污泥堆肥土地利用对土壤环境及高羊茅特性的影响

结合北京市污泥堆肥土地利用现状．研究了污泥堆肥对土壤环境及高羊茅（Festuca arundinace。）的影响。旨在为北京市污泥堆肥用于高羊茅园林生产提供理论依据,促进资源再利用。研究结果表明．施用污泥堆肥增加了高羊茅栽植小区土壤养分含量,特别是土壤中有机质含量增加明显,与空白对照相比增加了43．9％～73．2％,对土壤养分状况具有一定的改良效果;施用污泥堆肥后,高羊茅栽植小区土壤中重金属含量虽有不同程度的增加。但均远低于相关标准限值．且土壤重金属污染综合指数小于土壤安全限值0．7．表明种植小区土壤未受到重金属污染：施用污泥堆肥对高羊茅生长具有一定的促进作用．与空白对照相比．高羊茅总生物量增长率为16．7％～50．0％。综合分析试验结果,确定污泥堆肥用于高羊茅的适宜施用量为2kg／m^2。     

Impact of sewage sludge applications on the biogeochemistry of soils

This report describes an investigation into the bioavailability and fate of trace metals and their subsequent impact on important soil microbiological functions such as nitrification, denitrification and methane oxidation in low and high Cu containing soils in the presence and absence of residual organic matter from sewage sludge additions made 10 years earlier. The soils being studied are part of long term sewage sludge trials and include a low Cu soil (13.3 mg Cu/kg soil, 4.18 LOI %), left un-amended to serve as a control soil, soil amended with a high Cu sewage sludge (278.3 mg Cu/kg soil, 6.52 LOI %) and soil amended with a low Cu sewage sludge (46.3 mg Cu/kg soil, 6.18 LOI %). Soil was also amended with inorganic metal salts (273.4 mg Cu/kg soil, 4.52 LOI %) to further investigate the impact of Cu in the absence of additional organic matter contained in applied sewage sludge. Data from the first two years of a project are presented which has included field-based studies at long term sewage sludge trials based in Watlington, Oxford, UK and laboratory based studies at the Institute of Grassland & Environmental Research, North Wyke, Devon, UK.     

Energy and nutrient recovery from sewage sludge via pyrolysis.

Energy recovery and nutrient reuse from sewage sludge has traditionally been achieved via anaerobic digestion/power generation with land application of the biosolids. By contrast, thermal processes such as pyrolysis have typically been used only for energy recovery. One such technology has demonstrated at commercial scale that all of the energy in sludge can be beneficially recovered and reused. No attempt was however made to recover and reuse sludge nutrients. There are many potential benefits of using pyrolysis for both energy and nutrient recovery. Firstly, unlike digestion, the principal energy product is oil, which can readily be stored and used when required, ensuring that energy recovery is maximised. Secondly is that the sludge nutrients are recovered in the pyrolysis char. Laboratory soil incubation studies using char from the Subiaco demonstration plant were conducted over an eight-week period to confirm nutrient availability. Results from this study showed that the phosphorus in the char is plant available although the nitrogen was insoluble. Based on these results it appears that there is potential to use pyrolysis as an effective means to recover and reuse both the energy and the very valuable phosphorus present in sewage sludges.     

Beneficial reuse of precast concrete industry sludge to produce alkaline stabilized biosolids.

The precast concrete industry generates waste called concrete sludge during routine mixer tank washing. It is highly alkaline and hazardous, and typically disposed of by landfilling. This study examined the stabilization of municipal sewage sludge using concrete sludge as an alkaline agent. Sewage sludge was amended with 10 to 40% of concrete sludge by wet weight, and 10 and 20% of lime by dry weight of the sludge mix. Mixes containing 30 and 40% of concrete sludge with 20% lime fulfilled the primary requirements of Category 1 and 2 (Canada) biosolids of maintaining a pH of 12 for at least 72 hours. The heavy metals were below Category 1 regulatory limits. The 40% concrete sludge mix was incubated at 52 degrees C for 12 of the 72 hours to achieve the Category 1 and 2 regulations of less than 1000 fecal coliform/g solids. The nutrient content of the biosolids was 8.2, 10 and 0.6 g/kg of nitrogen, phosphorus and potassium respectively. It can be used as a top soil or augmented with potassium for use as fertilizer. The study demonstrates that concrete sludge waste can be beneficially reused to produce biosolids, providing a long-term sustainable waste management solution for the concrete industry.     

Toxicity assessment of the extract of compost as a final product from Bio-Toilet.

Bio-Toilet is the name of a dry closet or composting toilet using sawdust as an artificial soil matrix for bioconversion of human excrement into compost. Since feces and urine contain several chemicals such as pharmaceutical residues and endocrine disruptors and they may still remain in compost after biological reaction in the Bio-Toilet, it is required to examine the possibility of soil and/or groundwater pollution by applying compost to a soil system in farmland. In this study, toxicity of Bio-Toilet compost was evaluated by measuring the viability of human neuroblast (NB-1). The bio-assay was applied to the water extract of compost from the Bio-Toilets which are in practical use in Japan. The assay results showed that (1) the extract of feces showed no toxicity, and the extracts of unused sawdust had no or low level toxicity and (2) the extracts of composts had heavier toxicity than unused sawdust. These results implied that some chemicals that have toxicity were generated by biological reactions or accumulated in toilet system. The bioassay results with fractionated organic matter by its molecular weight showed that the small molecular weight fraction had stronger toxicity than other fractions. The effect of inorganic matter on toxicity was examined by comparing the dose-response relationship of the extracts of compost with positive control with 1M of sodium chloride solution. The comparison showed that sodium concentration in the extract was too low to develop the toxicity and the effect of inorganic matter could be neglected in this study.     

Kraft mill sludge to improve vegetal production in Chilean Andisol.

The effect of kraft mill sludge addition (25 to 75 ton/ha) to soil derived from volcanic ashes (Andisol) on wheat (Triticum aestivum L.cv. Puken) biomass production, and in the nutrient absorption by the plants was evaluated. Respiration activity and seed germination tests were carried out on the soil/sludge mixtures, in order to evaluate possible toxic effects due to the sludge addition to the soil. Soil without sludge was used as a control treatment. The plants were grown in a greenhouse (25 degrees C, 14 h-photoperiod) during 120 days, then the plants were collected and dried at 65 degrees C for 72 h for the determination of biomass production (root and aerial) and analyzed for mineral content (Ca, Mg, K and P). The mixtures of soil/sludge showed no toxicity. Seed germination and respiration activity increased with the increment of the sludge. The accumulated CO2 in the soil without sludge was 41.66 mg CO2/100; this value shows a low microbial activity. The biomass increased with the increment of sludge addition to the soil and five times more biomass was obtained when 75 ton/ha sludge was added to the soil. The nutrient absorption efficiency was also improved with the sludge addition.     

Reuse of treated wastewater and sewage sludge for fertilization and irrigation

The objective of the present work was to assess the short-term potential of treated wastewater and sewage sludge for ornamental lawn fertilization and irrigation. A field experiment was performed and the following treatments were considered: sewage sludge application + irrigation with public water; sewage sludge application + irrigation with treated wastewater; irrigation with public water; irrigation with treated wastewater (TW). Irrigation with treated wastewater showed a positive effect on lawn installation through higher growth of grass (1,667 cm) and higher dry matter yield (18,147 g m(-2)). These results represent a significant increase in the grass yield compared with public water irrigation. The grass height (2,606 cm) and dry matter yield (23,177 g m(-2)) increased even more, when sewage sludge produced in the wastewater treatment plant (WWTP) was applied to soil, which proves once more its benefits as an organic fertilizer. At the end of the experiment, an increase of some soil parameters (pH, electrical conductivity, organic matter, Ca2+, Na+, K+, Mg2+ and NH4+) was observed, indicating that treated wastewater irrigation can cause a soil sodization. This short-term study indicated that use of treated wastewater and sewage sludge for ornamental lawn fertilization and irrigation is an environmentally sustainable option for re-use of the WWTP by-products.     

城市污泥基本特性与安全处置

通过分析污泥的基本特性,如含水率,燃烧值,污泥的肥分及污泥中的重金属含量和营养物质的含量,来进一步研究分析污泥的处置方法。着重介绍了卫生填埋、污泥焚烧、水体消纳等处置方法,以及污泥在农业、建材方面的安全应用,为污泥的安全处置及资源化利用提供了依据。     

Phytotreatment of sludges (Phragmites australis) for their reuse in the environment

The aim of this study is the evaluation of the agronomic characteristics acquired by a phytotreated sludge coming from a wastewater treatment plant (WWTP) located in Tuscany (central Italy). The chemical characterization showed values which are within the Italian legislation limits for mixed composts. From an agronomic point of view, the sludge did not present a level of phytotoxicity, as shown by the germination index (GI% = 77). Furthermore, pathogen compounds are inexistent (Escherichia coli < 1,000 CFU/g). Different substrates (obtained by mixing the sludge with sandy agronomic soil - 0.5% w/w, 1% w/w, 2.5% w/w and 5% w/w) were prepared in order to evaluate the best mixture performance in terms of water retention capacity and plant growth. No significant differences were observed for all sludge mixtures. Different plants were tested in plots (Lepidium sativum, Cucumis sativus and Avena sativa). The best plant adaptation, measured as dry biomass production, was observed for Avena sativa. The results obtained underlined that the phytotreatment of sludge can bring about the transformation of sewage sludges into organic products that are reusable in agriculture, if previously mixed with other appropriate materials and taking into account their heavy metal content.     

A tool to evaluate the fertiliser value and the environmental impact of substrates from wastewater treatment.

Fertilisers may contain pollutants that are applied to the field together with the nutrients. Comparing fertilisers is difficult because of their different concentrations of nutrients and pollutants. In this study an already existing model was taken. It was further developed to compare nutrient fluxes (N, P, K, Ca, Mg, S, humus) and pollutants (heavy metals and pharmaceuticals) of pig and cattle slurry as well as human urine. The data used is taken from literature and, in the case of pharmaceuticals in urine, daily excretion rates were calculated. An amount of 19 m3 ha(-1) a(-1) undiluted urine can be applied, limiting factor is sulphur. Without taking over-fertilisation into account, an addition of mineral fertiliser is required to any organic fertiliser application. In general, heavy metal, antibiotic, and hormone fluxes are higher by using animal manure then urine as fertiliser. However, additional loads of other pharmaceuticals consumed by humans have to be considered. Overall, the model is a suitable tool worthwhile to be extended in aspects of hygiene, environmental impacts as for example, degradation processes as well as ecotoxicology.     

城市污泥中氮磷在壤土和砂土中的淋溶实验研究

研究探讨了壤土和砂土上施用城市污泥对地下水中氮和磷的影响。以北京市高碑店污水处理厂的生污泥和庞各庄堆肥厂的堆肥作为土壤施加的污泥源,采用自制土柱淋溶模型的方法研究壤土和砂土上施用不同污泥量时灌水对土柱中pH、氮、磷的淋出情况,测定分析淋滤液中的pH值、总氮和总磷。实验设计4种处理,分别为污泥施用量占土壤干重的0(不施污泥,对照处理)、2%、4%和6%。实验结果表明:淋滤液的pH值显著变低;总氮和总磷以波动方式逐渐降低,并随淋洗次数的增多逐渐低于空白对照水平,而且壤土和砂土中淋滤液的变化规律不同。污泥添加2%时淋滤液氮磷含量最低,堆肥添加4%时淋滤液氮磷含量最低。污泥施用到壤土和砂土上,适量时不会造成地下水氮磷的污染,同时有益于土壤养分的保持,减少养分流失。     

The role of sludge conditioning and dewatering in the fate of nonylphenol in sludge-amended soils.

One of the main concerns associated with the recycling of biosolids to arable land is their contamination by organic pollutants, like endocrine disruptors. Conditioning and dewatering are usually the last steps of the sewage sludge treatment, before its further utilization. The choice of the specific conditioning/dewatering method may have an effect, not only on the amount of residues in the biosolids, but also on the fate of these compounds in amended soils. Anaerobically digested wastewater sludge was conditioned at lab-scale by means of physical and chemical methods and subsequently dewatered by centrifugation. The produced biosolids plus non-conditioned and non-dewatered sludges were amended separately to soil and spiked with 14C radiolabelled single isomer of nonylphenol. The persistence and leaching potential of nonylphenol after an incubation period of three months were correlated to the sludge treatment method. In comparison to non-conditioned sludge, 54% and 72% higher amount of pollutant residues were extractable when freeze-thawed and limed sludge, respectively, were used. Conditioning of sludge with cationic polymer decreased the leaching potential of nonylphenol in sludge-amended soils, while liming increased it. Fractions of the model compound recovered as extractable and bound residues were analyzed in order to interpret nonylphenol fate.     

Potentials of using nanofiltration to recover phosphorus from sewage sludge.

Due to the depletion of mineral phosphorus resources there is an increasing demand for efficient phosphorus recovery technologies. In this study the potential of nanofiltration to recover phosphorus from pre-treated sewage sludge is investigated. The efficiency of three commercial nanofiltration membranes (Desal 5DK, NP030; MPF34) was tested using model solutions. Desal 5DK showed the best selectivity for phosphorus. A pH of lower than 1.5 was found to be most suitable. Desal 5DK was used on four different sewage sludge ash eluates and on one sewage sludge. In these experiments it was shown that a separation of phosphorus from undesired components such as heavy metals was possible with significant variations in the efficiency for the different ash and sludge types. Additionally the achievable product recovery was investigated with model solutions. A product recovery of 57.1% was attained for pH 1 and 41.4% for pH 1.5.     

What is the potential for utilizing the resources in sludge?

The successful strategy for water protection by biological wastewater treatment results in a sludge production of about 20 to 40 kg dry matter per population equivalent and year. In the context of regional material fluxes, sewage sludge has a low resource potential and a low pollution potential despite the fact that it can be characterised as a sink, concentrating wastewater compounds. The mass flow of nutrients (N, P) in the sewage sludge is comparatively small as compared to the losses of nutrients in agriculture. The most valuable element in the sludge is phosphorus, as the availability of phosphorus for the production of low-cost mineral fertiliser is limited. The most economical means of P-recycling is agricultural sludge application, which can also be seen as the option with the lowest loss of all valuable compounds of the sludge, and the lowest increase of entropy. The reliability of this disposal route for the treatment plant operator depends on several major pre-requisites: * reliability in regard to hygiene * reliability in regard to long-term soil protection public acceptance (politicians, media) * acceptance by all parties involved in sludge application and its consequences (farmers, farmer unions, land owners, food industry, food trade, retailers, consumers, consumer associations, NGOs, etc.) Only the first two prerequisites can be based on scientific research and risk assessment. As a consequence, only for these two aspects can quality criteria and adequate procedures be developed and introduced into a legal framework and quality assurance procedures. The latter two pre-requisites must be addressed in terms of sociology, psychology and political science and have a strong educational aspect.     

Agricultural use of municipal wastewater sludges: phosphorus availability of biological excess phosphorus removal sludges.

Reuse of sewage sludges as phosphorus fertiliser requires the estimation of the plant availabilities of phosphorus (P) from different sludges. This study investigates the effect of lime stabilisation on the phosphorus availability from biological phosphorus removal sludges. In the first part of the study, pot experiments were carried out to assess the fertilising effect of a dewatered biological phosphorus removal sludge. Availability of P was determined in terms of plant-uptake. In the second part of the study, incubation tests were carried out to observe the change in the available P with time when the waste activated sludge (WAS) from an enhanced biological phosphorus removal (EBPR) process is mixed with the same soil. In this part, the plant available P was measured in terms of Olsen extractable P. A P-deficient, alkaline soil was used in the experiments and Lollium Perenne was selected as the testing plant. The results of the pot experiments revealed that lime-stabilisation of the sludge considerably decreased or retarded the availability of P in the sludge. In the incubation tests, the availability of phosphorus in the lime stabilised and nonstabilised sludge amended soil samples was close to each other. In general, P-availability was increased due to the sludge application except for the lime-stabilised dewatered sludge.     

A strategy for reducing pollutants at source in order to obtain sustainable agricultural recycling of wastewater sludge

The Swedish licensing system for wastewater sludge use in agriculture, REVAQ, sets challenges. These include a maximum nominal accumulation rate of 0.2%/year on farmland, for specified metals, to be reached by 2025. Here a model is suggested, and applied for the Gothenburg regional wastewater treatment plant, Gryaab, to quantify historic sludge quality improvements and necessary future development. Local sampling campaigns covering two decades show a substantial reduction of heavy metals and ecologically harmful organic substances (such as adsorbable organic halogens, nonylphenols, phthalates, naphthalenes and polycyclic aromatic hydrocarbons) from households and society at large. For the metals studied the historic mass flow reduction to sludge varies from 1 to 2%/year for mercury, zinc and copper to 15%/year for silver. Copper needs further reduction, involving water pipes and copper roofing. Silver is rare in soil, and significant reduction from already low levels is needed to reach the accumulation goal. Further reduction of other metals involves addressing storm- and drainage water entering the sewers and the sediments already in the sewers. Fulfilling the goals of REVAQ implies national and local measures affecting public and private stakeholders including property owners, the wastewater collection system, commercial businesses and legislating authorities.     

Processing dewatered sewage sludge using electrokinetic technology.

High content of heavy metals and presence of pathogens in the dewatered sewage sludge have been the main obstacles for land application of sewage sludge-made fertilizer. The aim of this study was to examine the effects of the innovative electrokinetic (EK) technology on removal of heavy metals from sewage sludge, on the reduction of pathogens, and on sludge chemical characteristics. The results showed that the removal efficiencies for Zn, Cu, Ni, Cr, As and Pb were 94.9%, 95.4%, 89.7%, 67.8%, 31.2% and 18.7%, respectively. Acidification pretreatment of the dewatered sludge for 29 h decreased the content of heterotrophic bacteria from 1.5 x 10(8) c.f.u./g of wet sludge to 1.1 x 10(4) c.f.u./g of wet sludge. Although the initial content of total coliforms and fecal coliforms in sewage sludge were 5.8 x 10(5) c.f.u./g of wet sludge and 4.0 x 10(5) c.f.u./g of wet sludge, respectively, no viable cells were detected. Minor losses of K and N were detected, but the loss of P was found to be significant in EK treated sewage sludge. The treated sludge was technically considered as very stable based on the carbon dioxide evolution rate.     

Eucalyptus Camaldulensis Invasion in Riparian Zones Reveals Few Significant Effects on Soil Physico‐Chemical Properties

Many invasive alien plants alter soil‐nutrient regimes of invaded ecosystems, affecting management outcomes. We assessed the effects of Eucalyptus camaldulensis invasions on physical and chemical properties of riparian soils in the Western Cape Province, South Africa. Samples were collected from topsoil beneath the canopy of uninvaded and a gradient of invaded sites, namely, light, moderate and heavy over four seasons. We quantified soil moisture, temperature, litter depth and thickness, primary textural components, concentrations of soil macro (C, N, P and K) and micro (Mn, Zn, Cu and Fe) nutrients, and pH. Available N (NO₃^?‐N and NH₄⁺‐N) and P, as well as exchangeable Ca and Mg were also assessed. Soil pH levels were significantly lower in invaded than in uninvaded sites in all seasons. Soil moisture decreased consistently with invasion intensity. Concentrations of macro, micro and available nutrients did not vary significantly along the invasion gradient (p > 0.05), but exchangeable cation content was significantly higher in uninvaded than in invaded sites, especially in winter and spring. Sites invaded by E. camaldulensis had higher litter build‐up than non‐invaded sites, but this appears to have little effect on soil‐nutrient regimes. It appears that restoration following removal of invasive stands of E. camaldulensis will not require major interventions to return soil to pre‐invasion conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Heavy metal displacement in EDTA-assisted phytoremediation of biosolids soil.

Chelating agents are added to soil to solubilise the metals for enhanced phytoextraction. Yet no studies follow the displacement and leaching of heavy metals in soil with biosolids following solubilisation with chelates. The objective of this work was to determine the mobility of heavy metals in biosolids in a soil from a sludge farm that had received biosolids for 25 years. The soil was placed in columns in a greenhouse. Columns either had a plant (poplar) or no plant. After the poplar seedlings had grown for 144 d, the tetrasodium salt of the chelating agent EDTA was irrigated onto the surface of the soil at a rate of 1 g per kg of soil. Drainage water was analysed for three toxic heavy metals and four essential heavy metals. Without EDTA, concentrations of the seven heavy metals in the leachate from columns with or without plants were low or below detection limits. With or without plants, the EDTA mobilised all heavy metals and increased their concentration in drainage water. Without plants, the concentrations of Cd, Cu, Fe, and Zn in the leachate from columns with EDTA were above drinking-water standards. The presence of poplar plants in the soil reduced the concentrations of Cu, Fe, and Zn in the leachate so it fell within drinking-water standards. Concentrations of Cd and Pb in the leachate remained above drinking-water standards with or without plants.     

Strategy for nutrient control in modern effluent treatment plants.

The fate of nutrients in the modern effluent treatment plant depends on several factors, for example type of treatment plant, availability of nutrients in the specific effluent, dosing of nutrients and sludge age/production. New technologies with the aim to increase the efficiency and stability of the conventional activated sludge process have strongly affected the possibilities to control discharge of nutrients in pulp and paper effluents. A paradox is that a reduction of organic material may often lead to an increase of nutrient discharges. It is of the utmost importance that the operators have good knowledge of the factors affecting nutrient uptake and release in order to minimise nutrient discharge and obtain optimal plant performance. Dosing of nitrogen and phosphorus is one key factor in the sensitive balance in most pulp and paper effluent treatment plants. Correct dosing is crucial as high or low doses might lead not only to increased discharge of nutrients but also to severe operational problems with poor sludge quality, which in turn affects the plant performance for longer periods.