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.     

Initial organic matter transformation of soil amended with composted sewage sludge

 An incubation experiment with composted sewage sludge (CSS) just added to the soil was conducted to determine its initial effects on C decomposition, N nitrification and the transformation of organic matter. CSS was mixed with a sandy loam soil from uncultivated ochric epipedon of a Typic Haploxeralf at rates of 0, 40 and 80 t ha^–1 (dry weight). The data obtained showed that with regard to the unamended soil, both the 40 and the 80 t ha^–1 treatments produced the same result in decreasing respiratory activity, but the addition of increasing amounts of CSS progressively delayed C decomposition. The nitrification index (NI), defined as the relation between nitrate-N and nitrate-N + ammonium-N, increased in correlation with the C mineralization coefficient. Total organic matter decreased after incubation whereas the humic substances increased in relation to the total C mineralized. Received: 28 October 1999     

稻壳粉添加剂提高污泥的脱水效果研究

利用农业废弃物稻壳粉能有效提高污泥的脱水性能。该文研究了稻壳粉投加量对污泥脱水性能的影响及调理机理,同时分析稻壳粉调理对污泥滤液和脱水后污泥主要性质的影响,并进行技术经济分析。试验结果表明,稻壳粉的最佳投加量为70%污泥干质量(DS);在最佳调理条件下,与单独投加三氯化铁(FeCl_3,138.09g/kg)相比,污泥比阻降低了59.73%,污泥净产率提高了45.27%,污泥泥饼的含固率从13.99%提高到23.97%;扫描电镜结果表明,稻壳粉调理后的污泥泥饼具有不可压缩性和可渗透性,有利于污泥中水分的脱出;同时,稻壳粉的投加可有效降低滤液浊度和溶解性化学需氧量。因此,利用稻壳粉来调理污泥具有较大的潜力。     

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.     

Effects of municipal solid waste compost and sewage sludge on mineralization of soil organic matter

This work sets out to verify whether the application of municipal solid waste compost (MSWC) or treated urban sewage sludge (USS) organic amendments efficiently promote organic matter (OM) increases in a Haplic Podzol (PZha) and in a Calcic Vertisol (VRcc). For that purpose, carbon (C) mineralization and C kinetic parameters were studied, using a laboratory experimental incubation setup. The results showed that the addition of the amendments to the soils increased their mineralization capacities, and that the highest C mineralization rate was reached at the end of the first 2 d of incubation. The different characteristics of the soils seem to have influenced the C mineralization rates during the 28-d incubation. The USS induced higher C mineralization than the MSWC, and the PZha soil gave rise to higher C mineralization than VRcc. For all treatments, C mineralization adjusted well to an exponential plus linear kinetic model, suggesting that the organic C of the amendments was made up of two organic pools of differing degrees of stability. With the exception of the application of USS 60 t ha⁻¹, all the treatments increased the OM content on both soils, or at least the OM remained constant throughout the incubation.     

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.     

稻壳基生物炭对生菜Cd吸收及土壤养分的影响

探讨稻壳基生物炭对Cd污染土壤上叶菜吸收Cd和土壤Cd形态的影响作用,明确稻壳基生物炭对土壤Cd污染的调控效应,可为合理利用稻壳基生物炭降低叶菜Cd含量提供参考。采用盆栽试验,研究了稻壳基生物炭在不同用量水平下对2茬生菜地上部Cd含量、土壤养分含量及Cd赋存形态的影响。结果表明,在5~25 g-kg-1用量范围内,稻壳基生物炭显著降低了2茬生菜地上部和根系Cd含量,且在最大用量25 g-kg-1时效果最好,地上部Cd含量分别比未施稻壳基生物炭的对照处理降低了19.6%和45.8%,根系Cd含量分别降低了36.8%和28.0%。在25 g-kg-1用量水平下,稻壳基生物炭对土壤p H、有效磷、速效钾及有机质含量提升效果明显,但显著降低了土壤碱解氮含量。施加稻壳基生物炭对土壤有效态Cd含量及Cd化学形态也有不同影响。随着稻壳基生物炭用量的增加,土壤NH4OAc提取态Cd含量和弱酸提取态Cd含量显著降低,在用量为25 g-kg-1时,分别比对照降低17.9%和10.4%,可还原态Cd含量无显著变化,可氧化态Cd含量呈减低趋势,残渣态Cd含量增加17.6%。因此推测,提升土壤p H、降低土壤有效态Cd含量、增加残渣态Cd含量可能是稻壳基生物炭降低生菜体内Cd含量的主要原因。稻壳基生物炭可以作为土壤改良剂,抑制Cd污染土壤上叶菜对Cd的吸收,改善土壤养分状况。     

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.     

Effect of an artificial soil mix from coal fly ash and sewage sludge on soil microbial activity

An artificial soil mix was prepared from coal fly ash and sewage sludge and an experiment was performed to evaluate their effects on soil microbial respiration. Coal fly ash at 0%, 5%, 10%, 35% and 50% w/w was mixed with dewatered sewage sludge and then each ash-sludge mixture was incubated with a sandy soil at 1:1 v/v at 28°C for 42 days. All treatments showed the same carbon dioxide production pattern with a peak production at day 7 to day 14. Addition of ash-sludge mixtures to soil resulted in an increase in carbon dioxide production but the production rate decreased according to the ash amendment rate. The high pH of coal fly ash and the dilution effect of the sludge were the major reasons for the decrease. However, the ecological dose 50% values sharply increased from 26% at day 3 to 39% ash at day 14. This indicates the rapid acclimatization of microorganisms to the fly ash-sludge mixtures. Therefore, a brief stabilization period may be required for the establishment of soil microbial populations in soil amended with ash-sludge mixtures.     

施用辐照处理的污水污泥对作物产量和土壤氮的影响

A field experiment was conducted to study the feasibility of irradiated and non-irradiated sewage sludge as a fertilizer for the growth of wheat and rice. The irradiated and non-irradiated sewage sludge were applied at rates of 0 (CK), 75, 150, 225 and 300 kg N ha^-1 for wheat, and 0 (CK), 112.5, 225, 337.5 and 450 kg N ha^-1 for rice, respectively. (NH₄)₂SO₄ at a rate of 150 kg N ha^-1 for wheat, and 225 kg N ha^-1 for rice were added to the control treatments. Additionally, 20 kg ¹⁵N ha^-1 in the form of (NH₄)₂SO₄ was added to each treatment for wheat to study the effect of sewage sludge on chemical nitrogen fertilizer recovery. The results showed that the irradiation of sewage sludge by gamma ray at a dosage of 5 kGy increased crop yield by 11%~27% as compared to the non-irradiated treatments. Irradiation stimulated mineralization of organic nitrogen in the sludge and improved seedling growth. It was found that addition of irradiated sludge could reduce the leaching loss of chemical nitrogen fertilizer. Both irradiated and non-irradiated sewage sludge could increase the content of soil total nitrogen. Based on the preliminary results, it was concluded that irradiated sewage sludge could partly substitute for chemical nitrogen fertilizer in crop production.     

Effect of sewage sludge additions on Nocardia in soil

The population of Nocardia in soil under pasture increased 100 × over 14 months following the application of dried sewage sludge. Nocardia were isolated using selective media and on each of five samplings numbers of Nocardia in the control plots were very similar (

5.0 × 10³g^?1 dry weight), indicating both the reliability of the isolation technique, and that the steady increase in numbers of Nocardia was a real effect of dried sludge application. Amendment with wet sludge, which contains less organic matter did not have the same effect of stimulating growth of the soil population of Nocardia. On the basis of diagnostic tests and lipid analysis the organisms isolated all belong to the N. asteroides taxon. The potential benefits and hazards of inducing Nocardia population growth are discussed     

Leaching of heavy metals and nutrients from calcareous sandy‐loam soil receiving municipal solid sewage sludge

Leaching column experiments were conducted to determine the degree of mobility of heavy metals (HMs) and nutrients after the addition of municipal solid sewage sludge (MSS) in a sandy‐loam soil. Treatments were (1) soil application of low metal content MSS, (2) soil application of metal‐enriched municipal solid sewage sludge (EMSS), and (3) control. The MSS application represented a dose of 200 Mg dry weight (dw) ha^–1. Soil columns were incubated at room temperature for 15 d and were irrigated daily with distilled water to make a total of 557 mm. Leachates were collected and analyzed for HMs and nutrients. The Ni and Pb added to soil via MSS and EMSS were found to be leached through the 20 cm columns of calcareous sandy soil although Ni and Pb concentrations in the percolate were small relative to the total amounts of metals applied. Losses of K⁺ from the EMSS, MSS, and control were 92.5, 82.0, and 52.5 kg ha^–1, respectively. Losses of Mg²⁺ were in the range from 104.4 (control treatment) to 295.2 kg ha^–1 (EMSS), while the loss of Ca²⁺ was in the range from 265.0 (control treatment) to 568.2 kg ha^–1 (EMSS). The results showed that the amounts of P leached from EMSS (3.02 kg ha^–1) and MSS (2.97 kg^–1 ha^–1) were significantly larger than those from the control treatment (1.54 kg ha^–1). The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate‐limited dissolution of hydroxyapatite, β‐tri‐Ca phosphate, and octa‐Ca phosphate. The results indicate that application of MSS to a sandy soil, at the loading rate used in this study, may pose a risk in terms of groundwater contamination with Ni, Pb, and the studied nutrients.     

Growth and yield response of lettuce to irrigation and growth media from composted sawdust and rice husk

In sub-Saharan Africa, manure and loam soil are popular growing media substrates. However, their poor physiochemical properties limit their use in growing media. Following a survey of farmers, single species sawdust, mixed species sawdust, and rice husk (RH) were selected and composted with poultry manure. Additionally, the RH was charred for use in soilless media. Objectives were to produce feedstock-specific composts and determine appropriate proportion for using them in containerized systems. Three composts produced were amended with soil in ratios of 1:1, 1:2, and 1:3 (v/v) in an initial experiment. In a second experiment (soilless), the single sawdust and RH compost were each amended with RH biochar in ratios of 1:0, 1:1, 1:2 (v/v) and subjected to half or full pot irrigation. RH compost amended soils gave the highest lettuce yield. In the soilless media, 2:1 ratio (v/v) of biochar to sawdust compost gave the highest yield.     

Application of composted sewage sludges contaminated with heavy metals to an agricultural soil

To elucidate the mechanism of transfer of heavy metals into the food chain, an experiment was carried out with a calcareous soil, to which two different doses of a sewage sludge compost contaminated with either Cd or Zn, Cd, Cu, and Ni were applied. A crop of lettuce was then grown in the amended soils. The application of sewage sludge composts to a calcareous soil lowered the soil's pH, although the value was always around 8 at the end of the experiment. Electric conductivity rose with organic amendment. As anticipated, such an amendment improved the nutritional level of the soils, particularly Nand P, both total and available. Plant yields were negatively affected by organic amendments contaminated with heavy metals, the most dangerous in our experiment being Cd and Zn since this metals easily taken up by plants. As Ni and Cu form insoluble complexes with the organic matter of the sewage sludge composts they are not readily absorbed. Of the metals studied, Cd and Zn showed the highest bioavailability index.     

作物秸秆与城市污泥高温好氧堆肥产物对土壤氮矿化的影响

为揭示不同作物秸秆与污泥堆肥产物对土壤氮素矿化特征的影响,为科学施用城市污泥堆肥提供参考依据,通过室内培养试验研究了城市污泥与4种秸秆（小麦、水稻、玉米和油菜）高温好氧堆肥产物施入酸性紫色土、黄壤、石灰性紫色土后土壤氮矿化的差异。结果表明,4秸秆污泥堆肥均可显著提高3种土壤氮的潜在矿化势（N0）和矿化速度（k）,促进土壤氮的矿化,提高土壤NH4+-N、NO3--N质量分数,其中石灰性紫色土以油菜秸秆污泥堆肥和小麦秸秆污泥堆肥处理、黄壤以油菜秸秆污泥堆肥处理、酸性紫色土以小麦秸秆污泥堆肥处理提高幅度最大。作物秸秆与污泥堆肥施入土壤后,黄壤、酸性紫色土在培养60 d和30 d后趋于稳定,石灰性紫色土在培养60 d后仍有增高的趋势,但不同秸秆污泥堆肥对土壤氮矿化速度的影响无明显规律。结果说明秸秆污泥堆肥对土壤氮矿化的效应因土壤及秸秆类型的不同而异,根据研究结果提出了4种作物秸秆与城市污泥堆肥施用的建议。     

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.     

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].     

污泥堆肥和热干燥对土壤和土壤腐殖酸性质的影响

The effect of annual additions of composted sewage sludge (CS) and thermally dried sewage sludge (TS) at 80 t ha^-1 on soil chemical properties was investigated for three years in a field experiment under semiarid conditions. Humic acids (HAs) isolated by conventional procedures from CS, TS, and unamended (SO) and sludge amended soils were analysed for elemental (C, H, N, S and O) and acidic functional groups (carboxylic and phenolic) and by ultraviolet-visible, Fourier transform infrared and fluorescence spectroscopies. With respect to CS, TS had similar pH and total P and K contents, larger dry matter, total organic C, total N and C/N ratio and smaller ash content and electrical conductivity. Amendment with both CS and TS induced a number of modifications in soil properties, including an increase of pH, electrical conductivity, total organic C, total N, and available P. The CS-HA had greater O, total acidity, carboxyl, and phenolic OH group contents and smaller C and H contents than TS-HA. The CS-HA and TS-HA had larger N and S contents, smaller C, O and acidic functional group contents, and lower aromatic polycondensation and humification degrees than SO-HA. Amended soil-HAs showed C, H, N and S contents larger than SO-HA, suggesting that sludge HAs were partially incorporated into soil HAs. These effects were more evident with increasing number of sludge applications.     

Carbon mineralization in an arid soil amended with thermally-dried and composted sewage sludges

Soil amendment with sewage sludge (SS) from municipal wastewater treatment plants is nowadays a common practice for both increasing soil organic matter and nutrient contents and waste disposal. However, the application of organic amendments that are not sufficiently mature and stable may adversely affect soil properties. Composting and thermal drying are treatments designed to minimize these possible deleterious effects and to facilitate the use of SS as a soil organic amendment. In this work, an arid soil either unamended or amended with composted sewage sludge (CSS) or thermally-dried sewage sludge (TSS) was moistened to an equivalent of 60% soil water holding capacity and incubated for 60 days at 28 °C. The C–CO₂ emission from the samples was periodically measured in order to study C mineralization kinetics and evaluate the use of these SS as organic amendments. In all cases, C mineralization decreased after the first day. TSS-amended soil showed significantly higher mineralization rates than unamended and CSS-amended soils during the incubation period. The data of cumulative C–CO₂ released from unamended and SS-amended soils were fitted to six different kinetic models. A two simultaneous reactions model, which considers two organic pools with different degree of biodegradability, was found to be the most appropriate to describe C mineralization kinetics for all the soils. The parameters derived from this model suggested a larger presence of easily biodegradable compounds in TSS-amended soil than in CSS-amended soil, which in turn presented a C mineralization pattern very similar to that of the unamended soil. Furthermore, net mineralization coefficient and complementary mineralization coefficient were calculated from C mineralization data. The largest losses of C were measured for TSS-amended soil probably due to an extended microbial activity. The results obtained thus indicated that CSS is more efficient for increasing total organic C in arid soils.