城市污泥与水葫芦堆肥性质变化规律

采用仓式好氧堆肥方法,研究了不同比例的城市污泥和水葫芦混合物料堆肥过程中各项评价参数(温度、含水率、pH、有机质和总氮)的变化规律。结果表明:堆肥过程中,堆体温度、含水率变化过程为先上升,再下降;堆体的pH和总氮变化过程为先降低再升高,最后趋于稳定。有机质含量在堆肥48 h内迅速下降,之后缓慢下降。对小堆体,大风量更有利于有机质的降解,但不利于氮素的保存。当m(污泥)∶m(水葫芦)为4∶1时的堆肥效果要优于m(污泥)∶m(水葫芦)为2∶1时的堆肥效果。     

调理剂对堆肥产品重金属生物有效性的影响

城市污泥中重金属含量及其生物有效性是限制污泥农用的主要因素,因此,研究污泥堆肥化处理过程中重金属生物有效性,对污泥的农用具有重要意义。实验以城市污泥为原料,以菌菇渣和秸秆为调理剂,设置4个处理:A(污泥∶菌菇渣∶秸秆=1∶0.4∶0.025)、B(污泥∶菌菇渣∶秸秆=1∶0.3∶0.025)、C(污泥∶秸秆=1∶0.12)和D(污泥∶秸秆=1∶0.09),进行好氧堆肥实验,采用BCR顺序提取法测定各种形态的重金属,研究堆肥前后重金属形态的变化规律。结果表明,城市污泥中Cu、Ni、Pb和Cr主要以可氧化态及残渣态存在,生物有效性较低,而Zn和Cd主要以酸溶态和可还原态存在,生物有效性较高;堆肥过程显著降低了Cu、Zn、Ni和Pb的生物有效性,并改变了Cu、Zn、Ni、Pb、Cr和Cd的形态分布,使污泥中的Cu、Zn、Ni、Pb和Cd向着更稳定的可氧化态或残渣态转变;污泥经过堆肥处理后,Cu、Zn和Ni 3种重金属生物有效性关系为:ABCD,与其他处理相比,处理A残渣态的Pb和Cr增加比例较多,综合来看,处理A对重金属生物有效性的降低最为明显,重金属钝化效果最佳。     

餐厨垃圾自然升温堆肥工艺研究

为研究餐厨垃圾发酵生产有机肥的可行性,优化堆肥发酵工艺,对堆体C/N、辅料、翻堆频率、粒径和pH值等可变因素进行了堆肥研究,结果表明,餐厨垃圾堆肥发酵的最佳条件为:C/N 20～27,以粒径<5 mm的稻草为辅料,含水率(65±5)%,翻堆频率1次/d(以保持堆体温度不超过70℃),一个堆肥周期内翻堆15～20次,堆肥周期为20 d左右。产品理化指标检测符合有机肥料标准(NY525-2002),且堆肥工艺重复性好,生产成本低,具有较高的应用价值。     

不同添加剂下污泥堆肥化处理氮素变化研究

研究采用了高温好氧堆肥的方法,将城市生活污泥与不同比例花生壳、干污泥混合,在密闭反应器中堆肥,研究堆肥过程中氨气挥发量以及各种形态氮素含量的变化情况。结果表明,初始含水率调整在60%左右,综合堆体温度、含水率下降、氨气挥发量及氮素转化损失量,在污泥处理中添加8.3%花生壳+41.7%干污泥的处理效果最佳,其单位时间氨气挥发量为对照处理的1/5,全氮损失8.9%。在实际生产中,可以将堆肥产物干污泥循环使用,再辅以少量花生壳等干物料进行污泥堆肥,可达到降低成本的效果。     

一种新型可控堆肥反应器系统的快速厌氧堆肥研究

采用自制的好厌氧堆肥综合反应器系统进行厌氧堆肥实验。堆肥物料质量比为:污泥∶木屑∶聚丙稀酸钠(PAAS)=1∶0.15∶0.01,活性干酵母粉以50 mL/5 g的比例用5%生理盐水稀释后,按照5 g酵母粉/kg物料的比例掺入上述混合堆料中。研究表明,采用新型反应系统用于厌氧堆肥,能在21 d内完成一个堆肥周期,且堆肥过程各指标变化规律性强,堆肥效果稳定。     

辅料比例对餐厨垃圾好氧堆肥及微生物特性的影响

添加不同质量米糠为堆肥辅料与餐厨垃圾混合进行好氧堆肥,通过调节堆体含水率和C/N,旨在考察不同辅料比例条件下堆肥理化特性变化规律及微生物酶活变化情况。结果表明,餐厨垃圾∶米糠质量比分别为3∶1、4∶1和5∶1的堆体均能进入高温阶段,高温阶段持续5~6 d,其中3∶1处理升温最快,最高温度可达70.9℃。堆体pH上升至7.5~8.5,初期水萃COD/TN快速下降至10左右,周期结束时含水率和有机质削减量分别为21%~30%和27%~37%。5∶1处理C/N下降最多,GI50%,达到基本腐熟,而其他2个处理腐熟效果不佳。在堆肥过程中,与水解进程相关的蔗糖酶活性高峰出现在升温阶段,而与氧化还原过程相关的脱氢酶活性随时间不断增大,腐熟度增加。     

核桃壳骨架构建剂对污泥脱水性能的影响

污泥最终处置的困难在于提高泥饼的含固量和降低其含水率。研究用核桃壳做骨架构建剂对污泥进行调理对污泥脱水性能改善的影响。通过测定污泥比阻(SRF),毛细吸水时间(CST)以及抽滤后污泥含水率,探究核桃壳骨架构建剂对污泥脱水性能的影响。结果表明,采用核桃壳做骨架构建剂调理污泥的最佳添加量为4∶6(核桃壳与污泥干重比),最佳粒径为0.25 mm。用真空抽滤脱水,核桃壳调理后污泥的含水率明显降低。含水率为97.5%的原泥经过29 min真空抽滤后泥饼含水率降至70.52%;按核桃壳与污泥干重比4∶6,添加粒径0.25 mm的核桃壳后,泥饼含水率降为63.57%,SRF由初始的3.73×1013m/kg,降为调理后的1.06×1013m/kg。     

分选垃圾、菜市场垃圾和腐熟污泥混合堆肥过程中氮素转化和损失研究

设计了两组高温堆肥实验,A组分选垃圾和腐熟污泥按质量比1∶1混合,B组分选垃圾、菜市场垃圾和腐熟污泥按质量比1∶1∶1混合。结果表明:A、B两组的堆体温度大于55℃的时间均不低于3d,满足卫生学要求,能够实现无害化处理,B组堆体高温持续时间比A组长近10d。堆肥过程中,A、B两组堆体TN和有机氮总体逐渐降低,氨氮先增加后减少,硝态氮则一直上升;A、B两组堆体N2O的释放主要集中在堆肥前期,堆肥前7天N_2O的释放量均达到总量的90%以上,堆肥过程中B组的氮素损失率为30.65%,低于A组的氮素损失率(48.02%)。     

红薯渣和城市污泥混合发酵产酸强化污水脱氮除磷

投加红薯渣促进城市污泥厌氧发酵产酸量,并将所得有机酸应用到污水处理外加碳源,强化污水脱氮除磷效果。实验结果表明,红薯渣和城市污泥混合发酵产酸比单一污泥发酵效果更好,有机酸产量可提高3倍左右,且做补充碳源时品质好,发酵液中COD∶TN∶TP约为160∶1∶1.6。将混合发酵所得有机酸应用到污水脱氮除磷外加碳源,结果表明,混合发酵所得有机酸优于污泥热碱预处理碳源和乙酸钠,污水处理出水中平均COD、TN和TP分别为(32.1±1.45)、(4.8±0.52)和(0.7±0.18)mg/L,TN和TP去除率分别达到(87.2±1.20)%和(90.0±0.18)%。因此,红薯渣的投加,可以大大提高城市污泥发酵产酸效果,优化发酵液碳源的品质。     

添加腐熟污泥对生活垃圾堆肥物料理化性质及温室气体释放规律的影响

研究了添加腐熟污泥对生活垃圾堆肥物料理化性质及温室气体释放规律的影响。结果表明:(1)在生活垃圾中添加腐熟污泥进行堆肥,可降低堆肥物料的含水率,缩短整个堆肥周期;添加腐熟污泥还可以缓解堆体的酸化程度,促进有机质的降解,使C/N更适合微生物的生长和繁殖。(2)CO_2和CH_4两种温室气体的释放主要集中在堆肥高温期,CO_2释放量随腐熟污泥添加量的增加而增加,而CH_4释放量随腐熟污泥添加量的增加而减少。     

过量生石灰对污泥含水率和有机物含量的影响

为了研究生石灰(氧化钙,CaO)处理活性污泥对污泥含水率和有机物含量的影响,通过向南京某城市污水处理厂出厂污泥投加过量CaO进行脱水实验,测定投加CaO后污泥的含水率;烘干后的脱水污泥进行热重实验,研究CaO投加量对污泥中有机组分含量的影响.脱水实验表明:随着CaO与污泥质量比的增大,污泥含水率迅速减小,当质量比达到1.5时,污泥达到完全脱水;投加过量CaO的脱水污泥呈干燥的粉末状,粒度均匀,可作为水泥生产的辅料。热重实验表明:投加CaO后单位干泥失重百分比随CaO与污泥质量比增大而逐渐减小,向污泥中投加CaO有利于污泥中有机组分的释放和去除,实现污泥的稳定化。     

湿污泥在流化床中干燥特性

在鼓泡流化床干燥器内,床料采用0～1 mm的石英砂,以热空气作为干燥介质,对城市污水污泥的流态化干燥特性进行实验研究。通过控制送风温度、流化风量、加料量、污泥粒径等参数,研究在不同工况条件下床温以及干污泥含水率的变化情况。结果表明,随着送风温度的升高,床温升高,干污泥含水率下降,最终趋向于一个稳定值8%。床温随流化风量的增加先是减小而后升高,干污泥的含水率随流化风量的增加先是降低而后增大。当加料量从11 kg/h增加到13kg/h时,干污泥的含水率基本没有变化,当加料量超过13 kg/h时,干污泥的含水率从8.1%开始呈递增趋势。随污泥粒径的增大,床温升高,干污泥含水率也随之升高。     

Bioremediation of diesel-contaminated soil with composting

The major objective of this research was to find the appropriate mix ratio of organic amendments for enhancing diesel oil degradation during contaminated soil composting. Sewage sludge or compost was added as an amendment for supplementing organic matter for composting of contaminated soil. The ratios of contaminated soil to organic amendments were 1:0.1, 1:0.3, 1:0.5, and 1:1 as wet weight basis. Target contaminant of this research was diesel oil, which was spiked at 10,000 mg/kg sample on a dry weight basis. The degradation of diesel oil was significantly enhanced by the addition of these organic amendments relative to straight soil. Degradation rates of total petroleum hydrocarbons (TPH) and n-alkanes were the greatest at the ratio of 1:0.5 of contaminated soil to organic amendments on wet weight basis. Preferential degradation of n-alkanes over TPH was observed regardless of the kind and the amount of organic amendments. The first order degradation constant of n-alkanes was about twice TPH degradation constant. Normal alkanes could be divided in two groups (C10-C15 versus C16-C20) based on the first order kinetic constant. Volatilization loss of TPH was only about 2% of initial TPH. Normal alkanes lost by volatilization were mainly by the compounds of C10 to C16. High correlations (r=0.80-0.86) were found among TPH degradation rate, amount of CO2 evolved, and dehydrogenase activity.     

Translocation of metals and its effects in the tomato plants grown on various amendments of tannery waste: evidence for involvement of antioxidants

A field experiment was conducted to study the effect of different amendments of tannery sludge on physiological and biochemical parameters of tomato plant (Lycopersicon esculentum L. Mill). The accumulation of metals (Cr, Fe) in different parts of tomato plants grown on tannery sludge amended soil increased in a concentration and duration-dependent manner. The accumulation of both the metals was found lowest in the fruits of the plant. The statistical analysis of the results showed an increase in chlorophyll and protein contents in lower sludge amendment ratio at all exposures followed by a decrease at highest (100%) sludge amendment ratio. Lipid peroxidation enhanced in both root and leaves of sludge grown plants of tomato at all the sludge amendments and exposure periods, which is evidenced by increased malondialdehyde content, however the maximum increase was found in the roots (43.63%) and leaves (56.66%) of the plant grown on 100% tannery sludge at 60 d, over respective controls. The level of antioxidants, cysteine, non-protein thiol and ascorbic acid increased in the sludge grown plants of tomato to cope up with stress induced by the excess amount of the heavy metals present in the tannery sludge. The maximum increase was found in cysteine content (75.53% in the leaves), non-protein thiol content (92.68% in the roots) and ascorbic acid content (29.66% in the roots) of the plant at 75% tannery sludge after 30 d. The tomato plants were found well adopted for minimizing damage induced by reactive oxygen species, when grown on tannery sludge amendments in the present study.     

Heavy metal mobility in runoff water and absorption by eggplant fruits from sludge treated soil

Sewage sludge addition to agricultural lands requires judicious management to avoid environmental risks arising from heavy metal and nitrate contamination of surface water and accumulation in edible plants. A field study was conducted on a silty-loam soil of 10% slope at Kentucky State University Research Farm. Eighteen plots of 22 x 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge and yard waste compost mix (SS-YW) at 15 t acre(-1), six plots were mixed with sewage sludge (SS) at 15 t acre(-1), and six unamended plots that never received sludge were used for comparison purposes. Plots were planted with eggplant, Solanum melongena L. as the test plant. The objectives of this investigation were to: 1) assess the effect of soil amendments on the transport of NO3, NH4, and heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) into surface water; 2) investigate the effect of soil amendments on heavy metal bioavailability in eggplant fruits at harvest; and 3) assess chemical and physical properties of soil following addition of soil amendments and their impact on the yield and quality of eggplant fruit. SS-YW treatments reduced runoff water by 63% while plots incorporated with sewage sludge alone reduced runoff water by 37% compared to control treatment. The SS-YW treatments transported more mineral nitrogen (NO3-N and NH4-N) in runoff water than SS treatments. Total marketable yield (lbs acre(-1)) and number of eggplant fruits were greatest in SS-YW treatments. This response may be due to improved soil porosity, water, and nutrient retention of the soil amended with SS-YW mixture. Concentrations of heavy metals in soil amended with sludge were below the U.S. Environmental Protection Agency (USEPA) limits. Chromium, Ni, Zn, and Cu were taken up by eggplant fruits but their concentrations were below the Codex Commission allowable levels.     

Response of antioxidants in sunflower (Helianthus annuus L.) grown on different amendments of tannery sludge: its metal accumulation potential

The interaction of metals present in tannery waste and their tolerance in the plants of sunflower (Helianthus annuus L.) was studied in the present paper under field conditions. Effects of 100% tannery sludge and various amendments of tannery sludge (10%, 25%, 35%, 50%, 75%) along with one set of control were studied on the physiological and biochemical parameters of the plant along with their metal accumulation potential after 30, 60 and 90 d after sowing. The plants of H. annuus were found effective in the accumulation of metals (Cr, Fe, Zn and Mn) in roots, shoots and leaves, however, the level of toxic metal, Cr was found below detection limit in the seeds of the plant. The oil was extracted from the seeds of the plant and the level of oil content was increased up to 35% tannery sludge as compared to control followed by decrease at higher tannery sludge ratio. An increase in the chlorophyll, protein, cysteine, non-protein thiol and sugar contents was observed at the lower amendment of tannery sludge at initial exposure periods followed by decrease than their respective controls. Malondialdehyde content in the roots and leaves was increased beyond 50% sludge amendments at all the exposure periods as compared to control. However, proline and ascorbic acid contents of the roots and leaves of the plant increased at all the exposure periods and sludge amendments, compared to their respective controls.     

Chemical fractionation and heavy metal accumulation in the plant of Sesamum indicum (L.) var. T55 grown on soil amended with tannery sludge: Selection of single extractants

A pot experiment was carried out to study the single and sequential extractions of metals in different tannery sludge amendment and the potential of the plant of Sesamum indicum L. var. T55 (sesame) for the removal of metals from tannery waste contaminated site. The metal extraction efficiency obtained with each extractants was slightly different and follow the order; EDTA>DTPA>NH(4)NO(3)>NaNO(3)>CaCl(2). The correlation analysis between extractable metals in the different amendments of sludge and metal accumulation in the plant (lower and upper parts) showed better correlation for most of the tested metals with EDTA extraction. In this study, a sequential extraction technique was applied on different amendments of tannery sludge. The results showed that Mn, Zn, Cr and Cd were mostly associated with Fe-Mn oxide fraction in most of the amendments, K and Ni was found in residual (RES) fraction, Fe and Cu was bound with organic matter (OM) and RES fractions and Na was associated with carbonate (CAR) fraction. The metal accumulation after 60 d of growth of the plant was found in the order of K>Na>Fe>Zn>Cr>Mn>Cu>Pb>Ni>Cd and its translocation was found less in upper part. The accumulation of toxic metals (Cr, Ni and Cd) in the plants was found to increase with increase in sludge ratio, in contrast, the accumulation of Pb decreased. In view of growth parameters and metal accumulation in the plant, it was observed that lower amendments (25%) of tannery sludge were found suitable for the phytoremediation of most of the studied metals.     

Heavy metal mobility in runoff water and absorption by eggplant fruits from sludge treated soil

Sewage sludge addition to agricultural lands requires judicious management to avoid environmental risks arising from heavy metal and nitrate contamination of surface water and accumulation in edible plants. A field study was conducted on a silty-loam soil of 10% slope at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge and yard waste compost mix (SS-YW) at 15 t acre^?1, six plots were mixed with sewage sludge (SS) at 15 t acre^?1, and six unamended plots that never received sludge were used for comparison purposes. Plots were planted with eggplant, Solanum melongena L. as the test plant. The objectives of this investigation were to: 1) assess the effect of soil amendments on the transport of NO₃, NH₄, and heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) into surface water; 2) investigate the effect of soil amendments on heavy metal bioavailability in eggplant fruits at harvest; and 3) assess chemical and physical properties of soil following addition of soil amendments and their impact on the yield and quality of eggplant fruit. SS-YW treatments reduced runoff water by 63% while plots incorporated with sewage sludge alone reduced runoff water by 37% compared to control treatment. The SS-YW treatments transported more mineral nitrogen (NO₃-N and NH₄-N) in runoff water than SS treatments. Total marketable yield (lbs acre^?1) and number of eggplant fruits were greatest in SS-YW treatments. This response may be due to improved soil porosity, water, and nutrient retention of the soil amended with SS-YW mixture. Concentrations of heavy metals in soil amended with sludge were below the U.S. Environmental Protection Agency (USEPA) limits. Chromium, Ni, Zn, and Cu were taken up by eggplant fruits but their concentrations were below the Codex Commission allowable levels.     

Adsorption/Desorption of Copper by a Sandy Soil Amended with Various Rates of Manure,Sewage Sludge,and Incinerated Sewage Sludge

Organic amendments are sometimes applied to agricultural soils to improve the physical, chemical, and microbiological properties of the soils. The organic fractions in these soil amendments also influence metal reaction, particularly the adsorption and desorption of metals, which, in turn, determine the bioavailability of the metals and hence their phytotoxicities. In this study, a Quincy fine sandy (mixed, mesic, Xeric Torripsamments) soil was treated with 0 to 160 g kg^?1 rates of either manure, sewage sludge (SS), or incinerated sewage sludge (ISS) and equilibrated in a greenhouse at near field capacity moisture content for 100 days. Following the incubation period, the soil was dried and adsorption of copper (Cu) was evaluated in a batch equilibration study at either 0, 100, 200, or 400 mg L^?1 Cu concentrations in a 0.01M CaCl₂ solution. The desorption of adsorbed Cu was evaluated by three successive elutions in 0.01M CaCl₂. Copper adsorption increased with an increase in manure rates. At the highest rate of manure addition (160 g kg^?1 soil), Cu adsorption was two-fold greater than that by the unamended soil at all rates of Cu additions. With increasing rates of Cu additions, the adsorption of Cu decreased from 99.4 to 77.6% of Cu applied to the 160 g kg^?1 manure amended soil. The desorption of Cu decreased with an increase in rate of manure amendment. Effects of sewage sludge amendments on Cu adsorption were somewhat similar to those as described for manure additions. Likewise, the desorption of Cu was the least at the high rate of SS addition (160 g kg^?1), although at the lower rates there was not a clear indication of the rate effects. In contrast to the above two amendments, the ISS amendment had the least effect on Cu adsorption. At the highest rate of ISS amendment, the Cu adsorption was roughly 50% of that at the similar rate of either manure or SS amendments, across all Cu rates.     

Biodegradation of phthalate esters in polluted soil by using organic amendment

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg(-1)) and DEHP (100 mg kg(-1)) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1-0.45 μm to 500-2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.