (cm)
Base percentage %
5 3 3 2 3 3 1 1
3 10 3 10 35 3 10 35 3 10 50 180 50 210
0.40 0.24 0.12 0.16 0.12 0.24 23.81 27.78
Trays with the higher evaporation rate were the ones starting with 150, 300 and 415 mm of liquid height, these trays were at the North position inside the greenhouse, therefore it can be concluded that tray location is important, as well as the enhancing factor exerted by light reflected at the aluminum covered wall at the North. 3.2. Liquid height reduction efficiency as a function of tray location inside the greenhouse (Experiment 2)
Fig. 1. Greenhouse pilot picture.
Table 4 Experimental trays dimensions. Width
36 cm
Large Height Material
56 cm 43 cm Transparent plastic
Fig. 2. Experimental tray array inside the greenhouse.
the one with the lower height reduction, fact that it is attributed to its position near the south wall, plus its low liquid height does not allowed being agitated by the night wind.
In this experiment all trays started with 350 mm of liquid height. As in experiment 1 data were collected at day and night, for better visualization it was proposed a color scale for representing registered hydraulic height measurements. It was chosen a red scale for daylight, grey scale for night and a blue scale for the total. In Fig. 3 are represented the assigned values for each color scale. This color scale has been applied in Fig. 4, where it is represented the liquid height reduction as function of tray position inside the greenhouse, array description in vertical direction goes South (base), Center, and North (aluminum wall), while in horizontal direction is described as West (left), Center and East (right), the reference is the tray outside the greenhouse (separate rectangle). As it can be observed during day time (red scale) the higher reductions are obtained at the North an especially at the West side; while at night (grey scale) higher values occur in the center and at the East side; combined observations (blue scale) show that height reduction exhibit an increasing trend from South to North. Taking into account the same distribution, in Table 7 are reported estimated average rates of liquid height reduction (mm-h 1) for each period of the day (morning, afternoon and night). In this Table it is evident that morning evaporation rates were higher for trays inside the greenhouse at the Center West and North positions, while that one placed at the South West showed an evaporation rate similar to the blank (0.63), but surprisingly at the afternoon this tray showed the higher rate (1.60), even slightly higher than the blank (1.40); otherwise the one at the Center West position is practically null (0.0). It is worthy to mention that at night only the Center West and the North East trays got rates similar to the blank, and all others overcome the one of the blank, which means that the implemented ventilation system works fine.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
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Table 5 Experimental methodology. Test
Monitoring parameters
Monitoring frequency
Testing time
1. Optimal hydraulic liquid height determination 2. Liquid height reduction in function of its position inside the greenhouse 3. Stagnant versus recharge
Liquid height measurement Temperature at liquid surface Average liquid temperature, registered at 134 mm down from surface Greenhouse internal microclimate temperature Outside temperature at the experimental site T, pH, EC, TS, ALK, Cl, NTU, PO4, SO4 and COD
9:00, 13:00, 17:00, 20:00 h 9:30, 11:00, 12:30, 14:00, 15:30, 20:00 h 9:00, 13;00, 17:00 h
24 h 24 h
in the range of 82–111%. In general, 44% of the trays got efficiencies higher than 100% which is the blank value. About the leachate surface temperature, there is a direct relationship with tray position inside the greenhouse. Lower values belong to trays placed at the South; while those at the North not only were the ones having the highest values; but also these trays got the faster increments in temperature, reaching values above the average inner greenhouse temperature, this response is attributed to the closeness with the aluminum covered wall. Otherwise, leachate left outside the greenhouse exhibit a similar trend in temperature response to the ones inside, but global temperature raise was smaller. For this tray happened that at 13:00 h temperature taken at middle height was close to the one registered at the surface, also both temperatures were up to 10 °C higher than the air temperature. It is assumed that this higher leachate temperature contributed to increase the evaporation, in consequence this tray exhibited a liquid height reduction during afternoon period.
Table 6 Average liquid height reduction in experiment 1. Location
t0 (mm)
Dtd (mm)
Dtn (mm)
DtT (mm)
South East East North East South Center North South West West North West
50 100 150 200 250 300 350 400 415
4.0 2.0 5.0 2.0 3.0 5.0 3.0 4.0 7.0
0.0 5.0 1.0 4.0 4.0 2.0 4.0 2.0 8.0
4.0 7.0 6.0 6.0 7.0 7.0 7.0 6.0 15.0
t0: initial liquid height. Dtd: Average height reduction during daylight. Dtn: Average height reduction during night. DtT: Average height reduction per day.
It is remarkable that under the operating greenhouse conditions, the period with major contribution to the liquid height reduction was the morning one in which 89% of the trays got evaporations higher than the blank, at the afternoon results are really poor, and at night 78% of the trays got evaporation higher than the blank. Also results from all trays evidence that the North West position is the one having the greater evaporation during the morning; during the afternoon evaporation rates have not meaningful differences in respect to the blank tray placed outside; and during night time the greater evaporations were found at the Center East position. An average rate is reported at the last column by adding liquid height reductions observed in a 24 h period, these values indicate that 44% of leachate trays inside the greenhouse got greater evaporation than the blank outside. Efficiencies of liquid height reduction are shown in Table 8 these were estimated taking the blank as 100%. Attending to the average efficiency (last column), it is observed that higher evaporation correspond to trays placed at the North whose efficiency is between 110% and 137%, while the Center and South provide very close values ay (mm)
9.5
Night (mm)
5.5
Total (mm)
12.5
8.0 12.0
3.3. Comparison of stagnant versus recharged process (Experiment 3) For this step, it was considered a period of 20 days and experiments were run with recharging and stagnant conditions inside the greenhouse, and the blank outside. The recharge was done on the 4, 9 and 15 day. In Fig. 5 is presented the behavior profile of the liquid height reduction under the three process conditions, being R = average daily height reduction of internal trays with recharge; E = Average daily height reduction of stagnant internal trays; L = average height reduction of leachates outside the greenhouse. In general, for all days, leachate height reduction was greater inside the greenhouse than the one registered outside. On the 5th day, there was presence of condensation inside the structure. At the 10th day, it took place a rainfall 7.0
5.0
6.5 4.5
11.5
20 days
11.0
6.0
5.5
3.0 10.5
10.0
2.5 9.5
8.5
Fig. 3. Basic color scale for comparison of the liquid height reduction in trays.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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Average leachate height reduction during day (mm)
Average leachate height reduction during night (mm)
(aluminum wall)
(aluminum wall)
Average leachate height reduction per day (mm) (aluminum wall)
Fig. 4. Average leachate height reduction per tray as function of its location inside the greenhouse.
Table 7 Leachate height reduction rates per periods of the day. Location
Height reduction rate (mmhr 1) Morning
Afternoon
Night
Average
South East South South West Center East Center Center West North East North North West Outside
1.13 0.75 0.63 0.88 1.00 2.00 1.13 1.75 1.63 0.63
0.40 1.00 1.60 0.80 0.60 0.00 1.00 0.40 1.20 1.40
0.27 0.18 0.18 0.33 0.30 0.15 0.27 0.27 0.15 0.15
0.60 0.64 0.80 0.67 0.63 0.72 0.80 0.81 0.99 0.73
Table 8 Estimated efficiencies in liquid height reduction. Location
South East South South West Center East Center Center West North East North North West Outside (blank)
Efficiencies (mmhr 1) Morning
Afternoon
Night
Average
179.4 119.0 100.0 139.7 158.7 317.5 179.4 277.8 258.7 100.0
28.6 71.4 114.3 57.1 42.9 0.0 71.4 28.6 85.7 100.0
180.0 120.0 220.0 200.0 100.0 180.0 180.0 100.0 100.0 100.0
82.6 88.5 110.6 92.2 87.2 98.6 110.1 111.0 136.7 100.0
event, which produced a lowering in the evaporation of leachates and so far a smaller rate of liquid height reduction, during these events. Leachate inside the greenhouse with recharge on the 4, 9, 15 day exhibited a significant volume loss on the 4th and 15th day, while outside trays were not affected. Trays under stagnant condition exhibit a response similar to the one with recharge, it was observed that recharge has not an immediate effect onto liquid height reduction. It is noticeable that evaporation rate of the leachates outside the greenhouse was smaller than the rate observed inside. In addition, the process with recharge was more efficient than the stagnant one, a meaningful difference started to be noticeable after the 10th day, but it become significant after the 15th day, then it can be concluded that the action of recharging produce a positive impact. In Table 9 are reported values for the total height reduction registered on the 20th day, the daily rate of height reduction, and the estimated efficiency under the three types of processing (with recharge, stagnant and outside). Again, the 100% reference corresponds to the leachate left outside the greenhouse. During spring season, it happens that the internal microclimate of the greenhouse provided different response in respect to the ones observed during winter season. At winter, the maximum in both internal and external temperature occurred at 13:00 h, with average readings of 36.5 °C inside and 21 °C outside; otherwise during springtime, the major temperature raise took place during the morning and the maximum appeared after the 16:00 h, with average
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
Hydraulic liqquid depth reduction (mm)
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18.0 16.0 14.0 12.0 10.0 R
8.0
E
6.0
L
4.0 2.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Time, days Fig. 5. Leachate daily height reduction during test 3.
Table 9 Leachate height reduction for the 20 days experiment. Process
20 days height reduction (mm)
Daily rate (mmd 1)
Efficiency (%)
R E L
192.64 180.56 114.30
9.63 9.06 5.72
168.5 158.0 100.0
Table 10 Physicochemical leachate parameters. 1
ALK, mg L
Cl, mg L
1
[SO4], mg L
1
[PO4], mg L
1
Turbidity, NTU
[TS], mg L
EC, mS cm
1
1
pH
[COD], mg L
1
Day
0 (Raw)
5
10
15
20
L E R L E R L E R L E R L E R L E R L E R L E R L E R
9472 9472 9472 5334 5334 5334 10 10 10 51 51 51 875 875 875 19,260 19,260 19,260 9.15 9.15 9.15 8.10 8.10 8.10 7050 7050 7050
10,386 9547 9882 5598 5703 5915 190 120 120 23 23 10 1530 1330 1710 23,780 21,480 21,460 14.00 13.43 13.36 8.27 8.22 8.21 11,250 9150 10,200
9980 9283 9473 6844 6654 6337 200 230 250 16 9 12 1845 1740 1955 27,580 26,560 25,840 13.93 13.75 13.76 8.08 8.14 8.12 13,400 14,750 14,700
10,532 9585 11,333 6601 7816 6548 210 140 180 12 15 12 1965 2040 2310 27,800 29,000 28,600 13.37 13.64 13.77 8.13 8.24 8.17 13,350 11,550 14,650
10,285 9269 11,462 7288 9717 7974 250 120 110 21 41 24 2370 2450 2340 32,000 39,000 34,000 13.30 14.66 13.79 8.21 8.55 8.24 10,050 10,450 9750
values temperature values of 60 °C inside and 28 °C outside. The temperatures registered at the middle and top (liquid surface) exhibit a similar behavior to the ones observed during winter, but in spring temperature at the top exhibit
an almost null lowering, while during winter drops faster. The maximum value registered at the top (about 40 °C) took place after the 16:00 h for those trays located near the North wall; inside the greenhouse the other leachates reached a maximum temperature around midday and exhibit minimal variations in the following hours. Otherwise, leachates outside the greenhouse exhibit a similar behavior but they reached lower temperatures; for these trays it was observed that about the 16:00 h, temperature at middle height was higher than the one at the liquid surface, condition that was not observed in the internal trays. Chemical characterization was done for the raw leachate and samples collected at 5, 10, 15 and 20 days. Data are reported in Table 10. The follow up of the physical parameters indicates that pH is highly stable since changes are not greater than ±10% in respect to initial value. Physicochemical parameters in general show an increasing trend reaching up to two times the initial concentration in Total Solids (TS). At the 5th day the sample with higher increment in solids was the reference, while the ones inside have similar values, but at the 20th day higher value corresponds to the stagnant (E), followed by the recharged (R), and the outside (L) has the lower TS concentration. The phosphate (PO4) exhibit a lowering in concentration decreasing up to 17%, the minimal value was observed at 5th day for the R trays, E trays required 10 days, while the L ones required 15 days. Final concentration at 20 days indicates a recovery since R and L reached values close to 40% of their initial concentration, while the E ones reached 80%. Chemical Oxygen Demand (COD) and sulfates (SO4) exhibit similar trends an increase of concentration reaching its maximum between the 5th to 10th days, after that it occurs a decrease in concentration ending with similar values for all conditions in the case of the COD, for this parameter maximum concentration is less than 2.5 times the initial value. Otherwise the sulfates of R and E options follow similar trend reaching a maximum of 25 times initial concentration at 10 days, after that concentration decrease ending at a value of 10 times initial concentration. But the L option reached a maximum of 20 times its initial concen-
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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tration at the 5th day, remaining approximately stable up to the 15th day, and then steadily increase reaching 25 times original concentration at the 20th day. Chloride (Cl) is an anion showing a steadily increase in samples E and R, the E sample increased its concentration in 80%, the R increased in 50% and the L in 37%. It is noticeable that only the L sample showed an increase up to the 10th day, and at the 15th day exhibit a slight reduction, but for the 20th day concentration raised again. It is assumed that concentration variations are related to occurrence of chemical reactions, but due to the complexity in leachate chemical composition, it cannot be formulated any judgment about. 4. Conclusions About the structural design of the greenhouse it can be affirmed that the geomembrane played a roll of black body exerting a positive influence onto the liquid temperature at the bottom of the tray. The action of covering the North wall with aluminum foil allowed to induce an increment of liquid surface temperatures, and so far enhancing evaporation. The addition of windows for inducing ventilation was a key factor to enhance evaporation during afternoon and night; also it was observed that wind action can influence favorably the evaporation if the liquid surface reaches at least 20% of the tray height. At winter season, and during a 24 h period, using a greenhouse allowed to reach up to 47% more reduction in the liquid height, also it was observed that evaporation efficiencies are highly dependent on tray position inside the greenhouse During the 20 days experiment in spring time the use of the greenhouse have shown being more efficient in leachate reduction reaching efficiencies of 168% for the leachates under recharging conditions, and 158% for the ones left stagnant. The 100% reference corresponded to the ones left outside, which simulate a retention pond. Chemical characterization for TS, COD, and SO4 indicates that concentration increase in general but at different amount in respect to the initial concentration, TS reached 2 times, COD 2.5 times, SO4 25 times with minor variations in the E, R, or L trays. Chloride exhibit a different response since L increased in 37%, R in 50% and E in 80%. Opposite response was observed for PO4 since exhibit a decreasing trend ending with concentrations about 40% of the initial value. Finally, use of a greenhouse allow protecting leachates from environmental perturbations like dust. References Amor, C., De Torres-Socı´as, E., Pe´res, J.A., Maldonado, M.I., Oller, I., Malato, S., Lucas, M.S., 2015. Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photoFenton processes. J. Hazard. Mater. 286, 261–268.
Beyouncef, F., Makan, A., El Ghmari, A., Quatmane, A., 2016. Optimized evaporation technique for leachate treatment: small scale implementation. J. Environ. Manage. 170, 131–135. Cleber, R., Da Cruz Silva, K.C., Morita, D.M., Domı´ngues, J.A., Zaiat, M., Schalch, V., 2014. First order kinetics of landfill leachate treatment in a pilot –scale anaerobic sequence batch biofilm reactor. J. Environ. Manage. 145, 385–393. Contreras, J., Villarroel, M., Navia, R., Teutli, M., 2009. Treating landfill leachate by electrocoagulation. Waste Manage. Res. 27, 534–544. Garcı´a-Badell, J.J., 2003. Las leyes de la radiacio´n solar. En Ca´lculo de la energı´a solar. ISBN: 10 84-9527972-X. pp. 9–62. Hassan, M., Zhao, Y., Xie, B., 2016. Employing TiO2 photocatalysis to deal with a landfill leachate: Current status and development. Chem. Eng. J. 285, 264–275. He, R., Wei, X.-M., Tian, B.-H., Su, Y., Lu, Y.-L., 2015. Characterization of a joint recirculation of concentrated leachate and leachate to landfills with a microaerobic bioreactor for leachate treatment. Waste Manage. 46, 380–388. Hilles, A.H., Abu Amr, S.S., Hussein, R.M., El-Sebaie, O.D., Arafa, A.I., 2016. Performance of combined sodium persulfate/H2O2 based advanced oxidation process in stabilized landfill leachate treatment. J. Environ. Manage. 166, 493–498. Hu, L., Zeng, G., Chen, G., Dong, H., Liu, Y., Wan, J., Chen, A., Guo, Zh., Yan, M., Wu, H., Yu, Zh., 2016. Treatment of landfill leachate using immovilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles. J. Hazard. Mater. 301, 106–118. Huang, W., Wang, Zh., Guo, Q., Wang, H., Zhou, Y., Jern Ng, W., 2016. Pilot-scale landfill with leachate recirculation for enhanced stabilization. Biochem. Eng. J. 105, 437–445. Ismail, S., Tawfik, A., 2016. Performance of passive aereated immobilized biomass reactor coupled with Fenton process for treatment of landfill leachate. Int. Biodeterior. Biodegrad. 111, 22–30. Kumari, M., Ghosh, P., Thakur, I.Sh., 2016. Landfill leachate treatment using bacto-algal co-culture: An integrated approach using chemical analysis and toxicological assessment. Ecotoxicol. Environ. Saf. 128, 44–51. Liu, Zh., Wu, W., Shi, P., Guo, J., Cheng, J., 2015. Characterization of dissolved organic matter in landfill leachate during the combined treatment process of air stripping, Fenton, SBR and coagulation. Waste Manage. 41, 111–118. Mojiri, A., Ziyang, L., Tajuddin, R.M., Farraji, h., Alifar, N., 2016. Cotreatment of landfill leachate and municipal wastewater using the ZELIAC/zeolite constructed wetland system. J. Environ. Manage. 166, 124–130. Ogata, Y., Ishigaki, T., Ebie, Y., Sutthasil, N., Chiemchaisri, Ch., Yamada, M., 2015. Water reduction by constructed wetlands treating waste landfill leachate in a tropical region. Waste Manage. 44, 164– 171. Oulego, P., Collado, S., Laca, A., Dı´az, M., 2015. Tertiary treatment of biologically pre-treated landfill leachates by non-catalytic wet oxidation. Chem. Eng. J. 273, 647–655. Raghab, S.M., Abd El Meguid, A.M., Hegazi, H.A., 2013. Treatment of leachate from municipal solid waste landfill. HBRC J. 9, 187–192. Ramos, R., Aguilar, A., 2005. Modelacio´n del comportamiento de las isotermas, isoyectas y ca´lculo de la radiacio´n solar para el estado de Puebla durante el mes de junio de 2004. Elementos 58, 59–60. Sanguanpak, S., Chiemchaisri, Ch., Chiemchaisri, W., Yamamoto, K., 2015. Influence of operating pH on biodegradation performance and fouling propensity in membrane bioreactors for landfill leachate treatment. Int. Biodeterior. Biodegrad. 102, 64–72. Silva, T.F.C.V., Ferrera, R., Soares, P.A., Manenti, D.R., Fonseca, A., Saraiva, I., Boaventura, R.A.R., Vilar, V.J.P., 2015. Insights into solar photo-Fenton reaction parameters in the oxidation of a sanitary landfill leachate at lab-scale. J. Environ. Manage. 164, 32–40. Szanto´, M., Piraino, E., Arancibia, C.E. 2011. Criterios para el tratamiento de lixiviados de rellenos sanitarios mediante evaporacio´n por radiacio´n solar; en Hacia la sustentabilidad: Los residuos so´lidos
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Zhang, J., Gong, J.-L., Zenga, G.-M., Uo, X.-M., Jiang, Y., Chang, Y.N., Guo, M., Zhang, Chang, Liu, H.-L., 2016. Simultaneous removal of humic acid/fulvic acid and lead from landfill leachate using magnetic graphene oxide. Appl. Surf. Sci. 370, 335, 35. Zhou, B., Yu, Zh., Wei, Q., Long, H.Y., Xie, Y., Wang, Y., 2016. Electrochemical oxidation of biological pretreated and membrane separated landfill leachate concentrates on boron doped diamond anode. Appl. Surf. Sci. 377, 406–415.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
H O S T E D BY
Gulf Organisation for Research and Development
International Journal of Sustainable Built Environment ScienceDirect www.sciencedirect.com
Original Article/Research
Analysis of parameters for leachate treatment in a greenhouse system Ana Laura Go´mez Blasco a, Constantino Gutie´rrez b, Andre´s Armando Sa´nchez Herna´ndez c, Margarita Teutli Leo´n a,⇑ a
Facultad de Ingenierı´a, Beneme´rita Universidad Auto´noma de Puebla, Mexico b Universidad Nacional Auto´noma de Me´xico, Mexico c Facultad de Arquitectura, Beneme´rita Universidad Auto´noma de Puebla, Mexico Received 13 May 2016; accepted 8 February 2017
Abstract In this paper is presented an approach for landfill leachate treatment using enhanced natural evaporation. Experimental set up considered using a greenhouse pilot prototype placed into the municipal landfill of Puebla city, Me´xico. The greenhouse was built with a basement surface enough to place 9 trays with leachate. Treatment follow up was done through the following parameters: air temperature inside and outside the greenhouse; leachate temperature at surface and middle liquid height. Results of the first set of experiments defined a minimal initial liquid height of 20% in respect to the tray height; the 2nd set allowed defining optimal evaporation rate conditions evaluated in respect of a tray placed outside, considered as reference of 100% efficiency (blank), obtained results showed that morning and night processes provided efficiencies up to 2 times the reference; otherwise, afternoon measurements showed similar temperature values inside and outside. In general collected data at winter season provided efficiencies between 82% and 147%, in periods of 24 h, it was observed that higher liquid reductions took place at North, and lower ones at the South positions. Based on these results it was proposed a 20 days experiment, using stagnant (E) and recharge (R) conditions referred to the blank (L), the R process showed greater efficiency (168%) than the stagnant one (158%). Leachate chemical characterization indicates that pH is highly stable; while total solids, chemical oxygen demand, sulfate and chloride exhibit an increase in concentration reaching values of 1.2–2.5 times the initial concentration, phosphate was the only parameter exhibiting a decreasing trend ending with 40% of its initial concentration. Ó 2017 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.
Keywords: Landfill; Leachate; Evaporation; Greenhouse; Tray position
1. Introduction Actually urban solid wastes are disposed in landfills, where the inherent organic matter decomposition produce leachate liquids, and their amount is enhanced by liquids ⇑ Corresponding author.
E-mail address: [email protected] (M. Teutli Leo´n). Peer review under responsibility of The Gulf Organisation for Research and Development.
input into the confining cells; liquids come from external sources like runoff. Wrong actions in handling leachate liquid usually represent a contamination risk and a source of infections, therefore it is mandatory to implement actions to improve efficiency of applied treatment. There are reports about applied methods for leachate treatment, which at first approach operate under aerobic or anaerobic conditions (Cleber et al., 2014; Ismail and Tawfik, 2016), in treatment design facilities it has been con-
http://dx.doi.org/10.1016/j.ijsbe.2017.02.008 2212-6090/Ó 2017 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
sidered using natural systems like ponds and artificial wetlands (Ogata et al., 2015; Mojiri et al., 2016), while other systems accounted for leachate recirculation and evaporation (Huang et al., 2016; He et al., 2015). Research to improve leachate treatment has made use of membrane bioreactors, reverse osmosis, (Sanguanpak et al., 2015), electrocoagulation (Contreras et al., 2009), and flocculation (Raghab et al., 2013). Recent research approaches have explored applying Advance Oxidation Process (AOP) which involves generation of strong oxidants addressed to reduce the chemical oxygen demand (Silva et al., 2015; Hassan et al., 2016; Hilles et al., 2016; Zhou et al., 2016), also there are reports of treatments that use more than one technique (Amor et al., 2015; Wallace et al., 2015; Liu et al., 2015; Wu et al., 2015), some treatment options, based on unit operations, ranges from primary to tertiary treatment (Oulego et al., 2015; Kumari et al., 2016), while others have made incursion on nanotechnology (Hu et al., 2016; Zhang et al., 2016). From above mentioned reports it becomes evident that choosing a methodology for leachate treatment usually is a process defined by factors like: leachate chemical characteristics, site location, local weather, available land space for infrastructure, and the effluent final use, easiness in operation as well as inversion, operation and maintenance costs. There is a recent report of Beyouncef et al. (2016) in which they mention that evaporation (natural or forced) has not received the expected attention, especially in warm climate countries; they reported the design and implementation of a small scale forced evaporation tub and its comparison to a natural evaporation tub. They mention that key factors to accelerate leachate evaporation are the surface exposure to sunlight, stirring effect and aeration, but also they recognize that one of their minuses is the electric power consumption to operate both the agitator and aeration fan. Use of natural or induced evaporation should result in a reduction of leachate liquid volume, providing a sludge rich in salt and organic matter, which can either be returned to a final disposal cell or receive alternative treatment. Therefore, landfill operation should be favored since a concentrated sludge is easier to handle and it requires less space; so far, these actions imply an economical benefit. Research work reported in this paper was developed in Me´xico, for the Puebla city landfill, which is located at 2018 m above sea level, this is a site with an estimated area of 916,826.747 m2, whose UTM coordinates are between 590,578.4389-590,665.3343 East, and 2,098,706.79712,098,818.2245 North. Actual leachate production of 75 m3 per day is treated in 3 evaporative ponds (3000 m3 of installed capacity), 33% of treated leachate is recirculated to the active cells to provide humidity, and the rest (67%) are sent to a Waste Water Treatment Plant furnished with biological treatment for both sludge and liquid. Typical weather at Puebla is mild and semi humid, with an average of 5–40 mm daily precipitation during rainfall
season (from May to October), average temperatures range between 12 and 18 °C, with a minimum of 2 °C (at winter nights) and a maximum of 33 °C (at noon in spring). Also, official reports of wind patterns for Puebla city mention that there is presence of katabatic winds between 5 and 11 h running from North and North East to the South, these winds provide fresh and dry air; otherwise anabatic winds are present from 11 to sunset running from south to the north providing wet and warm air: additionally from sunset to sunrise there is presence of a light wind coming from the East. About solar intensity, there is a report (Ramos and Aguilar, 2005) which estimates that Puebla receives solar energy at the high atmosphere level with an estimated solar constant of 2 cal cm 2 min 1 obtained by correlating isotherms and isohyects data obtained in June 2004. Main goal in this project is to take advantage of weather conditions at Puebla to propose a leachate treatment at the landfill site, in which the leachate could be concentrated by enhanced evaporation. An experimental greenhouse was built at the landfill area with the purpose of evaluate how much leachate evaporation is increased by using a greenhouse installation. The first stage considered short time experiments to get enough data for defining optimal operating conditions, and the second stage was a long period experiment (20 days) to evaluate how the optimal conditions work for enhancing evaporation. 2. Materials and methods For designing and operating a greenhouse, the following external parameters should be accounted: amount of leachate to be treated, available space, site meteorological factors including latitude and altitude, solar radiation, temperature, relative humidity, presence of cloudiness, fog, evaporation, precipitation, as well as speed and direction of wind. These external factors will determine the greenhouse internal surface, roof slope and materials to be used; as well as optimal design to get the best conditions for internal climatic factors temperature, evaporation, humidity and ventilation. 2.1. Selection of materials for greenhouse construction Experimental greenhouse prototype construction should consider recommendations like the following ones: (a) walls and roof should be made of high transmittance materials (Szanto´ et al., 2011); (b) the slope of the roof should be designed according to the site latitude, since the maximum solar radiation intensity is captured with a perpendicular plane to the incident ray (Garcı´a-Badell, 2003); accounting for this recommendation the pilot greenhouse lower height wall was placed in the South position, and the higher at North, the last wall required been furnished with an aluminum cover, and the floor with a geomembrane which represents a black body, by which the bottom temperature in the greenhouse should be increased. Imple-
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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menting these recommendations allowed increasing the efficiency in capturing thermal energy from either albedo, walls or roof; (c) the greenhouse should be provided with a ventilation system, in order to assure that saturated air will be replaced by fresh air (Szanto´ et al., 2011), ventilation array should be such that air displacement takes place at a minimal ratio, so the greenhouse effect is barely constant during the whole day. It was observed that at Puebla landfill, it happens that both in-situ temperature and humidity dropped to low values, at afternoon hours, also the wind speed increases to significant values, therefore special measures were taken for assuring that at night the fresh air input into the greenhouse was enough for creating inner turbulences, which will compensate the heat loss due to air temperature drop. In Tables 1–3 is reported greenhouse technical information about construction materials, dimensions and implementation of the ventilation system. In Fig. 1 there is a picture of the pilot greenhouse set up at Puebla Landfill. Physical specifications of trays placed inside the greenhouse are reported in Table 4; and Fig. 2 is a picture of the experimental tray array inside the greenhouse. 2.2. Experimental design The methodology applied in this project consists in doing several experiments focused to discriminate if the greenhouse internal microclimate is adequate to provide the required evaporative conditions. Leachate evaporation was estimated by the average lowering in hydraulic liquid height at each tray, also leachate temperature was registered at two positions: one at the liquid surface and the other at a predefined height (134 mm from surface); also, it was accounted registering temperature inside and outside the greenhouse. It was estimated that the evaporation process should be sensitive to the hydraulic liquid depth in each tray; therefore the first set of experiments was run using 50, 100, 150, 200, 250, 300, 350, 400 and 415 mm of liquid height; placing trays in a parallel array, so far every tray was subject to the same climatic conditions. Since evaporative process could be favored in certain zones of the greenhouse; then other experiments were focused on finding a relationship between evaporation and tray position respect to the solar radiation incidence angle over the greenhouse basement. For this 2nd set of experiments all trays started with the same hydraulic liquid depth (350 mm); and a blank was a tray having the same Table 1 Greenhouse construction materials. Structure
Metallic tubes
Roof and walls Floor North wall (inside)
Transparent plastic 400 Geomembrane Aluminum sheet cover
3
Table 2 Pilot greenhouse dimensions. Base
180 cm 210 cm
Height 1 Height 2 Roof slope
150 cm 218 cm 19°
liquid height but placed outside the greenhouse, this tray simulated the process that could take place at a retention pond. Obtained average evaporation rates were analyzed by day period and tray position inside the greenhouse. Finally, another set of experiments (#3) were run considering a batch sequence in which the leachate was either stagnant (no-recharge) or recharged at fixed times; both conditions were tested simultaneously. For this experiment, 6 trays were used: 3 were left stagnant and the other 3 were recharged up to reach the initial hydraulic liquid height, this procedure took place each time that it was registered a 10% height loss. In this set the reference was a set of trays placed outside the greenhouse under the stagnant and recharge conditions. In this experiments, register of physical parameters included: temperature (T, °C); hydrogen potential (pH), electrical conductivity (EC, mS cm 1). And some physicochemical ones like: total solids (TS, mg L 1), chemical oxygen demand (COD, mg L 1), alkalinity (ALK, mg L 1), chloride (Cl, mg L 1), turbidity (NTU), phosphates (PO4, mg L 1), sulfates (SO4, mg L 1), and chemical oxygen demand (COD, mg L 1). The first and second experiments took place during winter season, while the third one occurred in spring season. In Table 5 are consigned the field experimental conditions. 3. Results and discussion 3.1. Determination of leachate optimal hydraulic liquid depth (Experiment 1) In Table 6 are reported average liquid height reduction. Trays exhibiting higher evaporation during daylight (Dtd) were the ones with initial height of 150, 300 y 415 mm. Otherwise, at night the trays with greater liquid height reduction (Dtn) were the ones with initial height of 100, 200, 250, 350 y 415 mm. When adding day and night (DtT) the observed reductions, it is observed that the tray with minor total evaporation was the one with lower initial hydraulic liquid height (50 mm); most of the trays with initial liquid height between 100 and 400 mm exhibit an average reduction of 6–7 mm per day. The tray with the maximum initial volume was the one of highest evaporation, reaching almost twice the evaporation obtained with the others; although only 9 mm was the difference in respect of the immediate previous one, therefore liquid height reduction cannot be direct consequence of the initial liquid height. It was expected that the tray with the lower liquid content would have the higher evaporation, but this tray was
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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Table 3 Greenhouse ventilation system. Period
Location
Night
Day
North South East West
South East
Up Up Down Up Down Up Center Center
Amount
Dimensions (cm)
Base percentage %
5 3 3 2 3 3 1 1
3 10 3 10 35 3 10 35 3 10 50 180 50 210
0.40 0.24 0.12 0.16 0.12 0.24 23.81 27.78
Trays with the higher evaporation rate were the ones starting with 150, 300 and 415 mm of liquid height, these trays were at the North position inside the greenhouse, therefore it can be concluded that tray location is important, as well as the enhancing factor exerted by light reflected at the aluminum covered wall at the North. 3.2. Liquid height reduction efficiency as a function of tray location inside the greenhouse (Experiment 2)
Fig. 1. Greenhouse pilot picture.
Table 4 Experimental trays dimensions. Width
36 cm
Large Height Material
56 cm 43 cm Transparent plastic
Fig. 2. Experimental tray array inside the greenhouse.
the one with the lower height reduction, fact that it is attributed to its position near the south wall, plus its low liquid height does not allowed being agitated by the night wind.
In this experiment all trays started with 350 mm of liquid height. As in experiment 1 data were collected at day and night, for better visualization it was proposed a color scale for representing registered hydraulic height measurements. It was chosen a red scale for daylight, grey scale for night and a blue scale for the total. In Fig. 3 are represented the assigned values for each color scale. This color scale has been applied in Fig. 4, where it is represented the liquid height reduction as function of tray position inside the greenhouse, array description in vertical direction goes South (base), Center, and North (aluminum wall), while in horizontal direction is described as West (left), Center and East (right), the reference is the tray outside the greenhouse (separate rectangle). As it can be observed during day time (red scale) the higher reductions are obtained at the North an especially at the West side; while at night (grey scale) higher values occur in the center and at the East side; combined observations (blue scale) show that height reduction exhibit an increasing trend from South to North. Taking into account the same distribution, in Table 7 are reported estimated average rates of liquid height reduction (mm-h 1) for each period of the day (morning, afternoon and night). In this Table it is evident that morning evaporation rates were higher for trays inside the greenhouse at the Center West and North positions, while that one placed at the South West showed an evaporation rate similar to the blank (0.63), but surprisingly at the afternoon this tray showed the higher rate (1.60), even slightly higher than the blank (1.40); otherwise the one at the Center West position is practically null (0.0). It is worthy to mention that at night only the Center West and the North East trays got rates similar to the blank, and all others overcome the one of the blank, which means that the implemented ventilation system works fine.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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Table 5 Experimental methodology. Test
Monitoring parameters
Monitoring frequency
Testing time
1. Optimal hydraulic liquid height determination 2. Liquid height reduction in function of its position inside the greenhouse 3. Stagnant versus recharge
Liquid height measurement Temperature at liquid surface Average liquid temperature, registered at 134 mm down from surface Greenhouse internal microclimate temperature Outside temperature at the experimental site T, pH, EC, TS, ALK, Cl, NTU, PO4, SO4 and COD
9:00, 13:00, 17:00, 20:00 h 9:30, 11:00, 12:30, 14:00, 15:30, 20:00 h 9:00, 13;00, 17:00 h
24 h 24 h
in the range of 82–111%. In general, 44% of the trays got efficiencies higher than 100% which is the blank value. About the leachate surface temperature, there is a direct relationship with tray position inside the greenhouse. Lower values belong to trays placed at the South; while those at the North not only were the ones having the highest values; but also these trays got the faster increments in temperature, reaching values above the average inner greenhouse temperature, this response is attributed to the closeness with the aluminum covered wall. Otherwise, leachate left outside the greenhouse exhibit a similar trend in temperature response to the ones inside, but global temperature raise was smaller. For this tray happened that at 13:00 h temperature taken at middle height was close to the one registered at the surface, also both temperatures were up to 10 °C higher than the air temperature. It is assumed that this higher leachate temperature contributed to increase the evaporation, in consequence this tray exhibited a liquid height reduction during afternoon period.
Table 6 Average liquid height reduction in experiment 1. Location
t0 (mm)
Dtd (mm)
Dtn (mm)
DtT (mm)
South East East North East South Center North South West West North West
50 100 150 200 250 300 350 400 415
4.0 2.0 5.0 2.0 3.0 5.0 3.0 4.0 7.0
0.0 5.0 1.0 4.0 4.0 2.0 4.0 2.0 8.0
4.0 7.0 6.0 6.0 7.0 7.0 7.0 6.0 15.0
t0: initial liquid height. Dtd: Average height reduction during daylight. Dtn: Average height reduction during night. DtT: Average height reduction per day.
It is remarkable that under the operating greenhouse conditions, the period with major contribution to the liquid height reduction was the morning one in which 89% of the trays got evaporations higher than the blank, at the afternoon results are really poor, and at night 78% of the trays got evaporation higher than the blank. Also results from all trays evidence that the North West position is the one having the greater evaporation during the morning; during the afternoon evaporation rates have not meaningful differences in respect to the blank tray placed outside; and during night time the greater evaporations were found at the Center East position. An average rate is reported at the last column by adding liquid height reductions observed in a 24 h period, these values indicate that 44% of leachate trays inside the greenhouse got greater evaporation than the blank outside. Efficiencies of liquid height reduction are shown in Table 8 these were estimated taking the blank as 100%. Attending to the average efficiency (last column), it is observed that higher evaporation correspond to trays placed at the North whose efficiency is between 110% and 137%, while the Center and South provide very close values ay (mm)
9.5
Night (mm)
5.5
Total (mm)
12.5
8.0 12.0
3.3. Comparison of stagnant versus recharged process (Experiment 3) For this step, it was considered a period of 20 days and experiments were run with recharging and stagnant conditions inside the greenhouse, and the blank outside. The recharge was done on the 4, 9 and 15 day. In Fig. 5 is presented the behavior profile of the liquid height reduction under the three process conditions, being R = average daily height reduction of internal trays with recharge; E = Average daily height reduction of stagnant internal trays; L = average height reduction of leachates outside the greenhouse. In general, for all days, leachate height reduction was greater inside the greenhouse than the one registered outside. On the 5th day, there was presence of condensation inside the structure. At the 10th day, it took place a rainfall 7.0
5.0
6.5 4.5
11.5
20 days
11.0
6.0
5.5
3.0 10.5
10.0
2.5 9.5
8.5
Fig. 3. Basic color scale for comparison of the liquid height reduction in trays.
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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Average leachate height reduction during day (mm)
Average leachate height reduction during night (mm)
(aluminum wall)
(aluminum wall)
Average leachate height reduction per day (mm) (aluminum wall)
Fig. 4. Average leachate height reduction per tray as function of its location inside the greenhouse.
Table 7 Leachate height reduction rates per periods of the day. Location
Height reduction rate (mmhr 1) Morning
Afternoon
Night
Average
South East South South West Center East Center Center West North East North North West Outside
1.13 0.75 0.63 0.88 1.00 2.00 1.13 1.75 1.63 0.63
0.40 1.00 1.60 0.80 0.60 0.00 1.00 0.40 1.20 1.40
0.27 0.18 0.18 0.33 0.30 0.15 0.27 0.27 0.15 0.15
0.60 0.64 0.80 0.67 0.63 0.72 0.80 0.81 0.99 0.73
Table 8 Estimated efficiencies in liquid height reduction. Location
South East South South West Center East Center Center West North East North North West Outside (blank)
Efficiencies (mmhr 1) Morning
Afternoon
Night
Average
179.4 119.0 100.0 139.7 158.7 317.5 179.4 277.8 258.7 100.0
28.6 71.4 114.3 57.1 42.9 0.0 71.4 28.6 85.7 100.0
180.0 120.0 220.0 200.0 100.0 180.0 180.0 100.0 100.0 100.0
82.6 88.5 110.6 92.2 87.2 98.6 110.1 111.0 136.7 100.0
event, which produced a lowering in the evaporation of leachates and so far a smaller rate of liquid height reduction, during these events. Leachate inside the greenhouse with recharge on the 4, 9, 15 day exhibited a significant volume loss on the 4th and 15th day, while outside trays were not affected. Trays under stagnant condition exhibit a response similar to the one with recharge, it was observed that recharge has not an immediate effect onto liquid height reduction. It is noticeable that evaporation rate of the leachates outside the greenhouse was smaller than the rate observed inside. In addition, the process with recharge was more efficient than the stagnant one, a meaningful difference started to be noticeable after the 10th day, but it become significant after the 15th day, then it can be concluded that the action of recharging produce a positive impact. In Table 9 are reported values for the total height reduction registered on the 20th day, the daily rate of height reduction, and the estimated efficiency under the three types of processing (with recharge, stagnant and outside). Again, the 100% reference corresponds to the leachate left outside the greenhouse. During spring season, it happens that the internal microclimate of the greenhouse provided different response in respect to the ones observed during winter season. At winter, the maximum in both internal and external temperature occurred at 13:00 h, with average readings of 36.5 °C inside and 21 °C outside; otherwise during springtime, the major temperature raise took place during the morning and the maximum appeared after the 16:00 h, with average
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
Hydraulic liqquid depth reduction (mm)
A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
7
18.0 16.0 14.0 12.0 10.0 R
8.0
E
6.0
L
4.0 2.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Time, days Fig. 5. Leachate daily height reduction during test 3.
Table 9 Leachate height reduction for the 20 days experiment. Process
20 days height reduction (mm)
Daily rate (mmd 1)
Efficiency (%)
R E L
192.64 180.56 114.30
9.63 9.06 5.72
168.5 158.0 100.0
Table 10 Physicochemical leachate parameters. 1
ALK, mg L
Cl, mg L
1
[SO4], mg L
1
[PO4], mg L
1
Turbidity, NTU
[TS], mg L
EC, mS cm
1
1
pH
[COD], mg L
1
Day
0 (Raw)
5
10
15
20
L E R L E R L E R L E R L E R L E R L E R L E R L E R
9472 9472 9472 5334 5334 5334 10 10 10 51 51 51 875 875 875 19,260 19,260 19,260 9.15 9.15 9.15 8.10 8.10 8.10 7050 7050 7050
10,386 9547 9882 5598 5703 5915 190 120 120 23 23 10 1530 1330 1710 23,780 21,480 21,460 14.00 13.43 13.36 8.27 8.22 8.21 11,250 9150 10,200
9980 9283 9473 6844 6654 6337 200 230 250 16 9 12 1845 1740 1955 27,580 26,560 25,840 13.93 13.75 13.76 8.08 8.14 8.12 13,400 14,750 14,700
10,532 9585 11,333 6601 7816 6548 210 140 180 12 15 12 1965 2040 2310 27,800 29,000 28,600 13.37 13.64 13.77 8.13 8.24 8.17 13,350 11,550 14,650
10,285 9269 11,462 7288 9717 7974 250 120 110 21 41 24 2370 2450 2340 32,000 39,000 34,000 13.30 14.66 13.79 8.21 8.55 8.24 10,050 10,450 9750
values temperature values of 60 °C inside and 28 °C outside. The temperatures registered at the middle and top (liquid surface) exhibit a similar behavior to the ones observed during winter, but in spring temperature at the top exhibit
an almost null lowering, while during winter drops faster. The maximum value registered at the top (about 40 °C) took place after the 16:00 h for those trays located near the North wall; inside the greenhouse the other leachates reached a maximum temperature around midday and exhibit minimal variations in the following hours. Otherwise, leachates outside the greenhouse exhibit a similar behavior but they reached lower temperatures; for these trays it was observed that about the 16:00 h, temperature at middle height was higher than the one at the liquid surface, condition that was not observed in the internal trays. Chemical characterization was done for the raw leachate and samples collected at 5, 10, 15 and 20 days. Data are reported in Table 10. The follow up of the physical parameters indicates that pH is highly stable since changes are not greater than ±10% in respect to initial value. Physicochemical parameters in general show an increasing trend reaching up to two times the initial concentration in Total Solids (TS). At the 5th day the sample with higher increment in solids was the reference, while the ones inside have similar values, but at the 20th day higher value corresponds to the stagnant (E), followed by the recharged (R), and the outside (L) has the lower TS concentration. The phosphate (PO4) exhibit a lowering in concentration decreasing up to 17%, the minimal value was observed at 5th day for the R trays, E trays required 10 days, while the L ones required 15 days. Final concentration at 20 days indicates a recovery since R and L reached values close to 40% of their initial concentration, while the E ones reached 80%. Chemical Oxygen Demand (COD) and sulfates (SO4) exhibit similar trends an increase of concentration reaching its maximum between the 5th to 10th days, after that it occurs a decrease in concentration ending with similar values for all conditions in the case of the COD, for this parameter maximum concentration is less than 2.5 times the initial value. Otherwise the sulfates of R and E options follow similar trend reaching a maximum of 25 times initial concentration at 10 days, after that concentration decrease ending at a value of 10 times initial concentration. But the L option reached a maximum of 20 times its initial concen-
Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008
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A.L. Go´mez Blasco et al. / International Journal of Sustainable Built Environment xxx (2017) xxx–xxx
tration at the 5th day, remaining approximately stable up to the 15th day, and then steadily increase reaching 25 times original concentration at the 20th day. Chloride (Cl) is an anion showing a steadily increase in samples E and R, the E sample increased its concentration in 80%, the R increased in 50% and the L in 37%. It is noticeable that only the L sample showed an increase up to the 10th day, and at the 15th day exhibit a slight reduction, but for the 20th day concentration raised again. It is assumed that concentration variations are related to occurrence of chemical reactions, but due to the complexity in leachate chemical composition, it cannot be formulated any judgment about. 4. Conclusions About the structural design of the greenhouse it can be affirmed that the geomembrane played a roll of black body exerting a positive influence onto the liquid temperature at the bottom of the tray. The action of covering the North wall with aluminum foil allowed to induce an increment of liquid surface temperatures, and so far enhancing evaporation. The addition of windows for inducing ventilation was a key factor to enhance evaporation during afternoon and night; also it was observed that wind action can influence favorably the evaporation if the liquid surface reaches at least 20% of the tray height. At winter season, and during a 24 h period, using a greenhouse allowed to reach up to 47% more reduction in the liquid height, also it was observed that evaporation efficiencies are highly dependent on tray position inside the greenhouse During the 20 days experiment in spring time the use of the greenhouse have shown being more efficient in leachate reduction reaching efficiencies of 168% for the leachates under recharging conditions, and 158% for the ones left stagnant. The 100% reference corresponded to the ones left outside, which simulate a retention pond. Chemical characterization for TS, COD, and SO4 indicates that concentration increase in general but at different amount in respect to the initial concentration, TS reached 2 times, COD 2.5 times, SO4 25 times with minor variations in the E, R, or L trays. Chloride exhibit a different response since L increased in 37%, R in 50% and E in 80%. Opposite response was observed for PO4 since exhibit a decreasing trend ending with concentrations about 40% of the initial value. Finally, use of a greenhouse allow protecting leachates from environmental perturbations like dust. References Amor, C., De Torres-Socı´as, E., Pe´res, J.A., Maldonado, M.I., Oller, I., Malato, S., Lucas, M.S., 2015. Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photoFenton processes. J. Hazard. Mater. 286, 261–268.
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Please cite this article in press as: Go´mez Blasco, A.L. et al. Analysis of parameters for leachate treatment in a greenhouse system. International Journal of Sustainable Built Environment (2017), http://dx.doi.org/10.1016/j.ijsbe.2017.02.008