Effects of sewage sludge amendment on soil aggregation

Sewage sludge in doses of 200 and 400 Mg ha⁻¹ (dry weight) were applied in an experimental rehabilitation of a limestone quarry to improve soil physical condition. The effect of this organic waste on soil aggregation and structural stability has been tested measuring aggregate size distribution by dry- and wet-sieving procedures over a period of 28 months. We discuss the influence of the organic components of aggregates on soil structure. The main effect of sewage sludge was to increase aggregate stability to raindrop impact (splash) just after application of the former but one year later this effect decreased notably. Organic matter is distributed in different ways between macro- and microaggregates, and this parameter seems to be responsible for the structure changes observed. Copyright © 1999 John Wiley & Sons, Ltd.     

Mutagenic potential of municipal sewage sludge amended soils

This study was conducted to measure the mutagenic potential of municipal sewage sludge amended soil. Two separate sludge samples were collected from one municipal wastewater treatment plant and applied to undisturbed soil lysimeters over a 9 mo interval. Soil and sludge samples were collected for approximately 2 yr following sludge application. Samples were solvent extracted using methylene chloride and methanol, and the bacterial mutagenicity of the resulting residue determined using the Salmonella/microsome assay. The maximum specific activity of the sludge amended soil was 416 net revertants per 10 mg of residue induced by the methanol fraction extracted from the Weswood soil collected 154 d following the first sludge application. In the Padina sand, the maximum specific activity was 320 net revertants per 10 mg of residue induced by the methanol fraction extracted from the sample collected 154 d following the first sludge application. The specific activity of the sludge amended soil was observed to decrease slowly with time. For both the Padina and the Weswood soils, mutagenic organic chemicals were detected in soil samples collected 510 d following the second sludge application. For the Weswood soil, the mutagenic activity per unit weight of soil with metabolic activation of the samples collected 510 d after the final sludge application was decreased by 15 and 76% for the methylene chloride and methanol fractions, respectively, when compared to the maximum weighted activity observed 56 d after the final sludge application. The results indicate that municipal sewage sludges may contain organic mutagens which are persistent in the soil.     

Vermicompost from municipal sewage sludge affects growth and mineral nutrition of winter rye (Secale cereale) plants

The aim of the study was to investigate sewage sludge vermicompost application effects on growth and mineral nutrition of winter rye (Secale cereale L.) plants as compared to two initial levels of mineral nutrient availability, pure sand and sand enriched with inorganic nutrients at the optimal level. Addition of sewage sludge vermicompost significantly inhibited rye seed germination at 20 to 50% sand substitution independently on mineral nutrient supplement. Growth inhibition was evident at early stages of plant development. However, at the later stages, sewage sludge vermicompost acted both as mineral fertilizer and plant growth-promoting agent. Significant stimulation of mineral uptake was seen only at high rates of vermicompost substitution (40 and 50%) already causing decrease in shoot dry matter accumulation. Vermicompost substitution resulted in a significant increase of leaf chlorophyll content. Beneficial effect of sewage sludge vermicompost in conditions of optimal mineral supply can result mainly from plant growth-promoting activity.     

Effect of composted sewage sludge amendment on soil nitrogen and phosphorus availability

Abstract

Municipal sewage sludge previously composted with sawdust (CSS) was applied to an eutric sandy cambisol at rates of 7.5, 15.0, 22.5, and 30 g#lbkg^‐1. Incubation and pot experiments were conducted to evaluate CSS effectiveness on nitrogen (N) and phosphorus (P) soil availability and on plant nutrition. The CSS rates did not increase soil mineral N and had little effect on organic P and on labile forms of P. Efficiency of total applied P was 17% for the soil labile forms and 4.8% for the resin extractable fraction. In contrast, CSS significantly increased hydroxide extractable inorganic P and nonextractable soil P fraction. The major portion of the increment on nonextractable forms was at the expense of HC1 extractable P fraction [calcium (Ca)‐bounded], dominant on the original CSS. Thus, chemical rather than biological reactions lead to the redistribution of CSS‐borne P to more firmly held forms after its application to the soil. Ryegrass dry matter yield, N content, and N uptake did not increase in CSS‐treated soils. Plant P content increased at the second harvest, but the effect was nil in the subsequent harvest. Total P uptake increased from 14.1 to 20.2 mg#lbpot^‐1, but percentage P recovery by ryegrass was modest, averaging 2.5% of the CSS‐borne P. Results suggest that moderate application of CSS to agricultural systems are inadequate for crop growth but may contribute to nutrient recycling without environmental risks related to N and P loss.     

Mudflat soil amendment by sewage sludge: Soil physicochemical properties,perennial ryegrass growth,and metal uptake

Abstract

The fast pace of cropland loss in China is causing alarm over food security and China’s ability to remain self-reliant in crop production. Mudflats after organic amendment can be an important alternative cropland in China. Land application of sewage sludge has become a popular organic amendment to croplands in many countries. Nevertheless, the land application of sludge to mudflats has received little attention. Therefore, the objective of the present work was to investigate the impact of sewage sludge amendment (SSA) at 0, 30, 75, 150 and 300 t ha^?1 rates on soil physicochemical properties, perennial ryegrass (Lolium perenne L.) growth and heavy metal accumulation in mudflat soil. The results showed that the application of sewage sludge increased organic matter (OM) content by 3.5-fold while reducing salinity by 76.3% at the 300 t ha^?1 rate as compared to unamended soil. The SSA reduced pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC) and contents of nitrogen (N), phosphorus (P), exchangeable potassium ions (K⁺), sodium ions (Na⁺), calcium ions (Ca²⁺) and magnesium ions (Mg²⁺) in comparison to unamended soil. There were 98.0, 146.6, 291.4 and 429.2% increases in fresh weight and 92.5, 132.4, 258.6 and 418.9% increases in dry weight of perennial ryegrass at 30, 75, 150, and 300 t ha^?1, respectively, relative to unamended soil. The SSA increased metal concentrations of aboveground and root parts of perennial ryegrass (p < 0.05). The metal concentrations in perennial ryegrass were Zn > Cr > Mn > Cu > Cd > Ni, and the metal concentrations in roots were significantly higher than aboveground parts. The metal accumulation in perennial ryegrass correlated positively with sludge application rates and available metal concentrations in mudflat soil. Land application of sewage sludge was proved to be an effective soil amendment that improved soil fertility and promoted perennial ryegrass growth in mudflat soil. However, heavy metal accumulation in plants may cause food safety concern.     

城市污泥专用复合肥在草皮生产中的应用

随着经济的发展,作为一个新兴的产业,我国的草皮生产业迅猛发展起来.但是与发达国家相比,我国的草皮生产及草坪建设仍存在着一系列的问题[1～3],其中草皮专用肥料品种很多,但良莠不齐[4,5].     

城市污泥的蚯蚓分解处理技术研究进展

城市污泥成分复杂,其中有机质、N、P、K含量丰富,Ca、Mg、Fe等矿物营养成分含量较高,此外还有许多重金属（Zn、Cu、Cd、Cr、Pb、Ni、Hg、As、Sn等）、有机有害成分以及病原菌。本文分析了国内外关于污泥处理处置的主要方法及其优缺点,重点讨论了一种新兴城市污泥处理技术,即城市污泥的蚯蚓分解处理技术（Vermicomposting）,利用蚯蚓处理城市污泥,不仅可以将污泥中的重金属富集于蚯蚓体内、去除病原菌、转移消化有机有害物,而且可将城市污泥转化为富含营养物质的有机肥,是一种无害化处理城市污泥的有效途径。最后,总结了目前城市污泥蚯蚓分解处理技术研究中存在的问题,并展望了其研究发展趋势。     

Response of tall fescue to composted sewage sludge used as a soil amendment

A pot experiment was conducted in the greenhouse to investigate the effects of composted sewage sludge as a soil amendment on growth and mineral composition of ‘Mustang’ tall fescue (Festuca arundinacea Schreb.). Three desert soils (loamy sand, sandy loam, clay) were amended with two different composted sewage sludges (city and county) at rates of 0, 7.5, 15, 30 and 60% by volume. Tall fescue was grown in the amended soils for four months. Growth rates, measured as harvested clippings, increased with sludge loading rate and also with clay content of the soil. Higher growth rates were maintained with the city as compared to the county sludge, although for both sources, growth declined for most treatments after nine weeks. Turf color ratings and percent N in the tissue increased with sludge loading rate and were highly correlated. Tissue analysis indicated a varied response between soil types.     

施用生活污泥改良滩涂土壤理化性状的探讨

采用符合土地改良用标准的生活污泥为材料,通过田间小区随机区组试验,研究了生活污泥的不同施用量（0、75、150、300、600 t/hm2）对滩涂土壤部分理化性质的影响。结果表明,施用生活污泥可显著改善滩涂土壤的理化性状。随着污泥施用量的提高,滩涂土壤的容重、密度、pH值逐渐下降,有机质、全氮、全磷、速效氮、速效磷、CEC均呈上升趋势,全钾、速效钾无显著变化。滩涂土壤的细菌、放线菌数量随污泥施用量的提高呈上升趋势。     

Effect of biosolids from municipal sewage sludge composted with rice husk on soil functionality

Two different biosolids were obtained composting anaerobic (A) and aerobic (B) municipal sewage sludge (SS) with rice husk. Higher amounts of SS (1:1 v/v) could be used in this composting process than in conventional ones. The two biosolids were characterized by chemical analysis and compared with a conventional green manure plus municipal solid waste and municipal SS compost. The effect of these products on soil functionality was studied in a 14-week incubation experiment by their addition to two different soils (silty clay—Ustic Endoaquert—and sandy loam—Aquic Xeropsamment). The total organic C ranged from 20 to 26 % and total N from 1.6 to 2.5 % in the two biosolids. The most relevant difference was due to dissolved organic C that was lower in the anaerobic biosolid (1 mg?C?kg^?1) than in the other products (5–6 mg?C?kg^?1). The total trace elements (Cd, Cr, Cu, Ni, Pb and Zn) contents were under the limits fixed by the European legislation for soil application of SS (EC Directive 86/278/EEC, 1986). The three biosolids did not show strong negative effects on soil functionality during the incubation experiment, although some significant differences were found. The aerobic biosolid B mainly increased cumulative N release, microbial activity, basal respiration rate, microbial biomass-C-to-total organic C ratio, β-glucosidase, alkaline phosphomonoesterase and aryl-sulphatase activities. The anaerobic one (B) decreased basal respiration rate, microbial biomass-C-to-total organic C ratio and aryl-sulphatase activity. DTPA soil bioavailable heavy metals were not affected by biosolids additions.     

Persistence of simazine and terbuthylazine in a semiarid soil after organic amendment with urban sewage sludge

The persistence of two herbicides, simazine and terbuthylazine, and appearance of their principal dealkylated chloro-s-triazine metabolites have been studied in agricultural soil after the addition of urban sewage sludge as organic amendment. Both herbicides and metabolites were monitored during long-term laboratory incubation (140 days) and analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). Residues were confirmed by gas chromatography with a mass selective detector (GC-MSD). A sonication microextraction method was used to extract the compounds. The organic amendments used were urban sewage sludge and the humic fraction of this sludge, to increase the organic matter content of the soil from 1% to 2%. For both compounds, simazine and terbuthylazine, the degradation began earlier in the amended soils. Simazine showed a higher dissipation rate than terbuthylazine, the percentage of the former at the end of the experiment being lower than 2% in all cases, while for terbuthylazine the corresponding percentage ranged from 5% to 46%. Organic amendment, mainly its humic fraction, caused a certain stabilization of terbuthylazine in the soil, but did not greatly influence the residual amount of simazine at the end of the experiment. The periodic aeration of the soil caused a greater degradation in the case of terbuthylazine. Only mono-deethylsimazine and deethylterbuthylazine were isolated from the soil during the time the experiment lasted, while the di-deethylated metabolite of simazine was not found.     

Impact of landspread sewage sludge and earthworm introduction on established earthworms and soil structure

Summary Sewage sludge was applied to twelve 4-m² plots in two forest (mixed hardwood, Norway spruce plantation) site and one old field site. The earthworm Eisenia fetida was introduced to half the control and half the treated plots. Earthworm populations were sampled by formalin extraction and hand-sorting five times in the year following treatment. One year after treatment, soil samples were wet-sieved and water-stable aggregate size-class arrays were determined.The dominant earthworm in the study site, Lumbricus terrestris, increased in density and mean individual biomass in response to sludge treatment in mixed hardwood and old field plots. In the Norway spruce plots, L. terrestris increased in individual biomass but decreased in density following sludge application. The density of the introduced E. fetida rapidly declined in all control plots. One year after introduction, E. fetida was found only in the sludge-treated Norway spruce plot. The introduction of E. fetida with sludge decreased the density and biomass of L. terrestris in the hardwood plots.Sludge treatment increased the percentages of 4-mm diameter water-stable aggregates in old field and hardwood plots. The addition of E. fetida with sludge in the hardwood plots generated no increase in 4-mm water-stable aggregates. In the old field, sludge + E. fetida increased the 4-mm water-stable aggregates. Little change in water-stable aggregates in response to either treatment combination was seen in the Norway spruce site.     

Characteristics of earthworms (Eisenia fetida) in PAHs contaminated soil amended with sewage sludge or vermicompost

Earthworms can be used to remove polycyclic aromatic hydrocarbons (PAHs) from soil, but this might affect their survival and they might accumulate the contaminants. Sterilized and unsterilized soil was contaminated with phenanthrene (Phen), anthracene (Anth) and benzo(a)pyrene (BaP), added with or without Eisenia fetida, sewage sludge or vermicompost. Survival, growth, cocoon formation and concentrations of PAHs in the earthworms were monitored for 70 days. Addition of sewage sludge to sterilized or unsterilized soil maintained the number of earthworms and their survival was 94%. The addition of sludge significantly increased the weight of earthworms 1.3 times compared to those kept in the unamended soil or in soil amended with vermicompost. The weight of earthworms was significantly lower in sterilized than in unsterilized soil. Cocoons were only detected when sewage sludge was added to unsterilized soil. A maximum concentration of 62.3 μg Phen kg⁻¹ was found in the earthworms kept in sterilized soil amended with vermicompost after 7 days and 22.3 μg Phen kg⁻¹ when kept in the unamended unsterilized soil after 14 days. Concentrations of Phen in the earthworms decreased thereafter and ≤2 μg kg⁻¹ after 28 days. A maximum Anth concentration of 82.5 μg kg⁻¹ was found in the earthworms kept in sterilized soil amended with vermicompost and 45.8 μg Anth kg⁻¹ when kept in the unamended unsterilized soil after 14 days. A maximum concentration of 316 μg BaP kg⁻¹ was found in the earthworms kept in sterilized soil amended with vermicompost after 56 days and 311 μg BaP kg⁻¹ when kept in the unsterilized soil amended with vermicompost after 28 days. The amount of BaP in the earthworm was generally largest after 28 days, but after 70 days still 60 μg kg⁻¹ was found in E. fetida when kept in the sterilized soil amended with sewage sludge. It was found that E. fetida survived in PAHs contaminated soil and accumulated only small amounts of the contaminants, but sewage sludge was required as food for its survival and cocoon production.     

Soil amendment with city sewage sludge increases soil extractable cadmium,nickel and zinc more than tannery,pharmaceutical and paper mill wastes

Abstract

The distribution of DTPA-extractable Cd, Ni and Zn in four profile samples collected from areas contaminated with wastes from tannery, city sewage, pharmaceutical and paper mills located at different places in Bangladesh was investigated. Soil samples were analysed for the total and their DTPA-extractable metal contents. The total concentration of metals in the soil horizons ranged from 0.07 to 0.62 mg kg^?1 for Cd, 31 to 54 mg kg^?1 for Ni and 59 to 838 mg kg^?1 for Zn, respectively. These metal concentrations were highest in the surface and lowest in the subsurface horizons. This trend was also observed for the DTPA-extractable amounts of these metals. The relative extractability, expressed as the ratio of DTPA to total contents (aqua regia-extractable) was 33 to 46% for Cd, 2 to 10% for Ni and 3 to 28% for Zn, respectively, in the A1 horizon, while in the B and C horizons the ratios decreased gradually as did total concentration, indicating that metal contamination was primarily limited to the surface horizon. For all three metals, the above mentioned ratio was highest in the city sewage soil and the lowest in the paper mill soil. In general, the extent of contamination among the profiles investigated was in the following order: city sewage>tannery>pharmaceutical>paper mill soil. Higher ratios of DTPA-extractable Cd, Ni and Zn in the city sewage soil than the other soils may create a risk for the contamination of agricultural products and ground water.     

Analysis of the genotoxicity of municipal sewage sludge extracts with sister chromatid exchange in cultured human lymphocytes

The genotoxicity of extracts of anaerobically digested sewage sludge to human cells was assessed by measuring the induction of sister chromatid exchanges in human peripheral lymphocytes with and without mammalian hepatic microsomal activation. A 2 hr exposure time with a total culture time of 76 hr was necessary to circumvent problems with cell cycle delays induced by the agents present in the extracts. With this modified procedure, the three extracts tested demonstrated a statistically significant increase in the number of sister chromatid exchanges/chromosome observed suggesting the presence of a genotoxic component in the sewage sludge.     

Soil biochemical activities and the geometric mean of enzyme activities after application of sewage sludge and sewage sludge biochar to soil

There is a need to improve the way in which wastes, such as sewage sludges, are managed and a potential way to proceed would be to transform them into biochar. On the other hand, there is a growing interest in the use of soil biochemical properties as indicators of soil quality because they are sensitive to alterations in soil management. Thus, we have studied the effect of a biochar obtained from sewage sludge on soil biochemical properties in an organic soil using two doses of biochar and comparing these results with the control soil and with soils amended with the same two doses of unpyrolyzed sewage sludge. Microbial biomass C, soil respiration, net N mineralization and several enzyme activities (dehydrogenase, β-glucosidase, phosphomoesterase and arylsulphatase) were monitored. The geometric mean of enzyme activities (GMea) was used as a soil quality index. Individual biochemical properties showed a different response to the treatments, while GMea showed an increase in the quality of soils amended with the high biochar dose and a decrease in those amended with a high sewage sludge dose. The geometric mean of enzyme activities was a suitable index to condense the whole set of soil enzyme values in a single numerical value, which was sensitive to management practices.     

The use of sewage sludge as soil amendment. The need for an ecotoxicological evaluation

Background, aim, and scope  Sewage sludge use in agriculture should be limited by the presence of metals and other persistent environmental pollutants. The present study aims to contribute for the definition of a test battery of ecotoxicological assays that allows a proper ecotoxicological characterization of sludges, providing information on their potential hazard and identified “safe” application levels. Materials and methods  Three sludges from distinct sources (urban, olive-processing, and electroplating industries) were tested using avoidance and reproduction tests with earthworms (Eisenia andrei) and springtails (Folsomia candida) and plant growth tests with turnips (Brassica rapa) and oats (Avena sativa). Different soil–sludge mixture concentrations mimicking recommended/realistic field dosages were tested. Results  Only the sludge from the electroplating industry induced an avoidance response from the earthworms (EC₅₀ = 0.4 t/ha) and collembolans (no observed effect concentration (NOEC) = 15 t/ha). This sludge was the only sludge responsible for any effect on the reproductive output of the earthworms (EC₅₀ = 7.74 t/ha). Regarding collembolans, none of the sludges tested caused any significant decrease in reproduction. In higher plant tests, the two industrial sludges were toxic, causing a decrease growth in both species. The EC₂₀ values determined for B. rapa were 20.3 and 24.2 t/ha and for A. sativa 14.7 and 16.2 t/ha for sludges from olive-processing and electroplating industries, respectively. Discussion  The metal loadings of the different test sludges could partially explain the results obtained. The toxicity of the test sludge from electroplating industry observed on the tested invertebrates and plants could be explained by the high amount of total chromium from which 22.3% was in the most toxic oxidation state—Cr(VI). However, the toxicity caused by the sludge from the olive-processing industry in the test plants could be attributed to the presence of other compounds (not measured in this study) since the metal content was not high enough to induce such an effect. The absence of toxicity showed by the urban test sludge was in agreement with its low levels of metals. Conclusions  The response of the different test organisms and end points varied according to the sludge type. The urban sludge was non-toxic whereas the sludge from the electroplating industry caused a toxic effect on almost all parameters measured (avoidance behavior of both test organisms, reproduction of earthworms, and growth of both plant species). Sludge from the olive-processing industry only caused a toxic effect on growth of both plant species. By analyzing the sensitivity of the different parameters for the most toxic sludge, it was found that avoidance and reproduction were more sensitive than plant growth, whereas plant seed germination was not sensitive at all. Recommendations and perspectives  The ecotoxicological evaluation of wastes can be used as an environmental safety control of sludge use in agriculture. A tiered approach could be adopted for this purpose, incorporating avoidance tests in the first tier (screening level) and reproduction and plant growth tests in a second tier. But more evidence aiming to define the most suitable ecotoxicological test battery for specific sludges with a different contamination profile is still needed.     

Survival of faecal indicators and enteroviruses in soil after land-spreading of municipal sewage sludge

One concern in regard to the spreading of sewage sludge is the potential for contamination of soil and water by pathogens present in sludge. We studied the survival of enteric micro-organisms in sewage sludge following direct land-spreading. The sludge produced by a wastewater treatment plant (capacity equivalent to 2000 inhabitants; sludge storage tank of 700 m³) was spread on a soil, at a rate of 80 m³/ha. The tested micro-organisms included three of specific sanitary interest: faecal indicators, spores of Clostridium perfringens and enteroviruses. The results highlighted three types of behaviour associated with these three groups of micro-organisms. The enteroviruses were not detected 2 weeks after spreading on the soil whereas the concentration of faecal indicators fell slowly with an observed decrease of between 1.2 and 1.8 logarithmic units over 2 months (but without the initial level of the soil being reached). Lastly, the concentrations of C. perfringens remained stable. The different survival times of the studied micro-organisms in soil, confirm the necessity to include several indicators (bacteria and viruses) to estimate reliably the sanitary risk related to sludge spreading.     

Effects of sewage sludge amendment on humic acids and microbiological properties of a semiarid Mediterranean soil

The residual effects of adding 40 t ha^–1 sewage sludge (SL) to a degraded soil cropped with barley were investigated after 9 and 36 months in a field experiment under semiarid conditions. The principal soil properties were apparently still affected by SL amendment 9 months after application but the effects disappeared after 36 months. With respect to control soil humic acids (HAs), the SL-HA was characterized by higher contents of S- and N-containing groups, smaller contents of acidic groups, a prevalent aliphaticity, extended molecular heterogeneity, and smaller degrees of aromatic polycondensation and humification. Amendment with SL caused an increase in N, H, S and aliphaticity contents and a decrease in C/N ratios and O and acidic functional group contents in soil HAs isolated 9 months after SL application. These effects tended to decrease after 36 months, most probably because the slightly humified SL-HA was mineralised over time through extended microbial oxidation, while only the most recalcitrant components such as S-containing and aromatic structures were partially accumulated by incorporation into soil HA. Microbial biomass, basal respiration, metabolic quotient and enzymatic activities increased in soil 9 months after SL application, possibly because of increased soil microbial metabolism and enhanced mineralisation processes. After 36 months these properties returned to values similar to those of the unamended soil, presumably due to the loss of energy sources.     

黄粉虫幼虫对城市污泥重金属的积累作用

室内采用正交试验设计进行4 因素多水平试验, 研究了温度、城市污泥和麦麸配比、饲养密度、幼虫体重对黄粉虫幼虫生长速度、死亡率以及幼虫重金属含量变化的影响, 探讨黄粉虫幼虫在城市污泥中的生长状况和对城市污泥重金属的积累作用。结果表明: 随着温度的升高, 幼虫生长率和死亡率都呈上升趋势, 饲养密度、污泥和麦麸配比对黄粉虫幼虫生长率、死亡率无显著影响; 15 ℃、密度为0.2 g·cm^-2、污泥/麸皮为1∶2、幼虫体重为85.4±5.9 mg 时, 幼虫对Cu、Se、Hg 的积累作用较显著; 15 ℃、密度为0.4 g·cm^-2、污泥/麸皮为1∶0、幼虫体重为85.4±5.9 mg 时, 黄粉虫幼虫对Cd 的积累能力显著; 20 ℃、密度为0.4 g·cm^-2、污泥/麸皮为1∶0、幼虫体重为34.9±4.9 mg 时, Zn 的积累系数较大; 黄粉虫幼虫对Cu、Cd、Se、Hg 和Zn 等重金属元素有很强的积累作用。