Long term effect of sewage sludge additions on populations of Nocardia asteroides,micromonospora and Thermoactinomyces in soil

Actinomycetes are considered to be members of the autochthonous component of the soil microflora. However, nocardiae and, to a lesser extent micromonosporae, can exhibit a sustained zymogenous-like response when complex recalcitrant organic substrates are added to soil in the form of dried sewage sludge. Numbers of Nocardia and Micromonospora do not increase when wet sludge, which contains less organic matter, is added to soil. In contrast, Thermoactinomyces did not follow this trend and greater numbers were isolated from the wet, rather than the dried, sludge plots. Results of herbage produced by the dried sludge plots indicate that plant nutrients were continually mineralized during the 3 yr following sludge addition.     

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.     

Effects of N-enriched sewage sludge on soil enzyme activities

Sewage sludge is increasingly used as an organic amendment to soil, especially to soil containing little organic matter. However, little is known about utility of this organic amendment with N-enriched or adjusted C:N ratios in soil. We studied the effects of adding of different doses (0, 100, 200 and 300 t ha⁻¹) and C:N ratios (3:1, 6:1 and 9:1) of sewage sludge on enzyme activities (β-glucosidase, alkaline phosphatase, arylsulphatase and urease) in a clay loam soil at 25 °C and 60% soil water holding capacity. Nitrogen was added in the form of (NH₄)₂ SO₄ solution to the sludge to reduce the C:N ratio from 9:1 to 6:1 and 3:1. The addition of different doses and C:N ratios of the sludge caused a rapid and significant in the enzymatic activities in soils, this increase was specially noticeable in soil treated with high doses of the sludge. In general, enzymatic activities in sludge-amended soils tended to decrease with the incubation time. All activities reached peak values at 30 days incubation and then gradually decreased up to 90 days of incubation. Sewage sludges also the increased available metal (Cu, Ni, Pb and Zn) contents in the soils. However, the presence of available soil metals due to the addition of the sludge at all doses and C:N ratios did negatively affect all enzymatic activities in the soils. This experiment indicated that all doses and C:N ratios of sewage sludge applied to soil would have harmful effects on enzymatic activity. Some heavy metals found in sewage sludge may negatively influence soil enzyme activities during the decomposition of the sludge.     

Role of soil properties in sewage sludge toxicity to soil collembolans

Soil properties are one of the most important factors explaining the different toxicity results found in different soils. Although there is knowledge about the role of soil properties on the toxicity of individual chemicals, not much is known about its relevance for sewage sludge amendments. In particular little is known about the effect of soil properties on the toxicity modulation of these complex wastes. In addition, in most studies on sewage sludges the identity of the main substances linked to the toxicity and the influence of soil properties on their bioavailability remains unknown.In this study, the toxicity of a sewage sludge to the soil collembolan Folsomia candida was assessed in nine natural soils from agricultural, grassland and woodland sites, together with the OECD soil. Correlations between the relative toxicity of sludge for collembolans in the different soils and their physical and chemical soil properties were assessed in order to identify the main compounds responsible for the effects observed. Furthermore, the relationships between the toxic effects to collembolans and water-soluble ions released by sludge, pH and electric conductivity were also assessed, together with the modulating effects of soil properties.Sludge toxicity was directly linked to the water extractable ammonium, which explained most of the mortality of the collembolans, and part of the inhibition of reproduction. For the last endpoint, nitrite also contributed significantly to the inhibition observed. The varied levels in water extractable ammonium in the different soils at equal dosages seem to be, in turn, modulated by some soil properties. Higher organic carbon contents were associated with lower toxicity of sludge, both for survival and reproduction, probably related to its higher ammonium sorption capacity. In addition, for reproduction, increasing the C/N ratio and pH appeared to increase the toxicity, probably due to both the greater difficultly in nitrification and the known unsuitability of alkaline soils for this species.     

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.     

The soil solution in a soil treated with digested sewage sludge

Toxic trace metals may percolate to the ground water from sewage sludge disposed onto land. Analyses are presented of the soil solution from a slightly acid loamy soil treated 7 years earlier with single applications of digested sewage sludge in amounts equivalent to 0, 150 & 330 t dry matter ha⁻¹
These very heavy dressings correspond to 2 & 4.5 times the recommended 30–year limit. Samples of soil and soil solution from four depths to 80 cm were analysed for Al, B, Ba, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, S, Sr, V, Zn, together with the OM of the soil, and the pH, alkalinity, dissolved organic carbon, and absorbance at 350 nm of the solutions.
These very heavy sludge applications were apparently still releasing substantial quantities of NO₃, and some SO₄ even after 7 years. Nitrate, SO₄, Mg, Ca, Sr, B, and possibly Ba are still moving through the profile, possibly to the ground water. Solution concentrations of Cu and Zn are considerably higher at all depths than those in the untreated plot, but they fall off sharply with depth. It is unlikely that any Cu or Zn is now reaching the ground water.
The paper also presents a set of published solution analyses for soils, sludge–treated soils and digested sludge, as a basis for further studies.     

Effect of the addition of sewage sludge as a fertilizer on a sandy vineyard soil

Purpose

The application of sludge from wastewater in agriculture has increased in recent years, and it is therefore important to assess the effect that such treatment has on both the soil and the plant. The aim of the study described here was to ascertain whether there is a variation in the properties of the soil and to determine if this addition has an impact on the plant.

Materials and methods

The area of investigation was close to the municipality of Villarrubia de los Ojos (Ciudad Real). In this work, six samples were taken from the surface horizon in the studied plot at a depth of 35 cm. A further three samples were taken: (i) a surface horizon of a soil close to the area under investigation but without treatment (control sample), (ii) a sample of sludge from the wastewater treatment plant and (iii) a sample of the mixture used by farmers as fertilizer. Laboratory tests were conducted in accordance with the SCS-USDA (1972) guidelines. Trace element samples were analysed by X-ray fluorescence spectrophotometry (Philips PW 2404).

Results and discussion

The parcel of land studied is dominated by a sandy texture (88.3 % sand), and a decrease in pH was observed in areas in which the mixture (manure + sludge) was added (pH?=?8.0) compared to areas in which fertilizer was not applied (pH?=?8.5). It was observed that the addition of the compound led to an increase in the electrical conductivity of the soil. The trace elements can be organized into two groups based on the results obtained in this study. One group contains the trace elements that were only present in the rows that were treated with the fertilizer. The other group of trace elements was mobilized throughout the whole plot.

Conclusions

The application of sewage sludge on agricultural soils can be very useful as an organic amendment because it produces an increase in soil organic matter. However, sewage sludge must be applied with caution due to the changes in soil chemical properties (for example, pH and E.C.). The use of this type of waste for prolonged periods of time can cause problems of contamination in the soil.

     

Influence of sewage sludge and heavy metals on nematodes in an arable soil

Summary The abundance of nematodes was investigated in agricultural plots treated in three different ways, the first with no treatment, the second with 300 m³ ha^-1 a^-1 raw sewage sludge and the third with 300 m³ ha^-1 a^-1 sewage sludge with the addition of heavy metals. The nematodes were determined down to the genus and were assigned to five feeding groups. Total nematode numbers were highest in the site treated with sewage sludge and heavy metals. The smallest total numbers were found in the control site. The plant-feeding nematode genera showed different patterns of abundance depending on the sludge treatment and heavy metal content. For the mycophagic and bacteriophagic nematodes, numbers increased with the amount of sludge, especially in the sites with a higher heavy metal content. The family Rhabditidae was the most numerous group in the sludge plus heavy metals treatment. In contrast to these findings, the omnivorous nematodes were very rare in the sludgetreated plots and were completely absent in plots treated with sludge plus heavy metals, whereas predatory nematodes were numerous only after the application of sludge alone.     

Microbiological processes in gray forest soil treated with sewage sludge compost

The effect of compost made of sewage sludge and applied in dose up to 90 t/ha on the microbial biomass, soil respiration, nitrogen-fixing activity, and on the organic matter content and concentrations of toxic metals in the gray forest soil of a nursery forest garden was studied in a field experiment. It was found that the adverse effects of the compost components on the studied parameters of the microbial communities were not observed two years after the compost application; this fact suggested that the soil microbial community overcame the stress caused by this anthropogenic impact.     

The use of bioassays for evaluating the toxicity of sewage sludge and sewage sludge-amended soil

Background and Aims  

In soils, the most commonly mentioned hazardous substances are metals. One of the sources of its accumulation is the application of sewage sludge. However, little information is available regarding the estimation of the toxicity of sewage sludge or soil treated with sewage sludge, even by means of a battery of bioassays. In this study an evaluation of a battery of bioassays was carried out for toxicity assessment of sewage sludge and sewage sludge-treated soil. The objectives of this study were a) to compare the sensitivity of the different bioassays for the toxicity determination of sewage sludge contaminated with metals and soil treated with this sewage sludge, b) to elaborate a procedure for the attribution of sewage sludge samples to hazard classes based on the ecotoxicological data, and c) to evaluate the suitability of elutriate bioassays and microbial toxicity tests for the assessment of sewage sludge-treated soil.     

污泥土地利用研究：Ⅲ、富锌污泥

西通过温室盆栽试验方法研究不同富锌污泥施用方法对水稻生长及其重金属含量的影响，结果表明，污泥施用主要通过增加水稻分蘖来促进水稻生长从而提高产量。污泥的施用显提高了水稻茎叶和籽粒中锌的含量。     

Long-term exposure to Zn-spiked sewage sludge alters soil community structure

An 8 year study to investigate the effects of Zn-spiked sewage sludge additions on the microbial community structure and microbial processes was carried out in a field soil under pasture. The microbial community structure was evaluated using a combination of multiplex-terminal restriction fragment length polymorphism (M-TRFLP) and T-RFLP fingerprinting approaches. Soil respiration, microbial biomass and enzymatic activities were measured as indicators of soil microbial processes. Changes in the microbial community structure, with Zn additions were evident in all the microbial groups investigated (bacteria, fungi, archaea, actinobacteria and rhizobia/agrobacteria). The fungal community showed the greatest response to Zn additions compared to the other microbial communities measured. The relative abundance of several fungal terminal restriction fragments (TRFs) significantly increased in high Zn treated treatments, at the expense of others, some of which were lost from T-RFLP profiles completely. These results indicate that metal-spiked sludge application can have long-lasting impacts on the composition of the microbial community in pasture soils. Despite notable changes in community structure there was no significant long-term impact of Zn-spiked sludge applications on microbial respiration, biomass or enzyme activities.     

Effect of sewage sludge on suppressiveness to soil-borne plant pathogens

The objective of this study was to evaluate the effect of sewage sludge on soil suppressiveness to the pathogens Fusarium oxysporum f. sp. lycopersici on tomato, Sclerotium rolfsii on bean, Sclerotinia sclerotiorum on tomato, Rhizoctonia solani on radish, Pythium spp. on cucumber, and Ralstonia solanacearum on tomato. Soil samples were collected from an experimental corn field in which sewage sludge had been incorporated once a year, since 1999. Sludge from two sewage treatment stations in Brazil (Franca and Barueri, SP) were applied at the rates of one (1N), two (2N), four (4N) and eight (8N) times the N recommended doses for the corn crop. Soil suppressiveness was evaluated by methods using indicator host plants, baits and mycelial growth. There was no effect of sewage sludge on soil suppressiveness to Fusarium oxysporum f. sp. lycopersici in tomato plants. For S. rolfsii, reduction of the disease in bean was inversely proportional to the dose of Franca sludge. The incidence of dead plants, caused by S. sclerotiorum, was directly proportional to sludge doses applied. For R. solani and R. solanacearum, there was a linear trend with reduction in plant death in soils treated with increasing amounts of sludge from Franca. There was an increase in the pathogen community of Pythium spp., proportional to the amounts of sewage applied. The effects of sewage sludge varied depending on the pathogen, methodology applied and on the time interval between the sewage sludge incorporation and soil sampling.     

Long-term effects of farmyard manure and sewage sludge on some soil biochemical characteristics

 Changes in some soil biochemical properties were investigated following repeated applications of aerobically digested sewage sludge (SS) under field conditions over 12 years, and compared with those of an adjacent soil cultivated and amended with 5 t ha^–1 year^–1 (dry weight) farmyard manure (FYM) for at least 40 years, as well as with those of an adjacent uncultivated soil, in order to ascertain changes in soil quality. A short-term aerobic incubation was used to determine the potential of the samples to mineralize the organic C supplied. Results indicated that cultivation caused a reduction in total, humified and potentially mineralizable organic C, total N, light-fraction (LF) C, total and water-soluble carbohydrates, phenolic compounds, cation-exchange capacity (CEC), microbial biomass C, specific respiration, hydrolytic and urease activities, and an increase in the heavy metal content. Total and water-soluble carbohydrates and phenolic compounds expressed as a percentage of total organic C (TOC) were similar in the differently managed plots. Of the two amendments, FYM treatments showed higher amounts of TOC and N, LF-C, total and water-soluble carbohydrates, phenolic substances, CEC, specific respiration of biomass, hydrolytic and urease activities, similar amounts and characteristics of humified organic matter and lower concentrations of Cu, Zn and Cr. Both FYM and SS were inadequate treatments for the restoration of soil organic matter lost as a consequence of cultivation. Received: 20 October 1998     

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     

Effect of the earthworm, eisenia foetida (oligochaeta), on fluxes of volatile carbon and sulfur compounds from sewage sludge

Rates of decomposition, measured by flux rates of CO₂, O₂ CH₄, H₂S, CH₃SH and (CH₃)₂S, and populations of anaerobic bacteria were determined in an activated sludge before and after ingestion by Eisenia foetida. Feces always exhibited higher (P < 0.05) fluxes of CO₂ and O₂ and generally lower (P < 0.05) fluxes of CH₄, H₂S, CH₃SH and (CH₃)₂S than sludge, indicating that E. foetida feeding stimulated aerobic decomposition. For both sludge and feces, decreasing moisture contents resulted in lowered CO₂ and O₂ flux rates. Volatile sulfur compounds produced over 24 days accounted for only 0.02–0.08% of the total S present.Populations of total anaerobes, nitrate reducers, sulfate reducers and methanogens were not significantly affected by either earthworm feeding or moisture content.     

Changes in the structure of fungal communities of soil treated with sewage sludge

The influence of a single addition of sewage sludges to soils on the composition of fungal communities, soil pH (physical factor) and presence of Eschericha coli (sanitary factor) during 1 year was studied. Only the pH of soil treated with limed sewage sludge increased significantly from 7.01 to 7.58 after 3 months. E. coli was still present in soil 1 year after application of sewage sludge. Fungal numbers increased in the sewage-sludge-treated soil up to 6 months after application (maximum value was 7.5 times that of the control) and then decreased to reach values comparable to those of the control. Treated soils showed different fungal communities to the control with presence of keratinolytic fungi (Sporothrix schenckii, Microsporum sp.), yeasts (Geotrichum candidum, Candida sp., Rhodotorula sp. Cryptococcus sp.), and other potential pathogenic fungi (Aspergillus niger, Fusarium solani). The results indicate that fungi belonging to the genus Candida could be used as specific indicator organisms of the sanitary condition of soils treated with sewage sludge.     

Effects of the application of heated sewage sludge on soil nutrient supply to plants

Abstract

We previously reported that heating sewage sludge significantly changes the rate of N mineralization. The present study was undertaken to examine the extent to which these changes affect plant growth and nutrient supply after application to different soils. A pot experiment in which komatsuna plants (Brassica campestris L. var. rapa) were grown in a Fluvisol or an Arenosol indicated that the amount of N taken up by the plants increased significantly by heating air-dried sludge at 120°C and decreased significantly by heating at 180°C. Heat-drying of the sludge at 120°C or 180°C also increased the N uptake significantly. These plant responses could be explained by the heat-induced changes in the release of inorganic N from the sludge. In contrast to N, the sludge materials containing Fe as a coagulant immobilized soil soluble P. When the sludge was applied to an Andosol, the N-supplying effects on plant growth were offset by P adsorption onto the sludge and soil. In a successive pot experiment conducted without additional sludge application, it was further suggested that frequent sludge application is required to maintain plant growth. However, it will also lead to the accumulation of sludge components in the soil because less than 40% and 15% of the sludge N and P, respectively, were apparently recovered in two harvests of the plants. In conclusion, heated sludge materials can act as an effective organic N fertilizer provided that they are applied to a suitable soil and that the short-term effects on soil productivity are balanced with the long-term effects on environmental quality.     

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.