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.     

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。     

污泥土地利用研究：—Ⅴ．高铜污泥

本采用田间小区试验方法研究了高铜污泥对辣椒生长、Vc含量和重金属含量的影响。结果表明，污泥施用量在3．75和7．5t/hm^时，辣椒各个生长指标都有所增加，有些指标都有所增加，有些指标甚至优于施用化肥处理。污泥施用对辣椒果实Vc含量没有明显降低的趋势，污泥施用未显地增加辣椒植株和果实对铜、锌、镉和镍的吸收。     

Modification of soil porosity after application of sewage sludge

The effect of the application of sewage sludge on soil porosity over 28 months is discussed here. Anaerobic sludges of urban refuse waters were applied on a degraded limestone soil in a mining land by two ways. First, a previous mixture of sludge and soil was carried out; this was then applied to the target land. Second, a direct application of sludge to soil and tilling. Porosity and pore morphology were measured on thin sections prepared from undisturbed soil samples. Data were obtained from backscattered electron images and image-processing computer equipment. The application of sludge induced an increase of both soil fine microporosity (φ<50 μm) and coarse microporosity (φ>50 μm). However, this effect showed transient, since no significant differences were reported in relation to the control plot after one year from application. The incorporation of sludge and developed vegetation modified coarse micropore irregularity and orientation. On the other hand, fine micropore morphology remains unchanged.     

污泥土地利用研究：Ⅱ、连续化学提取法研究施污泥土壤重金属的有效性和环境风险

本文采用连续化学提取法研究了施用污泥土壤中重金属的形态分配及有效性。铜和在2种土壤上施用污泥前、后的形态分配都有所差异，铜在 湖相水稻土上可以氧化态为主：红壤性水稻土可氧化态和可还原态含量都较高。锌在河湖相水稻土以可还原态为主，在红壤性水稻土以醋酸溶解态为主，两种土壤上，铜和锌的3种不同形态含量与污泥施用量之间都有很好的相关性，连续提取对于研究重金属的形态分配比单独提取更有价值。     

污泥土地利用研究：Ⅳ、无锡污泥与香港碱化污泥的肥效比较

本通过盆栽试验研究了污泥施用对青菜和番茄生长的影响，试验表明，污泥施用可显促进青菜和番茄的生长，但和长在酸酸性红壤和太源水稻土上两种蔬菜对污泥施用的响应不同，香港碱性污泥产品对青菜在酸性红壤上的增产效果优于无锡污染；无锡污泥随施用量增加产量有所增加：太湖水稻土上无锡污泥的肥效优于香港碱性污泥产品。污泥施用不仅对当茬蔬菜增产明显，对后茬蔬菜也有增产效应。     

Major nutrients,heavy metals and PBDEs in soils after long-term sewage sludge application

Purpose

Two contrasting soils receiving long-term application of commercial sewage sludge fertilizers in China were investigated to determine the concentrations of selected nutrients, heavy metals (HMs) and polybrominated diphenyl ethers (PBDEs) present to evaluate the impact of sewage sludge fertilizer on soil fertility and environmental risk.

Materials and methods

Soil samples were collected from Tangshan City, Hebei province and Ningbo City, Zhejiang province and divided into two portions, one of which was air-dried and sieved through 2-, 0.25- and 0.149-mm nylon mesh for determination of nutrients and heavy metals. The other portion was frozen at ?20°C, freeze-dried and sieved through 2-mm nylon mesh for PBDE analysis. The concentrations of nutrients, heavy metals and PBDEs were determined in all samples.

Results and discussion

Concentrations of nutrients and heavy metals in soils amended with low rates of sewage sludge fertilizer (SSF) and conventional fertilizer were compared. After long-term excessive amendment with SSF from Ningbo City (SSF-N), the concentrations of soil total N, P, aqua regia-extractable HMs and DTPA extractable HMs were higher than the control, especially in the arable layer. Moreover, the concentration of aqua regia-extractable Zn (457 mg kg^?1) exceeded the recommended China Environmental Quality Standard for soils (GB15618-1995). All 8 target PBDE congeners were found in fertilizer SSF-N and soil with excessive amendment with SSF-N for 12 years, but the concentrations of 8 different PBDEs in SSF-N-amended soil were not significantly different from control soil.

Conclusions

Both economic and environmental benefits can be obtained by careful application of sewage sludge fertilizer to recycle plant nutrients. Repeated and excessive application rates of sewage sludge fertilizer may pose environmental risk, especially in respect of soil heavy metal and PBDE contamination, and high concentrations of phosphorus may also be environmentally detrimental.

     

Effects of sewage sludge application method on corn production

Abstract

A study was conducted to determine the effects of land application of municipal sewage sludge to agricultural land in Upper Cumberland Region of the Tennessee valley. Treatments included single and annual applications of sewage sludge both surface applied and injected into the soil. The primary objective of the study was to determine the effects of different land application methods of sewage sludge on corn grain yields. Other objectives were to determine the plant availability and migration of sludge Cu and Zn, and to determine organic N mineralization rates based on corn yield and leaf N content. Application of sewage sludge positively affected corn grain yields due to increased availability of N, and in drought years soil moisture. Yield and leaf N content data suggest that organic N mineralization rates near 50% in the year of application and 30% in the second year. Application of sewage sludge resulted in a greater increase in availability of Cu at the soil surface as compared to Zn, however neither Cu or Zn leached from the surface of the soil.     

Effects of sewage sludge stabilization on fertilizer value and greenhouse gas emissions after soil application

Application of sewage sludge on agricultural land becomes more and more common in many parts of the world in order to recycle the nutrients from the sludge. A range of sewage sludge stabilization techniques are available to make the sludge more stable prior to storage, transportation, and application. These stabilization techniques include dewatering, drying, anaerobic digestion, composting, and reed bed sludge treatment. However, very few studies have investigated the effect of these techniques after the sludge has been applied to agricultural land. The objective of the current study was therefore to investigate the effect of sewage sludge stabilization techniques on the C and N mineralization and gaseous emissions from soil. A soil incubation was conducted to determine the rate of C and N mineralization and N₂O and CH₄ emissions of sewage sludge stabilized using different techniques. Unstabilized sludge released up to 90% of their C content as CO₂, part of which could be caused by release of CO₂ from carbonates. Compared with this, sludge stabilization including anaerobic digestion and drying resulted in a reduction of the C mineralization rate of about 40%. Liming reduced C mineralization with around 29%, while treatment in a reed bed system reduced it by 74%. The current study thus clearly demonstrated that stabilization techniques resulted in sludge that was more stable once they were applied to agricultural land. Stabilization also reduced the N immobilization phase, potentially improving the value of the sludge as a fertilizer. Emissions of CH₄ were also reduced through sludge stabilization and mainly occurred after application of easily degradable sludge types, which is likely to have enhanced the creation of anaerobic microsites. The stabilization processes also decreased emissions of N₂O. The results for both CH₄ and N₂O indicate that the stabilization tends to reduce the chance of developing conditions where these gases could be produced.     

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].     

Bacterial leaching of heavy metals from sewage sludge for agricultural application

Bacterial leaching of heavy metals from sewage sludge was studied to assess the potential of agricultural application of the decontaminated sludge. Experiments were conducted in both batch processes (at 28 ?C) and continuous process (at 30 ?C) using a culture of Thiobacillus ferrooxidans and a mixted culture of Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Reagent grade ferrous sulfate, spent ferrous sulfate and pyrite were used as the energy substrates. A first order kinetic model of Cu solubilization was proposed. It was shown that the processes in the continuously stirred tank reactor (CSTR) and the air lift reactor (ALR) with 20% cell recycling were more efficient than the others for metal solubilization due to a relatively large bacterial population.     

Comparison of phosphorus availability with application of sewage sludge,sludge compost,and manure compost

Abstract

The objectives were to determine if phosphorus (P) from different organic wastes differs in availability to crops. Four materials: digested, dewatered sewage sludge (DSS); irradiated sewage sludge (DISS); irradiated and composted sewage sludge (DICSS); and composted livestock manure (CLM) were applied for two years at five rates (0, 10, 20, 30, 40 Mg#lbha^‐1#lbyr^‐1) with four replicates. Uptake of P was measured in lettuce [Lactuca saliva L. (cv. Grand Rapids)], bean [Phaseolus vulgaris L. (cv. Tender Green)], and petunia [Petunia hybrida Vilm. (cv. Superior Red)] in 1990, and in consecutively harvested two cuts of lettuce in 1991. Percentage of total P that was extractable by 0.5M sodium bicarbonate (NaHCO₃) in CLM (30–70%) was much higher than in DSS, DISS, and DICSS (0.8–5.6%). Phosphorus uptake by crops harvested in an early stage of growth, lettuce in 1990 and first cut lettuce in 1991, and the extractable soil P linearly increased with total P applied. The lack of response in P uptake with bean pod and petunia in 1990, and the second cut lettuce in 1991, was possibly due to their advanced stage of maturity. Much larger amounts of P were applied with DSS, DISS, and DICSS than with CLM, while P uptake and extractable soil P did not increase compared to that in the treatment that received no P. The low availability of P in sludge was likely caused by iron (Fe) and aluminum (Al) which precipitated P. Sludge irradiation and/or composting had no significant effect on P availability.     

污泥土地施用研究I.施用污泥土壤中重金属的化学浸提性研究

本研究了施用污泥的太湖水稻土和江西第四纪红壤性水稻土中重金属的化学提取性。结果表明，随着污泥施用量的增加，土壤中Ｃｕ，Ｚｎ，Ｃｄ的醋酸，醋酸铵，ＥＤＴＡ３种提取形态的浓度都明显增加，有很好的相关性，各提取态浓度在各施用量之间存在显差异。污泥施用没有增加Ｐｂ含量，这可能与污泥本身含Ｐｂ量低有关。     

Effects of sewage sludge disposal

The disposal of sewage sludge affects the environment as the sludge May, contain harmful components such as pathogenic organisms, organic compounds, heavy metals and excess phosphorus and nitrogen. Depending on the method of disposal, these effects can be immediate or time-delayed and non-linear. the effects of dumped or landfilled sewage sludge can be characterized through its leaching capability, which depends on the treatment before dumping. Treatment May, be simple dewatering or advanced incineration, wet oxidation or immobilization. Leach-ability is considered here.     

Soil amendment with municipal sewage sludge affects the immune system of earthworms Dendrobaena veneta

Dendrobaena veneta is an earthworm species capable of consuming a wide range of organic wastes which may be used as a field indicator of municipal sewage sludge applied to land. The aim of the present 8-week laboratory experiment was to check viability, reproduction and the immune system of D. veneta maintained in soil without food additions (control 0s group) or in soil amended with 25% or 50% municipal sewage sludge (25s and 50s groups, respectively). Reproduction and immunity are important physiological functions whose detailed study can provide information on the effects of pollutants. After the 8-week exposure period, earthworm mortality (2 out 20 individuals) was recorded only in the 50s group. Reproduction was high in the 25s group (44 cocoons and 41 juveniles) whereas reproduction was almost completely inhibited both in the food-deprived control 0s group (1 cocoon, 3 juveniles) and in the 50s group containing a high amount of sludge (2 cocoons). Significantly increased numbers of non-invasively extruded coelomocytes were recorded 3 weeks after the start of the experiment in the 50s group, but they dropped to the food-deprived control level by the end of 8 weeks likely due to exhaustion of the immune system coping with sludge-derived microbes and/or toxins. In contrast, numbers of coelomocytes in the 25s group increased gradually reaching the maximum at the end of the experiments. In conclusion, high amounts of municipal sewage sludge are detrimental to worms, inhibiting reproduction and inflicting mortality. A moderate amount of municipal sewage sludge provides a good source of nutrients for D. veneta, supporting their growth and reproduction for at least 8 weeks. Immunological parameters might serve as useful indicators of earthworm exposure to sewage sludge.     

Temporal response of soil biochemical properties in a pastoral soil after cultivation following high application rates of undigested sewage sludge

Soil biochemical properties were measured annually between 1995 and 1999 in soil from an 8-ha site that had received over 1,000 wet tonnes ha^–1 undigested sewage sludge, 1–4 years earlier. Basal respiration generally declined with time and was usually greatest in the untreated control area. This trend was attributed to a similar trend in soil moisture content. In contrast, microbial biomass C increased with time and also generally increased with sludge treatment age. Microbial biomass C, and to a lesser extent sulphatase activity, accurately predicted the order of sludge application to the site. This was perceived as a function of time since tillage and pasture establishment, with activities increasing in parallel to the build up of C residues in the soil, and not an effect of sludge or its composition. Except immediately after sludge application, there was no effect on N mineralisation and nitrification. None of the biochemical properties was strongly correlated with heavy metal concentrations. Our results suggest that there was little effect on soil biochemical properties, either adverse or beneficial, of adding raw sewage sludge to this site. Although a companion study showed considerable mobility and plant uptake of heavy metals, this difference could mainly be attributed to a different sampling strategy and the effects of intensive liming of the site.     

Medically used radionuclides in sewage sludge

The concentration of medically used radionuclides has been studied in sludge from the sewage treatment plant serving the borough of Malmo. In this area all nuclear medicine procedures are carried out in one hospital and almost all patients live in the borough. Therefore, the input of medically used radionuclides into the sewage system can be estimated with good accuracy. Samples of digested sludge have been taken once or twice a week during half a year. Iodine-131 (physical half life (T) = R.05 d) was detected in all samples. The ¹³¹I-activity concentration due to medical use varied between (0.03±0.01) and (0.12±0.02) nCi kg^?1. The ratio between the total output of ¹³¹I via the sludge and an adherent input of the radionuclide into the sewage system was determined to (2.6 ± 0.6) × 10^?3, which is equivalent to a ratio of (2 ± 1) × 10^?2 for stable I. Occasionally measurable activities of ¹⁹⁸Au (T=2.7 d) and ²⁰¹T1(T=3.l d) have been found. The radioactivity concentration of medically used radionuclides in the sludge is low and constitutes no health problems for the persons involved. The sludge however has proved to be a very sensitive and suitable integrator of radioactive material released from a large urban area.     

Soil phosphorus dynamics and phytoavailability from sewage sludge at different stages in a treatment stream

The effect of different stages of sewage sludge treatment on phosphorus (P) dynamics in amended soils was determined using samples of undigested liquid (UL), anaerobically digested liquid (AD) and dewatered anaerobically digested (DC) sludge. Sludges were taken from three points in the same treatment stream and applied to a sandy loam soil in field-based mesocosms at 4, 8 and 16 t ha⁻¹ dry solids. Mesocosms were sown with perennial ryegrass (Lolium perenne cv. Melle), and the sward was harvested after 35 and 70 days to determine yield and foliar P concentration. Soils were also sampled during this period to measure P transformations and the activities of acid phosphomonoesterase and phosphodiesterase. Data show that the AD amended soils had the greatest plant-available and foliar P content up to the second harvest, but the UL amended soils had the greatest enzyme activity. Characterisation of control and 16 t ha⁻¹ soils and sludge using solution ³¹P nuclear magnetic resonance (NMR) spectroscopy after NaOH–EDTA extraction revealed that P was predominantly in the inorganic pool in all three sludge samples, with the highest proportion (of the total extracted P) as inorganic P in the anaerobically digested liquid sludge. After sludge incorporation, P was immobilised to organic species. The majority of organic P was in monoester-P forms, while the remainder of organic P (diester P and phosphonate P) was more susceptible to transformations through time and showed variation with sludge type. These results show that application of sewage sludge at rates as low as 4 t ha⁻¹ can have a significant nutritional benefit to ryegrass over an initial 35-day growth and subsequent 35-day re-growth periods. Differences in P transformation, and hence nutritional benefit, between sludge types were evident throughout the experiment. Thus, differences in sludge treatment process alter the edaphic mineralisation characteristics of biosolids derived from the same source material.     

Environmental evaluation of sewage sludge application to reclaim limestone quarries wastes as soil amendments

Restoration of degraded soils with organic wastes could be a feasible practice to minimize erosion in the Mediterranean area, but with the risk of soil and groundwater pollution. Currently the use of sewage sludge to improve the nutrient contents of a soil is a common practice. The soil to which a great amount of fertilizers is usually applied, may favour the solubilization of inorganic compounds. In order to study the mobility of some of these elements through the soil, we designed an experiment aimed to reproduce the behaviour of different compounds and heavy metals in the soil as a part of the non-saturated zone. A controlled experiment in a greenhouse using soil columns was used. A mineral residue from a limestone quarry in Alicante (south-east of Spain) was amended with 30 and 90 t of sludge ha⁻¹. Nitrate, ammonium, cadmium, and nickel were analysed in leachates collected at the bottom of the columns. We found high concentrations of nitrates and ammonium in leachates, which imply an important environmental risk. No important displacements of Cd and Ni were found.