An explanation for the apparent losses of metals in a long-term field experiment with sewage sludge

Large losses of metals applied to soil in metal-contaminated sewage sludge have been reported. The potential pathways of loss, including lateral movement from treated plot areas, have not been examined. A field experiment, which started in 1942, was investigated to determine the amount of lateral movement of zinc, cadmium, copper, nickel, chromium and lead due to conventional cultivation processes. A two-dimensional 'dispersion' model (i.e. movement of soil due to cultivation) fitted well to the observed movement of metals, and gave coefficients for movement of 0.24 and 0.13 m(2) per tillage operation in dimensions parallel or perpendicular to the direction of ploughing, respectively. For testing purposes, the model was used to predict the concentrations of metals in specific areas of a plot or average concentrations for whole plots at different points in time. The concentrations measured in soil samples agreed well with the predicted values. Finally, the model was also used to estimate the proportion of the metal load applied between 1942 and 1961 that remained in the 0-27 cm cultivated layer in 1985. About 80% was accounted for: this large recovery is of great relevance to the long-term disposal of metal-contaminated wastes to land. Detailed analyses of soil profile samples showed that approximately 1% of the metals applied had moved 3.5 cm below the plough layer or less, but there was no evidence of accumulation of metals in deeper horizons down to 46 cm. These results are discussed in relation to the other potential losses of metals in the experiment.     

Polynuclear aromatic hydrocarbons in crops from long-term field experiments amended with sewage sludge

This study reports on the polynuclear aromatic hydrocarbon (PAH) content of crop plants grown at three different field experiments where controlled additions of sewage sludge were made a number of years ago. Archived samples of several crops have been analysed from sludge-amended and unsludged control plots for 15 PAH compounds. Root crops and above ground plant parts were available for several years following the last applications of sludge. Although the soil PAH burden increased substantially due to sewage sludge additions, and residues of these compounds have persisted in the soils for many years, increased PAH concentrations relative to the unsludged controls were not consistently detected in plant tissues. Plant samples were relatively enriched with low molecular weight compounds such as acenaphthene/fluorene nd phenanthrene. Various lines of evidence indicate that PAHs detected in above ground plant parts are chiefly derived from atmospheric inputs, while PAHs detected in root crops probably arise from adsorption to the root surface.     

Cadmium availability to wheat grain in soils treated with sewage sludge or metal salts

Grain Cd concentrations were determined in wheat (Triticum aestivum L.) grown in 1999, 2001 and 2003, at six sludge cake field experiments. Three of these sites also had comparisons with Cd availability from metal amended liquid sludge and metal salts. Grain Cd concentrations in all years and at all sites were significantly linearly correlated with NH4NO3 extractable Cd and soil total Cd (P<0.001). Soil extractability was greater in the liquid sludge and metal salt experiments than in the cake experiments, as were grain Cd concentrations. Across all the sites, NH4NO3 extractable soil Cd was no better at predicting grain Cd than soil total Cd. Stepwise multiple linear regression analysis showed that soil total Cd, pH and organic carbon were the only significant (P<0.001) variables influencing wheat grain Cd concentrations, explaining 78% of the variance across all field experiments (1408 plots). This regression predicted that the current UK soil total Cd limit of 3 mg kg(-1) was not sufficiently protective against producing grain above the European Union (EU) grain Cd Maximum Permissible Concentration (MPC) of 0.235 mg Cd kg(-1) dry weight, unless the soil pH was > 6.8. Our predictions show that grain would be below the MPC with > 95% confidence with the proposed new EU draft regulations permitting maximum total Cd concentrations in soils receiving sludge of 0.5 mg kg(-1) for soils of pH 5-6, 1 mg kg(-1) for soils of pH 6-7, and 1.5 mg kg(-1) for soils of pH > or = 7.     

Polybrominated diphenyl ethers and organochlorine pesticides in sewage sludge of wastewater treatment plants in China

The concentrations of chemicals in sewage sludge from wastewater treatment plants (WWTPs) may relate to their levels of use and environmental pollution in the region. In this work, sludge samples were collected from 31 WWTPs in 26 cities in China and analyzed for polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). The concentrations of SigmaPBDE (sum of congeners 17, 28, 47, 66, 71, 85, 99, 100, 138, 153, 154, and 183) ranged from 6.2 to 57ng/g (dw). The concentration of decabromodiphenyl ether (BDE-209) ranged from below limit of detection (LOD) to 1109ng/g (dw) (with a median of 27ng/g (dw)), and averaged 55% (median 69%) of the total PBDEs. These levels are about 10-100 times lower than those found in Europe and North America. PBDE levels in sludge were not found to depend on the location and capacity of the WWTPs. Concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDTs) and its major degradation products, and hexachlorobenzene (HCB) ranged from below detection limit to 167ng/g (dw), 11 to 1065ng/g (dw), and 7.5 to 319ng/g (dw), respectively. The major DDT degradation products were p,p'-DDE and p,p'-DDD. The major hexachlorocyclohexane (HCH) isomer in sludge is beta-HCH, reflecting its higher affinity to solids and resistance to degradation than other isomers.     

Influence of the application of sewage sludge on the degradation of pesticides in the soil

A study was made of the influence of the application of sewage sludge on the degradation of pesticides in the soil. Two kinds of sludge were used, with different characteristics, one from an urban treatment plant and one from a food processing plant. Three organophosphorus insecticides, fenitrothion, diazinon and dimethoate, were studied. The relative importance was determined of the chemical and biological degradation processes, which involved experiments on soil and sterile soil samples. A comparative study was also made of the degradation of pesticide residues and the evolution of the microbial population. The application of sludge seems to have a complex effect on the degradation of pesticides, determined by the bioavailability and biodegradability of their active ingredient. The biodegradation of pesticide residues brings about alterations in the microorganism population of the soil.     

Occurrence of multiclass UV filters in treated sewage sludge from wastewater treatment plants

Many substances related to human activities end up in wastewater and accumulate in sewage sludge. So far, there is only one extensive survey on the occurrence of UV filter residues in sewage sludge. However, more data are required to draw a reliable picture of the fate and effects of these compounds in the environment. This study attempts to fill this gap through the determination of selected UV filters and derivatives namely 4-methylbenzylidenecamphor, benzophenone-3, octocrylene, ethylhexylmethoxycinnamate, ethylhexyldimethyl PABA, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, and 4,4′-dihydroxybenzophenone in treated sewage sludge.The target compounds were extracted using pressurized liquid extraction and after this, determined by ultra high resolution liquid chromatography-tandem mass spectrometry. The determination was fast and sensitive, affording limits of detection lower than 19 ng g⁻¹ dry weight (dw) except for 2,4-dihydroxybenzophenone (60 ng g⁻¹ dw). Good recovery rates, especially given the high complexity of sludge matrix (between 70% and 102% except for 2,4-dihydroxybenzophenone (30%)) were achieved.The application of developed method allowed reporting for the first time the occurrence of two major degradation products of benzophenone-3 that have estrogenic activity in sewage sludge: 4,4′-dihydroxybenzophenone (in 5/15 WWTPs) and 4-hydroxybenzophenone (in 1/15 WWTPs). Results revealed the presence of UV filters in 15 wastewater treatment plants in Catalonia (Spain) at concentrations ranging from 0.04 to 9.17 μg g⁻¹ dw.     

Effects of sewage sludge compost application on crops and cropland in a 3-year field study

Composted sewage sludge can be applied to cropland to supply nutrients and improve soil physical properties. However, farmers are much concerned about heavy metal accumulation in cropland and heavy metal availability for crops. A 3-year field study was carried out in this study to investigate the effects of sewage sludge compost (SSC) application on the heavy metal accumulation in cropland soil, rapeseed germination and plumelet development, and yields of barley and Chinese cabbage, compared with conventional mineral fertilization. In addition, the availability of heavy metals for barley and Chinese cabbage was examined. Experimental results showed that SSC application produced little effects on rapeseed germination and stimulated the rape plumelet development at lower application rates (<150 ton ha(-1)). Heavy metals (Cu and Zn) were accumulated in the topsoil (0-20 cm), the barley grains and the cabbage leaves. The yields of barley and Chinese cabbage generated positive response to the SSC application. Addition of mineral N-P-K fertilizers into SSC could further increase the crop yield. Considering the heavy metals accumulation in cropland soil and their availability for crops, SSC should be applied to cropland at a limited application rate (<150 ton ha(-1)).     

Biodegradation of nonylphenol in sewage sludge

We investigated the effects of various factors on the aerobic degradation of nonylphenol (NP) in sewage sludge. NP (5 mg/kg) degradation rate constants (k₁) calculated were 0.148 and 0.224 day⁻¹ for the batch experiment and the bioreactor experiment, respectively, and half-lives (t_1/2) were 4.7 and 3.1 days, respectively. The optimal pH value for NP degradation in sludge was 7.0 and the degradation rate was enhanced when the temperature was increased and when yeast extract (5 mg/l) and surfactants such as brij 30 or brij 35 (55 or 91 μM) were added. The addition of aluminum sulfate (200 mg/l) and hydrogen peroxide (1 mg/l) inhibited NP degradation within 28 days of incubation. Of the microorganism strains isolated from the sludge samples, we found that strain CT7 (identified as Bacillus sphaericus) manifested the best degrading ability.     

Bioremediation potential of a perchlorate-enriched sewage sludge consortium

The purpose of this work was to explore the reductive bioremediation potential of a perchlorate-enriched facultative anaerobic consortium. Rapid perchlorate reduction and bacterial growth were observed up to 1.84 g l(-1) of perchlorate, but not at 3.82 g l(-1) due to the toxicity. The specific growth rate of the mixed consortium was 0.1 h(-1). The consortium co-reduced perchlorate and nitrate with acetate as e- donor and carbon source. The presence of nitrate slowed down the perchlorate reduction rate. The other e- acceptors utilized include oxygen, chlorate, Cr(VI), and selenate. Over 95% of the 16 mg l(-1) of added Cr(VI) was reduced within 24 h of incubation with a high-density perchlorate-grown consortium. However, the consortium failed to couple growth with reduction of nitrite, sulfate, thiosulfate, and sulfite. During the search for autotrophic perchlorate reduction, many consortia from very diverse natural sources could not use sulfur compounds such as thiosulfate as e- donor.     

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.     

Pyrolytic characteristics of sewage sludge

In this study, a number of different sewage sludge including sludge samples from industrial and hospital wastewater treatment plants were characterized for pyrolysis behavior by means of thermogravimetric analysis up to 800 degrees C. According to the thermogravimetric results, five different types of mass loss behaviors were observed depending on the nature of the sludge used. Typical main decomposition steps occurred between 250 and 550 degrees C although some still decomposed at higher temperatures. The first group (Types I, II and III) was identified by main decomposition at approximately 300 degrees C and possible second reaction at higher temperature. Differences in the behavior may be due to different components in the sludge both quantitatively and qualitatively. The second group (Types IV and V), which rarely found, has unusual properties. DTG peaks were found at 293, 388 and 481 degrees C for Type IV and 255 and 397 degrees C for Type V. Kinetics of sludge decomposition can be described by either pseudo single or multicomponent overall models (PSOM or PMOM). The activation energy of the first reaction, corresponding to the main pyrolysis typically at 300 degrees C, was rather constant (between 68 and 77 kJ mol(-1)) while those of second and third reactions were varied in the range of 85-185 kJ mol(-1). The typical order of pyrolysis reaction was in the range of 1.1-2.1. The pyrolysis gases were composed of both saturated and unsaturated light hydrocarbons, carbon dioxide, ethanol and chloromethane. Most products, however, evolve at a quite similar temperature regardless of the sludge type.     

The importance of pathogenic organisms in sewage and sewage sludge.

Deficient sanitation poses a serious threat to human and animal health, involving complex relationships between environments, animals, refuse, food, pathogens, parasites, and man. However, by sanitizing and stabilizing the organic matter of sewage sludge, agriculture can utilize it to maintain soil, water, and air quality. As ingredients in soil amendments, such bioresidues are a source of nutrients for plants. Stabilization and sanitation of sewage sludge safely couple its recycling and disposal. This coupling becomes increasingly important as economic and environmental constraints make strategies for waste disposal more difficult to apply. The occurrence of viruses, bacteria, yeasts, fungi, and zooparasites in sewage sludge is reviewed in this article, and consequential epidemiologic concerns that arise from sewage sludge recycling is also addressed.     

Sorption of perfluoroalkyl substances in sewage sludge

The sorption behaviour of three perfluoroalkyl substances (PFASs) (perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonic acid (PFBS)) was studied in sewage sludge samples. Sorption isotherms were obtained by varying initial concentrations of PFOS, PFOA and PFBS. The maximum values of the sorption solid–liquid distribution coefficients (K_d,max) varied by almost two orders of magnitude among the target PFASs: 140–281 mL g^?1 for PFOS, 30–54 mL g^?1 for PFOA and 9–18 mL g^?1 for PFBS. Freundlich and linear fittings were appropriate for describing the sorption behaviour of PFASs in the sludge samples, and the derived K_F and K_d,linear parameters correlated well. The hydrophobicity of the PFASs was the key parameter that influenced their sorption in sewage sludge. Sorption parameters and log(K_OW) were correlated, and for PFOS (the most hydrophobic compound), pH and Ca?+?Mg status of the sludge controlled the variation in the sorption parameter values. Sorption reversibility was also tested from desorption isotherms, which were also linear. Desorption parameters were systematically higher than the corresponding sorption parameters (up to sixfold higher), thus indicating a significant degree of irreversible sorption, which decreased in the sequence PFOS?>?PFOA?>?PFBS.     

Settleability and dewaterability of sewage sludge with modified diatomite

Environmental Science and Pollution Research - In this study, cationic polyacrylamide (CPAM)-modified diatomite and cetyl&nbsp;trimethyl&nbsp;ammonium&nbsp;bromide (CTAB)-modified...     

Changes in sewage sludge carbon forms along a treatment stream

The behaviour and fate of macronutrients and pollutants in sewage sludge applied to the land are affected by the chemical composition of the sludge organic matter, which in turn is influenced by both sewage source and by sewage treatment processes. In this study, (13)C nuclear magnetic resonance (NMR) spectroscopy was used to characterise the organic matter of sludges collected at three different points along the treatment stream of a municipal sewage works with a domestic catchment. Sludge at the first point, an undigested liquid (UL) sludge, had a substantially different composition to the anaerobically digested (AD) and dewatered sludge cake (DC) materials, which were similar to each other. In particular, the UL sludge contained more alkyl C than the AD or DC sludges. All three sludges were found to contain mobile alkyl C that is poorly observed using the cross polarisation (CP) technique, necessitating the use of the less sensitive, but more quantitatively reliable direct polarisation (DP) technique to obtain accurate distributions of C types.     

施用城市污泥堆肥对土壤微生物群落结构变化的影响

在温室条件下进行了15周的盆栽实验,考察了施用城市污泥堆肥后,土壤中养分含量的变化规律,重点研究了施用城市污泥堆肥对土壤微生物群落结构变化的影响。实验发现,污泥堆肥能改善土壤养分,有机质和氮、磷含量得到显著提高。经PCR—DGGE分析,施肥1周后土壤中细菌和真菌的群落结构均发生了较大的变化。随着施肥时间的延长,细菌在富含有机质及氮、磷等养分的土壤环境下大量生长,多样性提高,其优势菌群属于γ变形菌、α变形菌和芽单胞菌;随着有机质的不断消耗,细菌的生长活性受到抑制,最终由于养分的缺乏,细菌种群多样性呈现小幅度的降低,优势菌群变为绿弯菌门、γ变形菌亚纲和厚壁菌门。对于真菌,其多样性指数在堆肥前3周逐渐提升,在第3～12周的监测中呈现相对稳定的变化趋势,优势菌群主要为座囊菌纲和散囊菌纲。     

施用城市污泥堆肥对土壤微生物群落结构变化的影响简

在温室条件下进行了15周的盆栽实验,考察了施用城市污泥堆肥后,土壤中养分含量的变化规律,重点研究了施用城市污泥堆肥对土壤微生物群落结构变化的影响。实验发现,污泥堆肥能改善土壤养分,有机质和氮、磷含量得到显著提高。经PCR-DGGE分析,施肥1周后土壤中细菌和真菌的群落结构均发生了较大的变化。随着施肥时间的延长,细菌在富含有机质及氮、磷等养分的土壤环境下大量生长,多样性提高,其优势菌群属于γ变形菌、α变形菌和芽单胞菌;随着有机质的不断消耗,细菌的生长活性受到抑制,最终由于养分的缺乏,细菌种群多样性呈现小幅度的降低,优势菌群变为绿弯菌门、γ变形菌亚纲和厚壁菌门。对于真菌,其多样性指数在堆肥前3周逐渐提升,在第3~12周的监测中呈现相对稳定的变化趋势,优势菌群主要为座囊菌纲和散囊菌纲。     

城市污水厂污泥的浸泡油炸

提出了一种利用餐厨废油为热交换介质,在常压下对城市污水厂污泥进行油炸干化制成固体燃料,以实现城镇两大废弃物一污泥和餐厨废油综合处置的方法。以大豆油模拟餐厨废油,研究了污泥油炸干燥特性及过程影响参数。实验结果表明,污泥经油炸干化后,干基含水率从初始的4．56kg／kg降低至0．05kg／kg,干基含油率升为0．37～0．47kg／kg,干污泥热值达到21．551～24．082MJ／kg,是一种高热值固体燃料。油温对污泥油炸干化过程影响显著,当油温从120℃升至180℃时,污泥干燥时间从28min缩短至4min。实验条件下,1t餐厨废油可处理约8．3t湿污泥。     

Modelling field-scale cadmium transport below the root zone of a sewage sludge amended soil in an arid region in Central Iran

Addition of trace metals such as cadmium to soils in metal-rich sewage sludge may result in contamination of soil and groundwater. This study addresses the plot-scale transport of Cd derived from sewage sludge in a layered clay soil in an arid region of central Iran. Sewage sludge was enriched by Cd at rates of 38 and 80 mg kg(-1) and applied to experimental soil plots using a complete random block design with three replicates. Cadmium concentration was measured as a function of depth after 185 and 617 days. HYDRUS-1D and MACRO codes were calibrated for Cd transport in the site treated with 80 mg kg(-1) sewage sludge. Model parameters were estimated by inverse modelling using the SUFI-2 procedure. The site treated with 38 mg kg(-1) cadmium was used to test the calibrated models. Both convection-dispersion equation (CDE) and non-equilibrium CDE in HYDRUS-1D produced reasonable calibration results. However, the estimated Freundlich sorption constants were significantly smaller than those measured in a batch study. A site tracer experiment revealed the existence of substantial macropore flow. For this reason we applied MACRO to account for this process. The calibration and test results with MACRO were as good as those obtained by HYDRUS-1D with the difference that adsorption constants were much closer to the measured ones. This indicates that in HYDRUS-1D, the adsorption parameters were underestimated in order to allow a deeper transport of Cd which had actually occurred due to macropore flow. A 20-year simulation scenario depicting the long-term effect of sludge application indicated small risk of groundwater contamination. However, high concentration of Cd near the soil surface raises a concern about the crop Cd uptake which should be further investigated.     

基于新型分层结构的污泥好氧堆肥处理

为了提高堆肥效率以及改进传统的堆肥方式,采用分层的堆置方式,以竹炭作为分隔材料,进行好氧堆肥实验,系统地分析了堆肥过程中常规理化特性的变化以及氮素损失情况。结果表明:木屑处理组(A)和竹炭处理组(B)中温度均经历了升温期、高温期以及降温期3个阶段,满足堆肥3阶段理论;以竹炭作为分层材料使高温期pH值降低至8.23,低于A组(8.98),而pH值的降低有利于控制氨气挥发;堆肥结束时,B组中DOC降解率为75.3%,明显高于A组(60.2%)。B组处理中氨气累积释放量为2 127.8 mg,小于A组的2 522.8 mg,可见竹炭作为堆体分隔材料对堆肥过程有机质的降解利用以及氨气挥发的控制均有一定的促进作用。