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Acidic and alkaline bottom ash and composted manure blends as a soil amendment
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Bioresource Technology 99 (2008) 5891–5900
Acidic and alkaline bottom ash and composted manure blends as a soil amendment S. Mukhtar b
a,*
, S.S. Sadaka b, A.L. Kenimer a, S. Rahman a, J.G. Mathis
a
a Biological and Agricultural Engineering Department, Texas A&M University, Scoates Hall, College Station, TX 77843-2117, USA Department of Biological and Agricultural Engineering, University of Arkansas, 2301 S. University Avenue, Little Rock, AR 72204, USA
Received 29 March 2007; received in revised form 24 September 2007; accepted 24 September 2007 Available online 3 December 2007
Abstract Potential water quality impacts associated with using bottom ash (BA) and composted dairy manure (CM) as a soil amendment were evaluated in this study. Two column studies were conducted to evaluate three blends of acidic BA and CM (BA:CM, v/v) namely, B1ac (95:5), B2ac (90:10), and B3ac (80:20) and three blends of alkaline BA and CM (BA:CM, v/v), namely, B1al (95:5), B2al (90:10), and B3al (80:20) under constant head water table conditions. Samples from standing water (top) and leachate (bottom) were collected at weekly intervals until day 49 to evaluate the effects of different blend ratios and elapsed time on standing water and leachate chemical and physical properties. A higher CM content in both acidic and alkaline blends resulted in higher leachate concentrations for solids and nutrients tested in this study. Alkaline blends had higher standing water and leachate nutrients concentration compared to acidic blends. After day 28, standing water total dissolved solids (TDS) concentrations for all acidic blends was below the USEPA drinking water standard however, TDS value for alkaline blend was always below the standard. Similar trends were also observed for NO3–N and phosphorus (P) concentrations for both blends. Based on these findings, it was concluded that acidic and alkaline blends B1ac, B1al, B2ac and B2al may be considered as a soil amendment material. 2007 Elsevier Ltd. All rights reserved. Keywords: Bottom ash; Compost; Leachate; Manure; Nutrients
1. Introduction Bottom ash (BA), a course, granular, and incombustible material, is a by-product of coal combustion. It represents up to 20% of the total ash produced (Chen et al., 1991) from coal-fired power plants. Currently, less than one third of BA is recycled for road-base and sub-base aggregate, structural fill, and snow and ice control. Unused BA is typically retained at the power plant site. Ash management at coal-fired power plants is a costly problem and alternative uses need to be investigated. Bottom ash is predominantly an alkaline material with pH from 8.0 to 11.0. Acidic BA (pH of 6 or less), possibly caused by high sulfur (S) content
*
Corresponding author. Tel.: +1 979 458 1019; fax: +1 979 847 8828. E-mail address: [email protected] (S. Mukhtar).
0960-8524/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.09.089
(personal communications with utility plant personnel, Jewett, Texas) is less common. Studies suggest BA is high in nutrient values and has been used as a soil amendment (Adriano et al., 1980) without any adverse effects on soil and crop (Sell et al., 1989). The bulk of the manure from animal feeding operations (AFOs) in the USA is applied to crop and pastureland. Although manure is an excellent resource for plant nutrients and soil conditioning, excessive land application rate and improper uses of manure can lead to environmental concern. For example, Nitrate (NO3–N) is highly soluble and leads to groundwater contamination through nitrate leaching, while phosphorus (P) binds to soil particles and leads to surface water contamination with soil erosion. Composting is a popular process for manure handling. Composting is an aerobic process that allows microorganisms to decompose organic material. During this process
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heat, carbon dioxide (CO2), and water vapor are released into the atmosphere thus reducing the weight and mass of the material (Rynk, 1992). Manure that is excreted from dairy cattle contains 88% water and 12% solids (ASAE Standard, 2005). Composting reduces the moisture content to about 50% allowing for easier transportation (Miner et al., 2000). Compost is a valuable soil amendment that improves texture thus reducing the chances for erosion. Waste composting is popular because it reduces the risk of pollution and decreases odor complaints (Haug, 1993). Several prior studies have examined blended BA and composts and there is evidence that mixing of BA and composts could improve the quality of soil and increase plant growth. Butler and Bearce (1995) mixed BA with composted hardwood bark in proportions of 3:1, 2:1, and 1:1 (by volume) and BA with soil and peat in proportions of 1:1:1 (by volume) and studied their effects on Samantha rose bushes planted and cultured for a year. They observed that fresh weight of the rosebush stems grown in the ash and composted hardwood bark exceeded that of roses grown in the control medium (where soil, sand, and peat were mixed at a ratio of 1:1:1 by volume). Woodard et al. (1993) experimented with ‘Inca Yellow’ marigolds grown in BA and pinewood peelings, BA, pine wood peelings, and loose Grodan rockwool media. They found that marigolds grown in the BA and BA and pine wood peelings had a higher flower diameter than those grown in the other media. At the same time, BA and pinewood peelings blends showed higher K, Ca, and Mg concentrations than other blends. Limited research has been conducted on BA and alkaline composted dairy manure (CM) as a soil amendment. Mukhtar et al. (2003) investigated TKN, P, K, NO3–N, NH4–N, TS, VS, COD and trace metals under various blends of BA and CM as a soil amendment material at constant head and flow-through water conditions. It was found that higher CM content in the blend resulted in significantly higher leachate concentrations of these constituents. They recommended that further study is needed for BA and CM blends with reduced CM content (5, 10 and 20%) before using them as an environmentally safe soil amendment material. Therefore, a new study was designed to evaluate the feasibility of alternative blends of BA and CM under constant head water table management. In this study, it was assumed that under worst conditions such as a heavy rainfall event, un-compacted fill material (blends) with poor internal drainage of underlying soil might result in water ponding (standing water) above the saturated fill. In contrast, a quick de-saturation may occur following saturation due to high infiltration capacity of underlying soil. Under both situations, chemicals in the blends interacting with water may yield different water quality implications. Under highly wet conditions, these blends used as soil fill material may pose surface and groundwater pollution threat due to runoff from ponded water or leachate from saturated soil, respectively. The objective of this study was to evaluate water quality impacts associated with the
use of bottom ash (BA) and composted dairy manure (CM) as a soil amendment under saturated soil conditions. 2. Methods 2.1. Collection of materials Bottom ash (BA) was collected from ISG Resources Inc., a coal combustion by-product disposal company in Jewett, Texas. Mature dairy manure compost (CM) was collected from the composting facility located at the Texas A&M University System Animal Science Teaching Research and Extension Center near College Station, Texas. 2.2. Column preparation and experiment set-up Twelve 914 mm tall columns were constructed from 203 mm inside diameter acrylic pipe with a wall thickness of 6.4 mm. Three acidic blends of BA and CM: namely B1ac (95% BA:5% CM), B2ac (90% BA:10% CM), and B3ac (80% BA:20% CM) and three alkaline blends of BA and CM: namely, B1al (95% BA:5% CM), B2al (90% BA:10% CM), and B3al (80% BA:20% CM) were prepared on volume basis. In each column, a blend was placed in successive layers of approximately 2 L. All columns were packed to a height of 762 mm providing 152 mm headspace. Average bulk densities as result of blend packing are listed in Tables 2 and 3. A perforated acrylic plate was placed on top of the packed blend. Each treatment was randomly assigned to a column with four replicates. Thus, a total of 24 (3 · 4 · 2) columns were required for all acidic and alkaline blends. In between experiments, all columns were emptied and thoroughly cleaned with de-ionized water. De-ionized water was supplied from a carboy to each column until the water level reached 152 mm above the acrylic plate allowing for a constant head (no water leaving the column). Averages of 15.5, 15.8, and 16.5 L of de-ionized water were needed for the first saturation of acidic blends B1ac, B2ac, and B3ac, respectively. On an average 15.6, 16.4, and 17.3 L of de-ionized water were needed for the first saturation of alkaline blends B1al, B2al, and B3al, respectively. Once the water level inside each column reached the desired height, the water supply was stopped and the water supply tube from the carboy to the column was removed. This water table level was maintained for one week. At the end of the week, standing water above the medium was stirred very gently and one 160 ml sample per column was collected with a plastic disposable syringe. Subsequently, the bottom valve was opened to allow one 4 L leachate sample to be collected from each column. Fresh de-ionized water was then supplied to the columns until the water level returned to its previous level. The same procedure was repeated every week over a period of seven weeks. Detailed column preparation and experiment set-up description have been provided in Mukhtar et al. (2003).
S. Mukhtar et al. / Bioresource Technology 99 (2008) 5891–5900 Table 1 Analytical methods used on standing water and leachate samples Variables
Measuring methods
Reference
Total solids (TS)
Drying at 105 C
Total volatile solids (TVS) Total dissolved solids (TDS) Total suspended solids (TSS) pH
Combustion at 550 C Drying at 180 C
APHA Standard Methods (2005), Method #2540 B APHA Standard Methods (2005), Method #2540 E APHA Standard Methods (2005), Method #2540 C APHA Standard Methods (2005), Method #2540 D OMEGA Water Analyzer PHH-500 Series Digester Nelson and Sommers, (1973)
Total Kjeldahl nitrogen (TKN) Ammonium nitrogen Nitrate nitrogen P, K, Ca, Mg, Na, Zn, Fe, Cu, Mn
Filtration Probe Digest in sulfuric acid-hydrogen peroxide Spectronic 20D+ Spectronic 20D+ Elemental analyses by ICP
Hach (1997) Hach (1997) Angel and Feagley (1987)
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phosphorus (P), potassium (K) and metals in the Water Quality Laboratory (Biological and Agricultural Engineering Department) and Soil, Water and Forage Testing Laboratory (Soil and Crop Sciences Department) at Texas A&M University. Table 1 shows the analytical methods used throughout the study. 2.4. Statistical analysis A completely randomized design was used to compare blend effects and amount of water added over time to physicochemical properties of the leachate and standing water samples. The data were analyzed using ANOVA procedure on Stat View and SAS 9.1 software by SAS Inc. 3. Results and discussion 3.1. Properties of raw acidic and alkaline blends
2.3. Sample collection and analysis Samples were collected on day 7, 14, 21, 28, 35, and 49 after the constant head water table was established. Sampling events were pre-determined based on a previous study (Mukhtar et al., 2003) of CM and BA blends, where they found no significant changes in leachate and standing water constituents 49 days after initiating experiments. Standing water, leachate, and solid samples were analyzed for total solids (TS), total volatile solids (TVS), total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), pH, total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4–N), nitrate nitrogen (NO3–N), Table 2 Chemical and physical properties of acidic bottom ash (BA) and composted dairy manure (CM) (raw blends) and de-ionized water (volume basis) A
Variables
TKN P K Ca Mg Na Zn Fe Cu Mn pH Bulk density
BA:CM (95%:5%) (B1ac)
BA:CM (90%:10%) (B2ac)
BA:CM (80%:20%) (B3ac)
Deionized water
495B (±78)a NDC 2100 (±265)a 17,734 (±3478)a 698 (±84)a 2283 (±138)a 13.7 (±5.0)a 1005 (±1760)a 18.7 (±1.5)a 159 (±9.6)a 3.5 (±0.2) 1.1 (±0.1)a
932 (±82)b 300 (±0)a 2200 (±265)a 15,475 (±6752)a 891 (±28)b 1896 (±2220)b 12.7 (±0.6)a 725 (±208)b
1691 (±535)c 600 (±173)b 3000 (±458)b 17,458 (±63)a 1081 (±228)c 2145 (±132)a 21.3 (±7.6)b 681 (±136)b
3.8 (±4.1) ND 3.3 (±4.9) 18.8 (±29.9) ND 50 (±19) ND 0.8 (±0.8)
17.3 (±1.50)b 144 (±24.2)ab 3.5 (±0.1) 1.1 (±0.1)a
20.3 (±1.5)c 142 (±16.7)b 3.9 (±0.1) 1.0 (±0.1)b
ND ND 6.8 (±0.6) –
±Standard deviations, n = 3. A All variables in mg/L except bulk density (in Mg/m3) and pH. B Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 3. C ND = not detected.
Chemical properties of the raw acidic blends (prior to saturation) of BA and CM and de-ionized water are presented in Table 2. The data show that concentrations of TKN, P, K, and pH were higher for blends with higher CM content. Total Kjeldahl Nitrogen (TKN) and P concentrations for B3ac were significantly higher than those for B1ac and B2ac. The pH for these blends was very acidic. Table 3 Chemical and physical properties of alkaline bottom ash (BA) and composted dairy manure (CM) (raw blends) and de-ionized water (volume basis) VariablesA
BA:CM (95%:5%) (B1al)
BA:CM (90%:10%) (B2al)
BA:CM (80%:20%) (B3al)
Deionized water
TKN
207B (±95) a
677 (±343)b
906 (±251)c
P K
325 (±189)a 3200 (±337)a
425 (±126)ab 3425 (±206)a
500 (±116)b 3300 (±408)a
Ca Mg Na
27,355 (±2764)a 1140 (±361)a 1754 (±90)a
32,785 (±4785)b 1166 (±87)a 1927 (±44)a
31,495 (±4174)b 1127 (±106)a 1912 (±100)a
Zn
9 (±5.2)a
10.3 (±1.9)a
10.5 (±1.7)a
Fe
921 (±159)a
1011(±208)ab
1181 (±380)b
Cu
33.3 (±3.8)a
35.5 (±1.3)b
33.8 (±1.9)ab
Mn pHD(10.1)
243 (±27)a –
262 (±10)a –
246 (±29)a –
Bulk density
1.1 (±0.0)a
1.1 (±0.0)a
1.0 (±0.1)a
4.2 (±0.8) NDC 21.7 (±35) 10.1 (±9.3) ND 161 (±181) 0.1 (±0.2) 1.1 (±1.3) 0.1 (±0.2) ND 6.8 (±0.4) –
± Standard deviations, n = 3. A All variables in mg/L except bulk density (in Mg/m3) and pH. B Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 3. C ND = not detected. D pH is for 100% alkaline bottom ash only.
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In the following sections pH of standing water and leachate has been discussed separately, while other physiochemical constituents have been grouped and discussed as solids (i.e. TS, TVS, TDS, TSS), nutrients (i.e. TKN, NH4–N, NO3–N, P, K) and metals (i.e. Ca, Mg, Fe, Na). 3.2.1. pH Standing water and leachate pH for all acidic and alkaline blends are presented in Fig. 1. On day 7 (starting day) standing water pH values for B1ac, B2ac, and B3ac (Fig. 1a) were 4.3, 4.3, and 4.7, respectively, while leachate pH for B1ac, B2ac, and B3ac (Fig. 1c) were 3.4, 3.6, and 3.7, respectively. In both cases, initial conditions were very acidic. Initially (day 7), standing water pH for acidic blends was slightly higher than that of leachate due to the higher pH of added de-ionized water. Standing water pH for acidic blend, however, reduced to less than the leachate pH values for all blends at the end of the experiment (day 49). The leachate pH for all acidic blends increased slightly throughout the sampling period due to the addition of near neutral de-ionized water (pH 6.8). Leachate pH from B3ac remained higher than that for B1ac and B2ac throughout the experiment but they were not significantly different from one another. Standing water and leachate pH for alkaline blends were statistically similar (Fig. 1b and d). Standing water and leachate pH for all alkaline blends on day 7 was predominately neutral and increased slightly throughout the sampling events. Standing water pH for alkaline blends increased by 4.6, 4.5, and 4.3% for B1al, B2al, and B3al, respectively. This increase in pH over time
10
10
8
8
6
6
4 BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
2 0
0
7
14
21
28
35
42
4 BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
2 0
49
0
7
14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
10
10
8
8
6
6
pH (-)
pH (-)
3.2. Acidic and alkaline blend ratio effects on standing water and leachate characterization
pH (-)
pH (-)
Potassium concentration for B3ac was also significantly higher than that for the other two blends while K concentration for B2ac was higher but not statistically different from B1ac. For all acidic blends magnesium (Mg) and copper (Cu) concentrations increased with higher CM content of a blend. Concentrations for these two constituents were statistically different among all acidic blends. Iron (Fe) and manganese (Mn) concentrations decreased with increasing CM content and were significantly lower for B2ac and B3ac than B1ac. Trace amounts of TKN, K, calcium (Ca), sodium (Na), and iron (Fe) were detected in the near neutral (pH 6.8) de-ionized water indicating that the de-ionizing equipment likely had reached its treatment capacity. Chemical properties of alkaline BA and CM and de-ionized water prior to saturation are listed in Table 3. As with the acidic blends, TKN and P concentrations were higher for alkaline blends with a higher CM content. Total Kjeldahl Nitrogen concentration was significantly higher for B3al than those for B1al and B2al. For B3al, the P concentration was significantly higher than in B1al but statistically similar to B2al. Phosphorus concentration for B2al was higher than B1al but not significantly different. Potassium concentrations for all alkaline blends were similar. For all alkaline blends, Mg, Mn, sodium (Na) and zinc (Zn) concentrations were not statistically different. Calcium, Cu and Fe concentrations of B1al were significantly lower than those of B2al and B3al but B2al and B3al were not statistically different. De-ionized water was near neutral but trace amounts of TKN, K, Ca, Na, Zn, Fe, and Cu were detected. Additionally, it is evident from Table 2 that raw acidic blends had higher TKN and Zn and generally lower concentrations of all other variables as compared to the raw alkaline blends (Table 3).
4 BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
2
4 BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
2
0
49
0 0
7
14
21
28
35
Sampling event (days)
(c) Leachate, acidic blend
42
49
0
7
14
21
28
35
Sampling event (days)
(d) Leachate, alkaline blend
Fig. 1. Effects of acidic and alkaline BA:CM blends on standing water and leachate pH.
42
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was due to interaction of de-ionized water with alkaline BA and alkaline CM. Overall, blends with higher CM content showed a small increase in pH compared to blends with lower CM. 3.2.2. Solids Solids content of standing water and leachate from acidic (Table 4) and alkaline (Table 5) blends shows that average TS, TVS, TDS, and TSS concentrations in standing water were significantly lower than those in leachate. Also, average solids content of standing water and leachate for acidic blends was greater than their corresponding solids content in alkaline blends. In general, average TS, TVS, TDS, and TSS concentrations of standing water and leachate from among acidic blends or alkaline blends were statistically similar. However, these concentrations for standing water and leachate from alkaline blends increased with an increase in the CM content. As can be seen from Tables 4 and 5 that most of the solids content of standing
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water and leachate from all blends were in the form of dissolved solids (TDS), little or no TSS concentrations were observed among all blends. The effects of blend ratio and sampling event on standing water and leachate TS content for the acidic and alkaline blends are shown in Fig. 2. Standing water TS content for the three acidic blends (Fig. 2a) were significantly lower than that of leachate (Fig. 2c) because contact between the blend and water was greater for leachate than for standing water. At the end of the experiment, standing water TS content for B1ac, B2ac, and B3ac decreased by 69.8, 85.1, and 75.4%, respectively. As CM concentrations within blends increased so did the TS concentration in standing water. Standing water TS content for B3ac was significantly greater than that of B1ac and B2ac, while TS for the B1ac and B2ac were statistically similar (Fig. 2a). This statistical difference was due to gradual mixing of organic matter from the high CM blends with standing water. Over time this was also evident from the darker color of standing
Table 4 Standing water and leachate characteristics for acidic blends averaged over sampling events Variables
TS (g/L) TVS (g/L) TDS (g/L) TSS (g/L) NH4–N (mg/L) NO3–N (mg/L) Ca (mg/L) Mg (mg/L) Fe (mg/L) Na (mg/L)
Standing water
Leachate
BA:CM ratio (%)
BA:CM ratio (%)
95:5
90:10
80:20
95:5
90:10
80:20
B1ac
B2ac
B3ac
B1ac
B2ac
B3ac
0.45b ± 0.52 0.08b ± 0.20 0.48b ± 0.60 0.0c ± 0.0 0.30d ± 0.30 0.77b ± 0.41 80.7c ± 43.3 7.3b ± 16.7 5.6c ± 5.1 47.6c ± 29
1.12b ± 0.95 0.17b ± 0.27 0.88b ± 0.90 0.03c ± 0.08 1.43c ± 1.04 0.90b ± 0.55 139b ± 58.5 36.7b ± 44.2 14.1b ± 3.3 68.3c ± 43.7
13.4a ± 10.3 3.4a ± 2.0 13.3a ± 10.3 0.12b ± 0.08 4.9b ± 2.2 0.90b ± 0.43 526a ± 46.11 125a ± 79.3 215a ± 208 90b ± 38
12.3a ± 9.0 3.4a ± 2.4 12.2a ± 9 0.15b ± 0.08 11.8b ± 4.7 1.32b ± 0.60 526a ± 61.4 201a ± 132 241a ± 292 129ab ± 59.4
11.2a ± 5.9 2.7a ± 1.4 10.9a ± 6.1 0.30a ± 0.14 27.3a ± 9.6 2.4a ± 0.96 563a ± 115 326a ± 234a 293a ± 268 228a ± 131
A
0.40b ± 0.35 0.13b ± 0.16 0.38b ± 0.37 0.0c ± 0.0 0.13d ± 0.08 0.60b ± 0.37 53.6c ± 21.7 1.67b ± 4.1 5.3c ± 4.8 46.6c ± 21.5
±Standard deviation. A Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 6.
Table 5 Standing water and leachate characteristics for alkaline blends averaged over sampling events Variables
TS (g/L) TVS (g/L) TDS (g/L) TSS (g/L) NH4–N (mg/L) NO3–N (mg/L) Ca (mg/L) Mg (mg/L) Fe (mg/L) Na (mg/L)
Standing water
Leachate
BA:CM ratio (%)
BA:CM ratio
95:5
90:10
80:20
95:5
90:10
80:20
B1al
B2al
B3al
B1al
B2al
B3al
0.13b ± 0.08 0.08c ± 0.08 0.13b ± 0.08 0.0a ± 0.0 0.03c ± 0.08 0.70c ± 0.76 33.1b ± 9.3 1.7c ± 2.0 1.5b ± 1.1 202b ± 215
0.17b ± 0.05 0.07c ± 0.05 0.13b ± 0.05 0.0a ± 0.0 0.07c ± 0.12 0.65c ± 0.82 39.7b ± 10.5 4.6c ± 2.5 2.3b ± 1.5 201b ± 222
3.4a ± 1.4 0.60b ± 0.37 3.1a ± 1.8 0.02a ± 0.04 8.6b ± 6.4 1.6b ± 1.25 652a ± 58 79b ± 54.1 9.7a ± 5.9 276a ± 226
3.9a ± 2.3 0.97b ± 0.53 4 a ± 2.2 0.0a ± 0.0 19.1b ± 11.6 3.5b ± 1.25 638a ± 156 112b ± 66.1 4.8a ± 4.0 321a ± 261
5.5a ± 3.3 1.8a ± 0.83 5.3a ± 3.5 0.02a ± 0.04 43.5a ± 24.7 8.3a ± 4.8 641a ± 120 192a ± 73.4 5.7a ± 5.4 473a ± 330
A
0.17b ± 0.08 0.07c ± 0.08 0.17b ± 0.08 0.0a ± 0.0 0.07c ± 0.10 0.68c ± 0.73 37.6b ± 25.8 1.3c ± 3.1 1.2b ± 0.13 192b ± 217
±Standard deviation. A Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 6.
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3 2 1 0
3 2 1
0
7
14
21
28
35
42
0
49
0
7
14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
49
40
40 BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
30
TS (g/L)
30
TS (g/L)
BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
4
TS (g/L)
4
TS (g/L)
5
BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
20
20 10
10
0
0 0
7
14
21
28
35
42
49
Sampling event (days)
0
7
14
21
28
35
42
49
Sampling event (days)
(d) Leachate, alkaline blend
(c) Leachate, acidic blend Fig. 2. Effects of acidic and alkaline BA:CM blends on standing water and leachate TS.
water observed from blends with higher CM. Standing water TS for the three alkaline blends (Fig. 2b) was considerably lower than that for leachate from the three alkaline blends (Fig. 2d). Highest leachate TS concentration for acidic blend was observed on day 7 (first sampling event) for B1ac (32,500 mg/L), followed by B2ac (28,600 mg/L), and B3ac (21,500 mg/L). The largest decrease in TS concentration occurred between day 7 and day 14 for B1ac, B2ac and B3ac, by 46.5, 43.7, and 32.7%, respectively. From day 21 (third sampling event) until the experiment terminated (day 49), similar values of leachate TS concentration were observed for all blends. Compared to day 7, leachate TS for B1ac, B2ac and B3ac decreased by 84.7 80.5, and 69.3%, respectively, by the end of the experiment (day 49). On the other hand, following the first sampling event (day 7), the highest leachate TS values for alkaline blends were observed for B3al (11,130 mg/L), followed by B2al (7600 mg/L) and B1al (5700 mg/L). After the second sampling event (day 14), like that of acidic TS, a decrease in TS concentrations for these blends was observed. From the third sampling event (day 21) onwards, similar values of leachate TS were observed for all blends. At the end of the alkaline blend experiment, total volume flushed, leachate TS decreased by 81.0, 79.0, and 78.7% for B1al, B2al, and B3al, respectively. Although data not shown, similar trends were observed on the effects of blend ratio and sampling event on standing water and leachate TVS, TDS and TSS concentrations for all acidic and alkaline blends. One notable observation was that after day 14, standing water TDS concentrations were consistently below the USEPA drinking water standard of
500 mg/L for TDS of B1ac and B2ac (USEPA, 1994). Alkaline blend TDS for standing water was lower than the TDS for acidic blends. At the end of the experiment (day 49) concentrations of all solids in standing water and leachate of all blends reduced considerably. 3.2.3. Nutrients Standing water TKN for acidic blends decreased from day 7 to day 49 by 23.5, 45.8, and 17.6% for B1ac, B2ac, and B3ac, respectively, (Fig. 3a). Compared to day 7, standing water TKN for alkaline blends (Fig. 3b) decreased nearly 0.0, 15.0, and 31.8% for B1al, B2al, and B3al, respectively. Standing water and leachate TKN concentrations for alkaline blends were higher than those for acidic blends due to the higher pH (between 7 and 8) of standing water and leachate for all alkaline blends. Acidic blend B3ac had the highest amount of leachate TKN followed by blends B2ac and B1ac (Fig. 3c) indicating higher compost content in a blend yielded higher TKN in leachate. In addition, leachate TKN concentrations from all blends were significantly different. At the end of the experiment, leachate TKN for B1ac, B2ac, and B3ac decreased by 48.2, 48.1, and 48.5%, respectively, from their highest values. For all acidic blends, TKN for leachate was higher than standing water. This was due to lower concentrations of TDS and TVS in standing water than in leachate for all acidic blends. Due to the highest compost content, alkaline blend B3al had the highest leachate TKN concentration followed by B2al and B1al (Fig. 3d). At the same time, TKN concentrations for B1al, B2al, and B3al were significantly different. Generally, greater leachate TKN concentration was observed from alkaline
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Fig. 3. Effects of acidic and alkaline BA:CM blends on standing water and leachate TKN.
blends as compared to those for acidic blends. At the end of the experiment, leachate TKN decreased by 80.9, 82.8, and 87.3% for B1al, B2al, and B3al, respectively, from their highest values. Leachate TKN was significantly higher than standing water TKN for all alkaline blends since greater interaction between organic matter and the de-ionized water within the column allowed for higher leachate TKN. Average standing water and leachate NH4–N concentrations for acidic and alkaline blends are provided in Tables 4 and 5, respectively. For both blends, leachate resulted in significantly higher NH4–N concentration compare to standing water. Significant differences in standing water NH4–N concentrations were observed among acidic blends (Table 4), but not among alkaline blends (Table 5). For acidic blends, NH4–N concentration increased with increased CM content, but for alkaline no clear trend was observed. Ammonium nitrogen for alkaline blends was higher in leachate as compared to acidic blends. This was attributed to mineralization of organic nitrogen for alkaline blends (pH between 7 and 8) versus acidic blends (pH between 3.5 and 5.5). Standing water and leachate NO3–N for acidic (Table 4) and alkaline blends (Table 5) followed a trend similar to NH4–N for these blends. It is noteworthy that even at their highest concentrations, standing water and leachate NO3– N concentrations for all three acidic blends were below the USEPA drinking water standard of 10 mg/L for NO3–N (USEPA, 1994). Standing water NO3–N for all alkaline blends and leachate NO3–N for B1al and B2al was well below the USEPA drinking water standards during the entire experiment (Table 5). By day 28 (data not shown), leachate NO3–N concentration for all alkaline
blends was below the USEPA (1994) drinking water standard of 10 mg/L. Standing water P was not detected for any of the three acidic blends (Fig. 4a). Literature shows that lake eutrophication may occur with water P concentration above 0.02 mg/L (Sharpley, 1999). Since standing water P concentrations were nearly zero, use of these blends in environmental settings may not cause unacceptable P loadings into nearby water resources if water erosion is adequately controlled. Standing water P for alkaline blends was not detected in B1al and B2al (Fig. 4b). On day 49, a standing water P concentration 2.5 mg/L was measured for B3al. Only one of the 4 replicates for blend B3al generated a P concentration of 10 mg/L while no P was detected in the other three replicates, resulting in an average value of 2.5 mg/L. A low concentration of P in standing water is encouraging for the use of these blends in environmental settings. For all alkaline and acidic blends, standing water P was significantly lower than leachate. On day 7, the first sampling event, leachate P for acidic blends B1ac, B2ac, and B3ac was 5, 10, and 10 mg/L, respectively, (Fig. 4c). These values decreased nearly 100% for B1ac and B2ac on day 14 and B3ac on day 21. Blends B1ac and B3ac were statistically different from one another while B1ac and B2ac were statistically similar. Blends B2ac and B3ac were also statistically similar. The mean values for leachate P for B2ac and B3ac were higher than B1ac due to the higher CM content. Alkaline blends B1al and B2al were statistically similar while B1al and B3al, and B2al and B3al were significantly different from each other. Leachate P for B1al was not detected during the duration of the experiment (Fig. 4d). Leachate B2al decreased
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Fig. 4. Effects of acidic and alkaline BA:CM blends on standing water and leachate P.
66.7% while B3al increased 1.4%. Like the acidic blends, leachate P for alkaline blend B3al was higher than those of B1al and B2al due to the higher CM concentration in B3al. Leachate P for alkaline blends was higher than acidic blends due to higher P content of raw, unsaturated alkaline blends (especially, B1al and B2al) and due to high pH for alkaline blends versus acidic blends.
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As can be seen from Fig. 5a that for acidic blends, standing water K was the highest for B1ac and B2ac on day 7 and decreased by 52.0 and 89.7%, respectively, by the end of the sampling events. Leachate K for acidic blend (Fig. 5c) was highest for B1ac, B2ac, and B3ac on day 7 (first sampling event). Leachate K concentration for acidic blend B3ac was significantly higher than B1ac and B2ac due to the
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higher CM content of this blend. By the end of the experiment, leachate K for B1ac, B2ac, and B3ac decreased by 81.5, 80.5, and 79.5%, respectively. The highest leachate K for alkaline blends was also observed on day 7 for B1al, B2al, and B3al (Fig. 5d). By the end of the experiment, leachate K for B1al, B2al, and B3al decreased 90.5, 90.8, and 90.2%, respectively. For all acidic and alkaline blends, leachate K was significantly higher than that of standing water due to greater interaction between organic matter and the de-ionized water within the column. Standing water K for alkaline blends was the highest on day 14 and by the end of the experiment (day 49) decreased by 74.1, 35.5, and 57.0% for B1al, B2al and B3al, respectively, (Fig. 5b). Leachate K for B3al was higher than B1al and B2al. All alkaline blends were significantly different from one another. A similar trend was seen in the acidic blends. Standing water and leachate K for alkaline blends was higher than acidic blends due to higher K content of raw blends and due to high pH for alkaline blends versus acidic blends (Tables 2 and 3). 3.2.4. Metals Average concentrations of standing water and leachate Ca, Mg, Fe, and Na are shown in Tables 4 and 5 for acidic and alkaline blends, respectively. Concentrations of these elements in standing water were significantly lower than that in leachate. Increasing time resulted in decreasing concentrations of all the elements, except Ca concentration in acidic blends (data not shown). With the exception of Na, standing water and leachate concentrations of Ca, Mg, and Fe were generally greater in acidic blends compared to alkaline blends (Tables 4 and 5). This occurred even though raw acidic blends (Table 2) had lower concentrations of these elements than raw alkaline blends (Table 3). This may be the result of increased leaching and availability of these traces metals due to very low pH (between 3.5 and 5.5) for acidic blends of BA and CM. Meima and Comans (1999) observed reduced leaching of these and other trace elements due to reduced solubility of these elements as a result of near neutral pH of BA. Therefore, possibility of greater leaching and availability of trace metals from low pH blends of BA and CM must be considered before using them as a soil amendment. Additionally, decreased soil pH as a result of these acidic amendments may depress the growth of some plant species such as maize, wheat, tomato and zinger (Islam et al., 1980). 4. Summary and conclusions Three acidic blends of bottom ash and composted dairy manure (BA: CM%, v/v) namely: B1ac (95:5%), B2ac (90:10%), and B3ac (80:20%) and three alkaline blends namely: B1al (95:5%), B2al (90:10%), and B3al (80:20%) were evaluated for potential use as a soil amendment material. The blends were subjected to constant head water table management using de-ionized water. Based on the findings of this study it was concluded that the amount
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of CM in acidic and alkaline blends impacted the concentrations of most of the physicochemical parameters tested in raw blends, leachate, and standing water. Concentrations of nearly all chemicals were lower in standing water (top) compared to leachate (bottom) for acidic and alkaline blends. For both acidic and alkaline blends, concentrations of almost all constituents were greatest for the first samples (day 7) of leachate and standing water but reduced significantly at the end of this study (day 49). Standing water and leachate concentrations of all solids for alkaline blends were lower than those for the acidic blends. Standing water and leachate TKN, NH4–N and NO3–N concentrations for alkaline blends were higher than those for acidic blends due to higher pH (between 7 and 8) of standing water and leachate for all alkaline blends. Standing water and leachate NO3–N concentrations for all acidic blends and for alkaline blends B1al and B2al were below the USEPA drinking water standard for nitrate. Phosphorus concentrations were low in leachate and nonexistent in standing water for acidic and alkaline blends. In light of these findings it is suggested that acidic and alkaline blends B1ac, B1al, B2ac and B2al may be considered as a soil amendment substitute. However, reduced pH of acidic blend amended soil may depress the growth of plant species that are susceptible to low pH. Under saturated conditions, acidic blend amended soils may also release greater concentrations of trace metals to the environment as compared to alkaline blend amended soils. Acknowledgements The authors would like to thank the team of the ISG, Resources Inc. Jewett, Texas for their corporation and supply of bottom ash used in this study. These studies were conducted in laboratories of the Department of Biological and Agricultural Engineering at the Texas A&M University, College Station, Texas. References Adriano, D.C., Page, A.L., Elseewi, A.L., Chang, A.C., Straughan, I., 1980. Utilization and disposal of fly ash and other coal residues in terrestrial ecosystems. Journal of Environmental Quality 9, 333–344. Angel, C.E., Feagley, S.E., 1987. The effect of lime and fertilizer on four lignite overburdens under non-drained conditions: 1. Yield and nutrient concentration of common bermudagrass. Communication in Soil Science and Plant Analysis 18, 963–980. APHA, 2005. Standard Methods for Examination of Water and Wastewater, 21st ed. American Public Health Association, New York. ASAE Standards, 2005. D384.2, Manure Production and Characteristics. American Society of Agricultural Engineers, St. Joseph, Michigan. Butler, S.H., Bearce, B.C., 1995. Greenhouse rose production in media containing coal bottom ash. Journal of Environmental Horticulture 13, 160–164. Chen, Y., Gottesman, A., Aviad, T., Inbar, Y., 1991. The use of bottomash coal-cinder amended with compost as a container medium in horticulture. International Society for Horticultural Science 294, 173– 181. Hach, 1997. Water Analysis Handbook, third ed. Hach Company, Loveland, Colorado, USA.
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Haug, R.T., 1993. The Practical Handbook of Compost Engineering. Lewis Publishers, Boca Raton, Florida. Islam, A.K.M.S., Edwards, D.G., Asher, C.J., 1980. pH optima for crop growth results of a flowing solution culture experiment with six species. Plant and Soil 54, 339–357. Meima, J.A.R., Comans, N.J., 1999. The leaching of trace elements from municipal solid waste incinerator bottom ash at different stages of weathering. Applied Geochemistry 14, 159–171. Miner, J.R., Humenik, F.J., Overcash, M.R., 2000. Managing livestock waste to preserve environmental quality. Iowa State University Press, Ames, Iowa. Mukhtar, S., Kenimer, A.L., Sadaka, S.S., Mathis, J.G., 2003. Evaluation of bottom ash and composted dairy manure as a soil amendment material. Bioresource Technology 89, 217–228. Nelson, D.W., Sommers, L.E., 1973. Determination of total nitrogen in plant material. Agronomy Journal 65, 109–112.
Rynk, R., 1992. On-Farm Composting Handbook. Northeast Regional Agricultural Engineering Service. Publication Number: NRAES-54, Ithaca, New York. Sell, N., McIntosh, T., Severance, C., Peterson, A., 1989. The agronomic land spreading of coal BA: using a regulated solid waste as a resource. Resources, Conservation and Recycling 2, 119–129. Sharpley, A.N., 1999. Agricultural phosphorus and eutrophication. Agricultural Research Service. Publication No. ARS-149.1999. TFHRC. Turner-Fairbank Highway Research Center website, http:// www.tfhrc.gov/hnr20/recycle/waste/cbabs1, (accessed on January 2005). USEPA, 1994. Water Quality Standards Handbook, second ed. Update 1. Order Number: EPA/823-B-94-006. Woodard, M.A., Bearce, B., Cluskey, C., Townsend, S.E.C., 1993. Coal bottom ash and pine wood peelings as root substrates in a circulating nutriculture system. Horticultural Science 28, 636–638.
Bioresource Technology 99 (2008) 5891–5900
Acidic and alkaline bottom ash and composted manure blends as a soil amendment S. Mukhtar b
a,*
, S.S. Sadaka b, A.L. Kenimer a, S. Rahman a, J.G. Mathis
a
a Biological and Agricultural Engineering Department, Texas A&M University, Scoates Hall, College Station, TX 77843-2117, USA Department of Biological and Agricultural Engineering, University of Arkansas, 2301 S. University Avenue, Little Rock, AR 72204, USA
Received 29 March 2007; received in revised form 24 September 2007; accepted 24 September 2007 Available online 3 December 2007
Abstract Potential water quality impacts associated with using bottom ash (BA) and composted dairy manure (CM) as a soil amendment were evaluated in this study. Two column studies were conducted to evaluate three blends of acidic BA and CM (BA:CM, v/v) namely, B1ac (95:5), B2ac (90:10), and B3ac (80:20) and three blends of alkaline BA and CM (BA:CM, v/v), namely, B1al (95:5), B2al (90:10), and B3al (80:20) under constant head water table conditions. Samples from standing water (top) and leachate (bottom) were collected at weekly intervals until day 49 to evaluate the effects of different blend ratios and elapsed time on standing water and leachate chemical and physical properties. A higher CM content in both acidic and alkaline blends resulted in higher leachate concentrations for solids and nutrients tested in this study. Alkaline blends had higher standing water and leachate nutrients concentration compared to acidic blends. After day 28, standing water total dissolved solids (TDS) concentrations for all acidic blends was below the USEPA drinking water standard however, TDS value for alkaline blend was always below the standard. Similar trends were also observed for NO3–N and phosphorus (P) concentrations for both blends. Based on these findings, it was concluded that acidic and alkaline blends B1ac, B1al, B2ac and B2al may be considered as a soil amendment material. 2007 Elsevier Ltd. All rights reserved. Keywords: Bottom ash; Compost; Leachate; Manure; Nutrients
1. Introduction Bottom ash (BA), a course, granular, and incombustible material, is a by-product of coal combustion. It represents up to 20% of the total ash produced (Chen et al., 1991) from coal-fired power plants. Currently, less than one third of BA is recycled for road-base and sub-base aggregate, structural fill, and snow and ice control. Unused BA is typically retained at the power plant site. Ash management at coal-fired power plants is a costly problem and alternative uses need to be investigated. Bottom ash is predominantly an alkaline material with pH from 8.0 to 11.0. Acidic BA (pH of 6 or less), possibly caused by high sulfur (S) content
*
Corresponding author. Tel.: +1 979 458 1019; fax: +1 979 847 8828. E-mail address: [email protected] (S. Mukhtar).
0960-8524/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.09.089
(personal communications with utility plant personnel, Jewett, Texas) is less common. Studies suggest BA is high in nutrient values and has been used as a soil amendment (Adriano et al., 1980) without any adverse effects on soil and crop (Sell et al., 1989). The bulk of the manure from animal feeding operations (AFOs) in the USA is applied to crop and pastureland. Although manure is an excellent resource for plant nutrients and soil conditioning, excessive land application rate and improper uses of manure can lead to environmental concern. For example, Nitrate (NO3–N) is highly soluble and leads to groundwater contamination through nitrate leaching, while phosphorus (P) binds to soil particles and leads to surface water contamination with soil erosion. Composting is a popular process for manure handling. Composting is an aerobic process that allows microorganisms to decompose organic material. During this process
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heat, carbon dioxide (CO2), and water vapor are released into the atmosphere thus reducing the weight and mass of the material (Rynk, 1992). Manure that is excreted from dairy cattle contains 88% water and 12% solids (ASAE Standard, 2005). Composting reduces the moisture content to about 50% allowing for easier transportation (Miner et al., 2000). Compost is a valuable soil amendment that improves texture thus reducing the chances for erosion. Waste composting is popular because it reduces the risk of pollution and decreases odor complaints (Haug, 1993). Several prior studies have examined blended BA and composts and there is evidence that mixing of BA and composts could improve the quality of soil and increase plant growth. Butler and Bearce (1995) mixed BA with composted hardwood bark in proportions of 3:1, 2:1, and 1:1 (by volume) and BA with soil and peat in proportions of 1:1:1 (by volume) and studied their effects on Samantha rose bushes planted and cultured for a year. They observed that fresh weight of the rosebush stems grown in the ash and composted hardwood bark exceeded that of roses grown in the control medium (where soil, sand, and peat were mixed at a ratio of 1:1:1 by volume). Woodard et al. (1993) experimented with ‘Inca Yellow’ marigolds grown in BA and pinewood peelings, BA, pine wood peelings, and loose Grodan rockwool media. They found that marigolds grown in the BA and BA and pine wood peelings had a higher flower diameter than those grown in the other media. At the same time, BA and pinewood peelings blends showed higher K, Ca, and Mg concentrations than other blends. Limited research has been conducted on BA and alkaline composted dairy manure (CM) as a soil amendment. Mukhtar et al. (2003) investigated TKN, P, K, NO3–N, NH4–N, TS, VS, COD and trace metals under various blends of BA and CM as a soil amendment material at constant head and flow-through water conditions. It was found that higher CM content in the blend resulted in significantly higher leachate concentrations of these constituents. They recommended that further study is needed for BA and CM blends with reduced CM content (5, 10 and 20%) before using them as an environmentally safe soil amendment material. Therefore, a new study was designed to evaluate the feasibility of alternative blends of BA and CM under constant head water table management. In this study, it was assumed that under worst conditions such as a heavy rainfall event, un-compacted fill material (blends) with poor internal drainage of underlying soil might result in water ponding (standing water) above the saturated fill. In contrast, a quick de-saturation may occur following saturation due to high infiltration capacity of underlying soil. Under both situations, chemicals in the blends interacting with water may yield different water quality implications. Under highly wet conditions, these blends used as soil fill material may pose surface and groundwater pollution threat due to runoff from ponded water or leachate from saturated soil, respectively. The objective of this study was to evaluate water quality impacts associated with the
use of bottom ash (BA) and composted dairy manure (CM) as a soil amendment under saturated soil conditions. 2. Methods 2.1. Collection of materials Bottom ash (BA) was collected from ISG Resources Inc., a coal combustion by-product disposal company in Jewett, Texas. Mature dairy manure compost (CM) was collected from the composting facility located at the Texas A&M University System Animal Science Teaching Research and Extension Center near College Station, Texas. 2.2. Column preparation and experiment set-up Twelve 914 mm tall columns were constructed from 203 mm inside diameter acrylic pipe with a wall thickness of 6.4 mm. Three acidic blends of BA and CM: namely B1ac (95% BA:5% CM), B2ac (90% BA:10% CM), and B3ac (80% BA:20% CM) and three alkaline blends of BA and CM: namely, B1al (95% BA:5% CM), B2al (90% BA:10% CM), and B3al (80% BA:20% CM) were prepared on volume basis. In each column, a blend was placed in successive layers of approximately 2 L. All columns were packed to a height of 762 mm providing 152 mm headspace. Average bulk densities as result of blend packing are listed in Tables 2 and 3. A perforated acrylic plate was placed on top of the packed blend. Each treatment was randomly assigned to a column with four replicates. Thus, a total of 24 (3 · 4 · 2) columns were required for all acidic and alkaline blends. In between experiments, all columns were emptied and thoroughly cleaned with de-ionized water. De-ionized water was supplied from a carboy to each column until the water level reached 152 mm above the acrylic plate allowing for a constant head (no water leaving the column). Averages of 15.5, 15.8, and 16.5 L of de-ionized water were needed for the first saturation of acidic blends B1ac, B2ac, and B3ac, respectively. On an average 15.6, 16.4, and 17.3 L of de-ionized water were needed for the first saturation of alkaline blends B1al, B2al, and B3al, respectively. Once the water level inside each column reached the desired height, the water supply was stopped and the water supply tube from the carboy to the column was removed. This water table level was maintained for one week. At the end of the week, standing water above the medium was stirred very gently and one 160 ml sample per column was collected with a plastic disposable syringe. Subsequently, the bottom valve was opened to allow one 4 L leachate sample to be collected from each column. Fresh de-ionized water was then supplied to the columns until the water level returned to its previous level. The same procedure was repeated every week over a period of seven weeks. Detailed column preparation and experiment set-up description have been provided in Mukhtar et al. (2003).
S. Mukhtar et al. / Bioresource Technology 99 (2008) 5891–5900 Table 1 Analytical methods used on standing water and leachate samples Variables
Measuring methods
Reference
Total solids (TS)
Drying at 105 C
Total volatile solids (TVS) Total dissolved solids (TDS) Total suspended solids (TSS) pH
Combustion at 550 C Drying at 180 C
APHA Standard Methods (2005), Method #2540 B APHA Standard Methods (2005), Method #2540 E APHA Standard Methods (2005), Method #2540 C APHA Standard Methods (2005), Method #2540 D OMEGA Water Analyzer PHH-500 Series Digester Nelson and Sommers, (1973)
Total Kjeldahl nitrogen (TKN) Ammonium nitrogen Nitrate nitrogen P, K, Ca, Mg, Na, Zn, Fe, Cu, Mn
Filtration Probe Digest in sulfuric acid-hydrogen peroxide Spectronic 20D+ Spectronic 20D+ Elemental analyses by ICP
Hach (1997) Hach (1997) Angel and Feagley (1987)
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phosphorus (P), potassium (K) and metals in the Water Quality Laboratory (Biological and Agricultural Engineering Department) and Soil, Water and Forage Testing Laboratory (Soil and Crop Sciences Department) at Texas A&M University. Table 1 shows the analytical methods used throughout the study. 2.4. Statistical analysis A completely randomized design was used to compare blend effects and amount of water added over time to physicochemical properties of the leachate and standing water samples. The data were analyzed using ANOVA procedure on Stat View and SAS 9.1 software by SAS Inc. 3. Results and discussion 3.1. Properties of raw acidic and alkaline blends
2.3. Sample collection and analysis Samples were collected on day 7, 14, 21, 28, 35, and 49 after the constant head water table was established. Sampling events were pre-determined based on a previous study (Mukhtar et al., 2003) of CM and BA blends, where they found no significant changes in leachate and standing water constituents 49 days after initiating experiments. Standing water, leachate, and solid samples were analyzed for total solids (TS), total volatile solids (TVS), total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), pH, total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4–N), nitrate nitrogen (NO3–N), Table 2 Chemical and physical properties of acidic bottom ash (BA) and composted dairy manure (CM) (raw blends) and de-ionized water (volume basis) A
Variables
TKN P K Ca Mg Na Zn Fe Cu Mn pH Bulk density
BA:CM (95%:5%) (B1ac)
BA:CM (90%:10%) (B2ac)
BA:CM (80%:20%) (B3ac)
Deionized water
495B (±78)a NDC 2100 (±265)a 17,734 (±3478)a 698 (±84)a 2283 (±138)a 13.7 (±5.0)a 1005 (±1760)a 18.7 (±1.5)a 159 (±9.6)a 3.5 (±0.2) 1.1 (±0.1)a
932 (±82)b 300 (±0)a 2200 (±265)a 15,475 (±6752)a 891 (±28)b 1896 (±2220)b 12.7 (±0.6)a 725 (±208)b
1691 (±535)c 600 (±173)b 3000 (±458)b 17,458 (±63)a 1081 (±228)c 2145 (±132)a 21.3 (±7.6)b 681 (±136)b
3.8 (±4.1) ND 3.3 (±4.9) 18.8 (±29.9) ND 50 (±19) ND 0.8 (±0.8)
17.3 (±1.50)b 144 (±24.2)ab 3.5 (±0.1) 1.1 (±0.1)a
20.3 (±1.5)c 142 (±16.7)b 3.9 (±0.1) 1.0 (±0.1)b
ND ND 6.8 (±0.6) –
±Standard deviations, n = 3. A All variables in mg/L except bulk density (in Mg/m3) and pH. B Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 3. C ND = not detected.
Chemical properties of the raw acidic blends (prior to saturation) of BA and CM and de-ionized water are presented in Table 2. The data show that concentrations of TKN, P, K, and pH were higher for blends with higher CM content. Total Kjeldahl Nitrogen (TKN) and P concentrations for B3ac were significantly higher than those for B1ac and B2ac. The pH for these blends was very acidic. Table 3 Chemical and physical properties of alkaline bottom ash (BA) and composted dairy manure (CM) (raw blends) and de-ionized water (volume basis) VariablesA
BA:CM (95%:5%) (B1al)
BA:CM (90%:10%) (B2al)
BA:CM (80%:20%) (B3al)
Deionized water
TKN
207B (±95) a
677 (±343)b
906 (±251)c
P K
325 (±189)a 3200 (±337)a
425 (±126)ab 3425 (±206)a
500 (±116)b 3300 (±408)a
Ca Mg Na
27,355 (±2764)a 1140 (±361)a 1754 (±90)a
32,785 (±4785)b 1166 (±87)a 1927 (±44)a
31,495 (±4174)b 1127 (±106)a 1912 (±100)a
Zn
9 (±5.2)a
10.3 (±1.9)a
10.5 (±1.7)a
Fe
921 (±159)a
1011(±208)ab
1181 (±380)b
Cu
33.3 (±3.8)a
35.5 (±1.3)b
33.8 (±1.9)ab
Mn pHD(10.1)
243 (±27)a –
262 (±10)a –
246 (±29)a –
Bulk density
1.1 (±0.0)a
1.1 (±0.0)a
1.0 (±0.1)a
4.2 (±0.8) NDC 21.7 (±35) 10.1 (±9.3) ND 161 (±181) 0.1 (±0.2) 1.1 (±1.3) 0.1 (±0.2) ND 6.8 (±0.4) –
± Standard deviations, n = 3. A All variables in mg/L except bulk density (in Mg/m3) and pH. B Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 3. C ND = not detected. D pH is for 100% alkaline bottom ash only.
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In the following sections pH of standing water and leachate has been discussed separately, while other physiochemical constituents have been grouped and discussed as solids (i.e. TS, TVS, TDS, TSS), nutrients (i.e. TKN, NH4–N, NO3–N, P, K) and metals (i.e. Ca, Mg, Fe, Na). 3.2.1. pH Standing water and leachate pH for all acidic and alkaline blends are presented in Fig. 1. On day 7 (starting day) standing water pH values for B1ac, B2ac, and B3ac (Fig. 1a) were 4.3, 4.3, and 4.7, respectively, while leachate pH for B1ac, B2ac, and B3ac (Fig. 1c) were 3.4, 3.6, and 3.7, respectively. In both cases, initial conditions were very acidic. Initially (day 7), standing water pH for acidic blends was slightly higher than that of leachate due to the higher pH of added de-ionized water. Standing water pH for acidic blend, however, reduced to less than the leachate pH values for all blends at the end of the experiment (day 49). The leachate pH for all acidic blends increased slightly throughout the sampling period due to the addition of near neutral de-ionized water (pH 6.8). Leachate pH from B3ac remained higher than that for B1ac and B2ac throughout the experiment but they were not significantly different from one another. Standing water and leachate pH for alkaline blends were statistically similar (Fig. 1b and d). Standing water and leachate pH for all alkaline blends on day 7 was predominately neutral and increased slightly throughout the sampling events. Standing water pH for alkaline blends increased by 4.6, 4.5, and 4.3% for B1al, B2al, and B3al, respectively. This increase in pH over time
10
10
8
8
6
6
4 BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
2 0
0
7
14
21
28
35
42
4 BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
2 0
49
0
7
14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
10
10
8
8
6
6
pH (-)
pH (-)
3.2. Acidic and alkaline blend ratio effects on standing water and leachate characterization
pH (-)
pH (-)
Potassium concentration for B3ac was also significantly higher than that for the other two blends while K concentration for B2ac was higher but not statistically different from B1ac. For all acidic blends magnesium (Mg) and copper (Cu) concentrations increased with higher CM content of a blend. Concentrations for these two constituents were statistically different among all acidic blends. Iron (Fe) and manganese (Mn) concentrations decreased with increasing CM content and were significantly lower for B2ac and B3ac than B1ac. Trace amounts of TKN, K, calcium (Ca), sodium (Na), and iron (Fe) were detected in the near neutral (pH 6.8) de-ionized water indicating that the de-ionizing equipment likely had reached its treatment capacity. Chemical properties of alkaline BA and CM and de-ionized water prior to saturation are listed in Table 3. As with the acidic blends, TKN and P concentrations were higher for alkaline blends with a higher CM content. Total Kjeldahl Nitrogen concentration was significantly higher for B3al than those for B1al and B2al. For B3al, the P concentration was significantly higher than in B1al but statistically similar to B2al. Phosphorus concentration for B2al was higher than B1al but not significantly different. Potassium concentrations for all alkaline blends were similar. For all alkaline blends, Mg, Mn, sodium (Na) and zinc (Zn) concentrations were not statistically different. Calcium, Cu and Fe concentrations of B1al were significantly lower than those of B2al and B3al but B2al and B3al were not statistically different. De-ionized water was near neutral but trace amounts of TKN, K, Ca, Na, Zn, Fe, and Cu were detected. Additionally, it is evident from Table 2 that raw acidic blends had higher TKN and Zn and generally lower concentrations of all other variables as compared to the raw alkaline blends (Table 3).
4 BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
2
4 BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
2
0
49
0 0
7
14
21
28
35
Sampling event (days)
(c) Leachate, acidic blend
42
49
0
7
14
21
28
35
Sampling event (days)
(d) Leachate, alkaline blend
Fig. 1. Effects of acidic and alkaline BA:CM blends on standing water and leachate pH.
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was due to interaction of de-ionized water with alkaline BA and alkaline CM. Overall, blends with higher CM content showed a small increase in pH compared to blends with lower CM. 3.2.2. Solids Solids content of standing water and leachate from acidic (Table 4) and alkaline (Table 5) blends shows that average TS, TVS, TDS, and TSS concentrations in standing water were significantly lower than those in leachate. Also, average solids content of standing water and leachate for acidic blends was greater than their corresponding solids content in alkaline blends. In general, average TS, TVS, TDS, and TSS concentrations of standing water and leachate from among acidic blends or alkaline blends were statistically similar. However, these concentrations for standing water and leachate from alkaline blends increased with an increase in the CM content. As can be seen from Tables 4 and 5 that most of the solids content of standing
5895
water and leachate from all blends were in the form of dissolved solids (TDS), little or no TSS concentrations were observed among all blends. The effects of blend ratio and sampling event on standing water and leachate TS content for the acidic and alkaline blends are shown in Fig. 2. Standing water TS content for the three acidic blends (Fig. 2a) were significantly lower than that of leachate (Fig. 2c) because contact between the blend and water was greater for leachate than for standing water. At the end of the experiment, standing water TS content for B1ac, B2ac, and B3ac decreased by 69.8, 85.1, and 75.4%, respectively. As CM concentrations within blends increased so did the TS concentration in standing water. Standing water TS content for B3ac was significantly greater than that of B1ac and B2ac, while TS for the B1ac and B2ac were statistically similar (Fig. 2a). This statistical difference was due to gradual mixing of organic matter from the high CM blends with standing water. Over time this was also evident from the darker color of standing
Table 4 Standing water and leachate characteristics for acidic blends averaged over sampling events Variables
TS (g/L) TVS (g/L) TDS (g/L) TSS (g/L) NH4–N (mg/L) NO3–N (mg/L) Ca (mg/L) Mg (mg/L) Fe (mg/L) Na (mg/L)
Standing water
Leachate
BA:CM ratio (%)
BA:CM ratio (%)
95:5
90:10
80:20
95:5
90:10
80:20
B1ac
B2ac
B3ac
B1ac
B2ac
B3ac
0.45b ± 0.52 0.08b ± 0.20 0.48b ± 0.60 0.0c ± 0.0 0.30d ± 0.30 0.77b ± 0.41 80.7c ± 43.3 7.3b ± 16.7 5.6c ± 5.1 47.6c ± 29
1.12b ± 0.95 0.17b ± 0.27 0.88b ± 0.90 0.03c ± 0.08 1.43c ± 1.04 0.90b ± 0.55 139b ± 58.5 36.7b ± 44.2 14.1b ± 3.3 68.3c ± 43.7
13.4a ± 10.3 3.4a ± 2.0 13.3a ± 10.3 0.12b ± 0.08 4.9b ± 2.2 0.90b ± 0.43 526a ± 46.11 125a ± 79.3 215a ± 208 90b ± 38
12.3a ± 9.0 3.4a ± 2.4 12.2a ± 9 0.15b ± 0.08 11.8b ± 4.7 1.32b ± 0.60 526a ± 61.4 201a ± 132 241a ± 292 129ab ± 59.4
11.2a ± 5.9 2.7a ± 1.4 10.9a ± 6.1 0.30a ± 0.14 27.3a ± 9.6 2.4a ± 0.96 563a ± 115 326a ± 234a 293a ± 268 228a ± 131
A
0.40b ± 0.35 0.13b ± 0.16 0.38b ± 0.37 0.0c ± 0.0 0.13d ± 0.08 0.60b ± 0.37 53.6c ± 21.7 1.67b ± 4.1 5.3c ± 4.8 46.6c ± 21.5
±Standard deviation. A Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 6.
Table 5 Standing water and leachate characteristics for alkaline blends averaged over sampling events Variables
TS (g/L) TVS (g/L) TDS (g/L) TSS (g/L) NH4–N (mg/L) NO3–N (mg/L) Ca (mg/L) Mg (mg/L) Fe (mg/L) Na (mg/L)
Standing water
Leachate
BA:CM ratio (%)
BA:CM ratio
95:5
90:10
80:20
95:5
90:10
80:20
B1al
B2al
B3al
B1al
B2al
B3al
0.13b ± 0.08 0.08c ± 0.08 0.13b ± 0.08 0.0a ± 0.0 0.03c ± 0.08 0.70c ± 0.76 33.1b ± 9.3 1.7c ± 2.0 1.5b ± 1.1 202b ± 215
0.17b ± 0.05 0.07c ± 0.05 0.13b ± 0.05 0.0a ± 0.0 0.07c ± 0.12 0.65c ± 0.82 39.7b ± 10.5 4.6c ± 2.5 2.3b ± 1.5 201b ± 222
3.4a ± 1.4 0.60b ± 0.37 3.1a ± 1.8 0.02a ± 0.04 8.6b ± 6.4 1.6b ± 1.25 652a ± 58 79b ± 54.1 9.7a ± 5.9 276a ± 226
3.9a ± 2.3 0.97b ± 0.53 4 a ± 2.2 0.0a ± 0.0 19.1b ± 11.6 3.5b ± 1.25 638a ± 156 112b ± 66.1 4.8a ± 4.0 321a ± 261
5.5a ± 3.3 1.8a ± 0.83 5.3a ± 3.5 0.02a ± 0.04 43.5a ± 24.7 8.3a ± 4.8 641a ± 120 192a ± 73.4 5.7a ± 5.4 473a ± 330
A
0.17b ± 0.08 0.07c ± 0.08 0.17b ± 0.08 0.0a ± 0.0 0.07c ± 0.10 0.68c ± 0.73 37.6b ± 25.8 1.3c ± 3.1 1.2b ± 0.13 192b ± 217
±Standard deviation. A Averages within a row followed by different letters are significantly different at P 6 0.05 level, n = 6.
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3 2 1 0
3 2 1
0
7
14
21
28
35
42
0
49
0
7
14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
49
40
40 BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
30
TS (g/L)
30
TS (g/L)
BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
4
TS (g/L)
4
TS (g/L)
5
BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
20
20 10
10
0
0 0
7
14
21
28
35
42
49
Sampling event (days)
0
7
14
21
28
35
42
49
Sampling event (days)
(d) Leachate, alkaline blend
(c) Leachate, acidic blend Fig. 2. Effects of acidic and alkaline BA:CM blends on standing water and leachate TS.
water observed from blends with higher CM. Standing water TS for the three alkaline blends (Fig. 2b) was considerably lower than that for leachate from the three alkaline blends (Fig. 2d). Highest leachate TS concentration for acidic blend was observed on day 7 (first sampling event) for B1ac (32,500 mg/L), followed by B2ac (28,600 mg/L), and B3ac (21,500 mg/L). The largest decrease in TS concentration occurred between day 7 and day 14 for B1ac, B2ac and B3ac, by 46.5, 43.7, and 32.7%, respectively. From day 21 (third sampling event) until the experiment terminated (day 49), similar values of leachate TS concentration were observed for all blends. Compared to day 7, leachate TS for B1ac, B2ac and B3ac decreased by 84.7 80.5, and 69.3%, respectively, by the end of the experiment (day 49). On the other hand, following the first sampling event (day 7), the highest leachate TS values for alkaline blends were observed for B3al (11,130 mg/L), followed by B2al (7600 mg/L) and B1al (5700 mg/L). After the second sampling event (day 14), like that of acidic TS, a decrease in TS concentrations for these blends was observed. From the third sampling event (day 21) onwards, similar values of leachate TS were observed for all blends. At the end of the alkaline blend experiment, total volume flushed, leachate TS decreased by 81.0, 79.0, and 78.7% for B1al, B2al, and B3al, respectively. Although data not shown, similar trends were observed on the effects of blend ratio and sampling event on standing water and leachate TVS, TDS and TSS concentrations for all acidic and alkaline blends. One notable observation was that after day 14, standing water TDS concentrations were consistently below the USEPA drinking water standard of
500 mg/L for TDS of B1ac and B2ac (USEPA, 1994). Alkaline blend TDS for standing water was lower than the TDS for acidic blends. At the end of the experiment (day 49) concentrations of all solids in standing water and leachate of all blends reduced considerably. 3.2.3. Nutrients Standing water TKN for acidic blends decreased from day 7 to day 49 by 23.5, 45.8, and 17.6% for B1ac, B2ac, and B3ac, respectively, (Fig. 3a). Compared to day 7, standing water TKN for alkaline blends (Fig. 3b) decreased nearly 0.0, 15.0, and 31.8% for B1al, B2al, and B3al, respectively. Standing water and leachate TKN concentrations for alkaline blends were higher than those for acidic blends due to the higher pH (between 7 and 8) of standing water and leachate for all alkaline blends. Acidic blend B3ac had the highest amount of leachate TKN followed by blends B2ac and B1ac (Fig. 3c) indicating higher compost content in a blend yielded higher TKN in leachate. In addition, leachate TKN concentrations from all blends were significantly different. At the end of the experiment, leachate TKN for B1ac, B2ac, and B3ac decreased by 48.2, 48.1, and 48.5%, respectively, from their highest values. For all acidic blends, TKN for leachate was higher than standing water. This was due to lower concentrations of TDS and TVS in standing water than in leachate for all acidic blends. Due to the highest compost content, alkaline blend B3al had the highest leachate TKN concentration followed by B2al and B1al (Fig. 3d). At the same time, TKN concentrations for B1al, B2al, and B3al were significantly different. Generally, greater leachate TKN concentration was observed from alkaline
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BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
15
TKN (mg/L)
TKN (mg/L)
20
10 5 0 0
7
14
21
28
35
42
BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
15 10 5 0
49
0
7
14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
49
250
250
TKN (mg/L)
BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
200
TKN (mg/L)
5897
150 100
BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
200 150 100 50
50
0
0 0
7
14
21
28
35
42
49
0
7
14
21
28
35
Sampling event (days)
Sampling event (days)
(c) Leachate, acidic blend
(d) Leachate, alkaline blend
42
49
Fig. 3. Effects of acidic and alkaline BA:CM blends on standing water and leachate TKN.
blends as compared to those for acidic blends. At the end of the experiment, leachate TKN decreased by 80.9, 82.8, and 87.3% for B1al, B2al, and B3al, respectively, from their highest values. Leachate TKN was significantly higher than standing water TKN for all alkaline blends since greater interaction between organic matter and the de-ionized water within the column allowed for higher leachate TKN. Average standing water and leachate NH4–N concentrations for acidic and alkaline blends are provided in Tables 4 and 5, respectively. For both blends, leachate resulted in significantly higher NH4–N concentration compare to standing water. Significant differences in standing water NH4–N concentrations were observed among acidic blends (Table 4), but not among alkaline blends (Table 5). For acidic blends, NH4–N concentration increased with increased CM content, but for alkaline no clear trend was observed. Ammonium nitrogen for alkaline blends was higher in leachate as compared to acidic blends. This was attributed to mineralization of organic nitrogen for alkaline blends (pH between 7 and 8) versus acidic blends (pH between 3.5 and 5.5). Standing water and leachate NO3–N for acidic (Table 4) and alkaline blends (Table 5) followed a trend similar to NH4–N for these blends. It is noteworthy that even at their highest concentrations, standing water and leachate NO3– N concentrations for all three acidic blends were below the USEPA drinking water standard of 10 mg/L for NO3–N (USEPA, 1994). Standing water NO3–N for all alkaline blends and leachate NO3–N for B1al and B2al was well below the USEPA drinking water standards during the entire experiment (Table 5). By day 28 (data not shown), leachate NO3–N concentration for all alkaline
blends was below the USEPA (1994) drinking water standard of 10 mg/L. Standing water P was not detected for any of the three acidic blends (Fig. 4a). Literature shows that lake eutrophication may occur with water P concentration above 0.02 mg/L (Sharpley, 1999). Since standing water P concentrations were nearly zero, use of these blends in environmental settings may not cause unacceptable P loadings into nearby water resources if water erosion is adequately controlled. Standing water P for alkaline blends was not detected in B1al and B2al (Fig. 4b). On day 49, a standing water P concentration 2.5 mg/L was measured for B3al. Only one of the 4 replicates for blend B3al generated a P concentration of 10 mg/L while no P was detected in the other three replicates, resulting in an average value of 2.5 mg/L. A low concentration of P in standing water is encouraging for the use of these blends in environmental settings. For all alkaline and acidic blends, standing water P was significantly lower than leachate. On day 7, the first sampling event, leachate P for acidic blends B1ac, B2ac, and B3ac was 5, 10, and 10 mg/L, respectively, (Fig. 4c). These values decreased nearly 100% for B1ac and B2ac on day 14 and B3ac on day 21. Blends B1ac and B3ac were statistically different from one another while B1ac and B2ac were statistically similar. Blends B2ac and B3ac were also statistically similar. The mean values for leachate P for B2ac and B3ac were higher than B1ac due to the higher CM content. Alkaline blends B1al and B2al were statistically similar while B1al and B3al, and B2al and B3al were significantly different from each other. Leachate P for B1al was not detected during the duration of the experiment (Fig. 4d). Leachate B2al decreased
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6 4 2
6 4 2
0
0 0
7
14
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35
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0
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14
21
28
35
42
Sampling event (days)
Sampling event (days)
(a) Standing water, acidic blend
(b) Standing water, alkaline blend
30
49
30 BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
20
BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
25
P (mg/L)
25
P (mg/L)
BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
8
P (mg/L)
8
P (mg/L)
10
BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
15 10 5
20 15 10 5
0
0 0
7
14
21
28
35
42
0
49
7
14
21
28
35
Sampling event (days)
Sampling event (days)
(c) Leachate, acidic blend
(d) Leachate, alkaline blend
42
49
Fig. 4. Effects of acidic and alkaline BA:CM blends on standing water and leachate P.
66.7% while B3al increased 1.4%. Like the acidic blends, leachate P for alkaline blend B3al was higher than those of B1al and B2al due to the higher CM concentration in B3al. Leachate P for alkaline blends was higher than acidic blends due to higher P content of raw, unsaturated alkaline blends (especially, B1al and B2al) and due to high pH for alkaline blends versus acidic blends.
500
300
BA:CM=95:05 SW (B1ac) BA:CM=90:10 SW (B2ac) BA:CM=80:20 SW (B3ac)
K (mg/L)
400
K (mg/L)
As can be seen from Fig. 5a that for acidic blends, standing water K was the highest for B1ac and B2ac on day 7 and decreased by 52.0 and 89.7%, respectively, by the end of the sampling events. Leachate K for acidic blend (Fig. 5c) was highest for B1ac, B2ac, and B3ac on day 7 (first sampling event). Leachate K concentration for acidic blend B3ac was significantly higher than B1ac and B2ac due to the
300 200
BA:CM=95:05 SW (B1al) BA:CM=90:10 SW (B2al) BA:CM=80:20 SW (B3al)
200
100
100 0
0
7
14
21
28
35
42
0
49
0
7
14
Sampling event (days)
(a) Standing water, acidic blend
28
35
42
49
(b) Standing water, alkaline blend
2000
2000
K (mg/L)
BA:CM=95:05 L (B1ac) BA:CM=90:10 L (B2ac) BA:CM=80:20 L (B3ac)
1500
K (mg/L)
21
Sampling event (days)
1000 500
BA:CM=95:05 L (B1al) BA:CM=90:10 L (B2al) BA:CM=80:20 L (B3al)
1500 1000 500
0
0 0
7
14
21
28
35
42
49
0
7
14
21
28
35
Sampling event (days)
Sampling event (days)
(c) Leachate, acidic blend
(d) Leachate, alkaline blend
Fig. 5. Effects of acidic and alkaline BA:CM blends on standing water and leachate K.
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higher CM content of this blend. By the end of the experiment, leachate K for B1ac, B2ac, and B3ac decreased by 81.5, 80.5, and 79.5%, respectively. The highest leachate K for alkaline blends was also observed on day 7 for B1al, B2al, and B3al (Fig. 5d). By the end of the experiment, leachate K for B1al, B2al, and B3al decreased 90.5, 90.8, and 90.2%, respectively. For all acidic and alkaline blends, leachate K was significantly higher than that of standing water due to greater interaction between organic matter and the de-ionized water within the column. Standing water K for alkaline blends was the highest on day 14 and by the end of the experiment (day 49) decreased by 74.1, 35.5, and 57.0% for B1al, B2al and B3al, respectively, (Fig. 5b). Leachate K for B3al was higher than B1al and B2al. All alkaline blends were significantly different from one another. A similar trend was seen in the acidic blends. Standing water and leachate K for alkaline blends was higher than acidic blends due to higher K content of raw blends and due to high pH for alkaline blends versus acidic blends (Tables 2 and 3). 3.2.4. Metals Average concentrations of standing water and leachate Ca, Mg, Fe, and Na are shown in Tables 4 and 5 for acidic and alkaline blends, respectively. Concentrations of these elements in standing water were significantly lower than that in leachate. Increasing time resulted in decreasing concentrations of all the elements, except Ca concentration in acidic blends (data not shown). With the exception of Na, standing water and leachate concentrations of Ca, Mg, and Fe were generally greater in acidic blends compared to alkaline blends (Tables 4 and 5). This occurred even though raw acidic blends (Table 2) had lower concentrations of these elements than raw alkaline blends (Table 3). This may be the result of increased leaching and availability of these traces metals due to very low pH (between 3.5 and 5.5) for acidic blends of BA and CM. Meima and Comans (1999) observed reduced leaching of these and other trace elements due to reduced solubility of these elements as a result of near neutral pH of BA. Therefore, possibility of greater leaching and availability of trace metals from low pH blends of BA and CM must be considered before using them as a soil amendment. Additionally, decreased soil pH as a result of these acidic amendments may depress the growth of some plant species such as maize, wheat, tomato and zinger (Islam et al., 1980). 4. Summary and conclusions Three acidic blends of bottom ash and composted dairy manure (BA: CM%, v/v) namely: B1ac (95:5%), B2ac (90:10%), and B3ac (80:20%) and three alkaline blends namely: B1al (95:5%), B2al (90:10%), and B3al (80:20%) were evaluated for potential use as a soil amendment material. The blends were subjected to constant head water table management using de-ionized water. Based on the findings of this study it was concluded that the amount
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of CM in acidic and alkaline blends impacted the concentrations of most of the physicochemical parameters tested in raw blends, leachate, and standing water. Concentrations of nearly all chemicals were lower in standing water (top) compared to leachate (bottom) for acidic and alkaline blends. For both acidic and alkaline blends, concentrations of almost all constituents were greatest for the first samples (day 7) of leachate and standing water but reduced significantly at the end of this study (day 49). Standing water and leachate concentrations of all solids for alkaline blends were lower than those for the acidic blends. Standing water and leachate TKN, NH4–N and NO3–N concentrations for alkaline blends were higher than those for acidic blends due to higher pH (between 7 and 8) of standing water and leachate for all alkaline blends. Standing water and leachate NO3–N concentrations for all acidic blends and for alkaline blends B1al and B2al were below the USEPA drinking water standard for nitrate. Phosphorus concentrations were low in leachate and nonexistent in standing water for acidic and alkaline blends. In light of these findings it is suggested that acidic and alkaline blends B1ac, B1al, B2ac and B2al may be considered as a soil amendment substitute. However, reduced pH of acidic blend amended soil may depress the growth of plant species that are susceptible to low pH. Under saturated conditions, acidic blend amended soils may also release greater concentrations of trace metals to the environment as compared to alkaline blend amended soils. Acknowledgements The authors would like to thank the team of the ISG, Resources Inc. Jewett, Texas for their corporation and supply of bottom ash used in this study. These studies were conducted in laboratories of the Department of Biological and Agricultural Engineering at the Texas A&M University, College Station, Texas. References Adriano, D.C., Page, A.L., Elseewi, A.L., Chang, A.C., Straughan, I., 1980. Utilization and disposal of fly ash and other coal residues in terrestrial ecosystems. Journal of Environmental Quality 9, 333–344. Angel, C.E., Feagley, S.E., 1987. The effect of lime and fertilizer on four lignite overburdens under non-drained conditions: 1. Yield and nutrient concentration of common bermudagrass. Communication in Soil Science and Plant Analysis 18, 963–980. APHA, 2005. Standard Methods for Examination of Water and Wastewater, 21st ed. American Public Health Association, New York. ASAE Standards, 2005. D384.2, Manure Production and Characteristics. American Society of Agricultural Engineers, St. Joseph, Michigan. Butler, S.H., Bearce, B.C., 1995. Greenhouse rose production in media containing coal bottom ash. Journal of Environmental Horticulture 13, 160–164. Chen, Y., Gottesman, A., Aviad, T., Inbar, Y., 1991. The use of bottomash coal-cinder amended with compost as a container medium in horticulture. International Society for Horticultural Science 294, 173– 181. Hach, 1997. Water Analysis Handbook, third ed. Hach Company, Loveland, Colorado, USA.
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Haug, R.T., 1993. The Practical Handbook of Compost Engineering. Lewis Publishers, Boca Raton, Florida. Islam, A.K.M.S., Edwards, D.G., Asher, C.J., 1980. pH optima for crop growth results of a flowing solution culture experiment with six species. Plant and Soil 54, 339–357. Meima, J.A.R., Comans, N.J., 1999. The leaching of trace elements from municipal solid waste incinerator bottom ash at different stages of weathering. Applied Geochemistry 14, 159–171. Miner, J.R., Humenik, F.J., Overcash, M.R., 2000. Managing livestock waste to preserve environmental quality. Iowa State University Press, Ames, Iowa. Mukhtar, S., Kenimer, A.L., Sadaka, S.S., Mathis, J.G., 2003. Evaluation of bottom ash and composted dairy manure as a soil amendment material. Bioresource Technology 89, 217–228. Nelson, D.W., Sommers, L.E., 1973. Determination of total nitrogen in plant material. Agronomy Journal 65, 109–112.
Rynk, R., 1992. On-Farm Composting Handbook. Northeast Regional Agricultural Engineering Service. Publication Number: NRAES-54, Ithaca, New York. Sell, N., McIntosh, T., Severance, C., Peterson, A., 1989. The agronomic land spreading of coal BA: using a regulated solid waste as a resource. Resources, Conservation and Recycling 2, 119–129. Sharpley, A.N., 1999. Agricultural phosphorus and eutrophication. Agricultural Research Service. Publication No. ARS-149.1999. TFHRC. Turner-Fairbank Highway Research Center website, http:// www.tfhrc.gov/hnr20/recycle/waste/cbabs1, (accessed on January 2005). USEPA, 1994. Water Quality Standards Handbook, second ed. Update 1. Order Number: EPA/823-B-94-006. Woodard, M.A., Bearce, B., Cluskey, C., Townsend, S.E.C., 1993. Coal bottom ash and pine wood peelings as root substrates in a circulating nutriculture system. Horticultural Science 28, 636–638.