户用沼气工程发展对农田养分流动的影响

该文采用养分流的分析方法,对比分析2007年中国13个沼气发展省份沼气农户和非沼气农户农田养分管理行为的差异。结果显示：两类农户单位面积化肥用量和秸秆还田率方面没有明显差异,部分地区沼气农户生活燃料比例明显减少,但地头秸秆燃烧情况加剧;粪尿养分还田率有较大不同,非沼气农户粪尿直接还田率达到96%,沼气农户只有39%,沼气农户大量粪尿进入沼气池,但只有33%的养分被利用,沼肥养分仅占沼气农户养分输入总量的9%。综合比较,沼气农户家庭有机养分比重仅有24%,而非沼气农户达到了43%;这导致了沼气农户单位面积养分输入总量为 781.62 kg/hm2,显著低于非沼气农户的850.82 kg/hm2。沼气农户的废弃物养分循环利用率只有45%,而非沼气农户达到70%。研究结果表明中国沼气农户并没有因为沼气发展而提高养分再利用,沼肥对化肥的替代效果没有表现出来,导致有机资源浪费。因此,必须加强沼气农户的技术培训,加强沼肥的还田力度,提高养分循环利用率,充分发挥沼气对家庭养分资源再利用的优势。     

乌当区垃圾资源化处理的思考

针对垃圾围城的趋势越来越严重,从垃圾回收的意义出发,指出了垃圾分类回收的意义,对可回收利用的垃圾进行分类,引出垃圾分类回收利用的方法,同时结合乌当区目前正在运行的污水处理厂产生的污泥,提出了探讨性的解决措施,以缓解用地紧张问题。     

浙江省竹林生态与竹材循环利用实践

竹林是浙江省主要森林资源,按照生态经济学原理,对竹林进行生态经营,能够更好地发挥竹林的生态效益和经济效益。文章论述了浙江省竹林生态经营的意义和现状,提出了竹林生态经营的优先研究领域。以竹资源开发为基础的竹产业经济是浙江经济迅速发展的重要引擎,而基于资源培育、产品开发和废弃物综合利用的竹业循环经济发展模式是提高资源利用效率的有效途径。     

含铬皮革废水污灌和施用含铬污泥时铬在土壤环境中的残留

采样分析了污灌区铬的土壤环境背景值,计算了铬的土壤环境容量以及用含铬皮革废水污灌和施用含铬污泥后铬在土壤中的积累和残留量。     

Microbiological and chemical changes in two arable soils after long-term sludge amendments

 Sludge amendments increase the input of carbon and nutrients to the soil. However, the soil concentrations of heavy metals and xenobiotica can also increase due to sludge amendments, with possible effects on soil microorganisms and soil fertility. Therefore, we studied the effects on soil microorganisms and soil chemistry in two arable soils after 12 and 16 years of sewage sludge amendment (0, 1 and 3 dry matter ha^–1 year^–1). The sludge amendments were combined with nitrogen addition at three rates according to crop requirements, and all combinations were replicated 4 times, giving a total number of 36 parcels at each experimental site in a non-randomised block design. Univariate data evaluation as well as principal component analysis and discriminant function analysis (DFA) were used to identify differences between treatments in microbial and chemical parameters. The DFA showed that acid and alkaline phosphatase, potential ammonium oxidation and total nitrogen were the most important parameters to discriminate between a priori defined groups of sludge treatments. Among the heavy metals, copper showed the highest increase in soil concentration with sludge amendments, but this increase was still not high enough to have a significant influence on the measured parameters. None of the xenobiotica investigated was found in high soil concentrations. In conclusion, the present study showed that the sewage sludge affected several of the biological and chemical parameters investigated. However, no severe negative effects on soil microorganisms were detected at these moderate levels of sludge amendment. Received: 3 December 1998     

Quality of brackish aquaculture sludge and its suitability for anaerobic digestion and methane production in an upflow anaerobic sludge blanket (UASB) reactor

Intensive recirculating aquaculture systems (RAS) produce high volumes of biosolid waste. The high salinity of brackish/marine sludge limits its use in landfill sites and waste outflows and it is a source of pollution. A reduction in sludge mass would therefore minimize the potential environmental hazard and economic burden stemming from its disposal. The aims of the current study were: 1) to characterize brackish aquaculture sludge (BAS) from three RAS in order to test for potentially suitable treatments, and 2) to test the BAS's suitability for anaerobic digestion in an upflow anaerobic sludge blanket reactor (UASB). Brackish sludge from three intensive RAS was collected periodically and analyzed for a variety of physical and chemical parameters. The mean sludge electrical conductivity and pH values ranged from 4.0 to 8.6 mS cm^− 1 and 7.0 to 7.7, respectively. A low sludge redox potential averaging − 80 mV and dissolved oxygen concentrations of less than 1 mg l^− 1 indicated the existence of anaerobic conditions. Volatile solids comprised 56 to 76% of the dry weight and the sludge volume index ranged from 44 to 69 ml g ^− 1. High concentrations of total nitrogen and total carbon were also observed, resulting in a C:N ratio ranging between 8.1 and 10.3. Toxic and/or inhibitory compounds for methanogenesis such as nitrites, nitrates and sulfides were almost absent. Sludge BOD₅ ranged from 10 to 30% dry weight. These data suggest that BAS may be used in anaerobic digestion and methanogenesis without pretreatment. This concept was tested by digesting aquaculture sludge in UASB reactors. Despite the high sulfate and phosphate concentrations in the BAS, these were found not to be inhibitory to methanogenesis. Up to 70% sludge-mass reduction and an average of 40% methane production were demonstrated.     

Trace metals in two garden products derived from sewage sludge

Abstract

Yields were decreased in soybean (Glycine max L. C.V. Hawkeye), mint (Mentha viridis L. ), and barley (Hordeum vulgare L. C.V. Atlas 57) when grown in 50% Yolo loam soil and 50% of either of two commercial garden sewage sludge products. The trace elements Zn, Cu, Mn, and B were elevated in plants grown with the high‐level amendments. No Cd and little Ni were detected in shoots.     

稻田复种轮作系统能流物流特征研究

稻田复种轮作是循环农业发展的重要措施, 能量转化与物质循环是生态系统的基本功能之一, 是农田生态系统最主要的研究内容之一。为探明稻田复种轮作这一耕作制度的优势, 采用田间定位试验的方法, 对稻田生态系统连作处理方式和轮作处理方式的能流与物流特征进行比较分析。研究结果表明: 稻田复种轮作系统能提高农田生态系统的能量流动与物质循环。在能量流动方面, 稻田轮作处理平均总初级生产力为74.37×10¹⁰ J.hm^-2, 比连作处理高31.35%; 轮作系统能量总投入平均为9.42×10¹⁰ J.hm^-2, 比连作处理高4.90%; 轮作系统的光能利用率平均为1.55%, 比连作处理高31.36%; 轮作处理辅助能量产投比平均为7.89, 比连作处理高25.04%。在物质循环方面, 轮作处理的N、P、K养分利用率明显高于连作处理, 各个处理的N、P输出/输入均小于1, 说明农田生态系统中N素、P素均有盈余, 呈正平衡状态, 有利于土壤N素、P素的良性循环; 但是系统中K素的输入值小于系统内K素的输出, 说明系统内存在严重的K素亏损。因此, 在南方稻区, 采用稻田复种轮作方式有利于提高系统的能流物流, 从而使农田生态系统处于良性循环, 对循环农业发展有良好的促进作用。     

污泥热解产物与可回收热值分布规律研究

[目的]研究污泥热解产物及其可回收热值的分布规律。[方法]采用固定床试验系统,研究了热解温度对污泥热解产物特性的影响,着重分析了热解温度对气体产物组成、热值以及热解液热值的影响,以及污泥热解产物质量分布与热量分布随温度的变化规律。[结果]热解温度越高,气体产物的产率越高,且抑制了热解液的生成。在450~850℃下恒温热解时,650~850℃下CH4产量稳定。随着热解温度升高,CO和H2析出量显著增加,单位质量污泥产生气体热值增加。随着温度升高,热解液热值先增加后降低,在550~650℃下热解时达最大值。气液产物总热值在650~850℃下热解时最高,850℃下热解时气体热值所占比例达69.5%。[结论]该研究为污泥高效热解能源化技术的实现提供了理论依据。     

Nutrient discharge,sludge quantity and characteristics in biofloc shrimp culture using two methods of carbohydrate fertilization

The aim of this study was to evaluate the effect of two methodologies of carbohydrate fertilization on the volume and characteristics of effluent from intensive biofloc shrimp cultivation. Six fiberglass circular tanks (50 m² each) were divided into two treatments. In the treatment called continuous (CONT), the tanks received daily molasses fertilization throughout the entire rearing period. In the treatment named initial (INI), molasses was used only in the early weeks of cultivation. Juvenile Litopenaeus vannamei (0.87 ± 0.10 g) were stocked at a density of 180 animals m⁻² and cultured during 12 weeks until they reached an average weight of 12 g. The tanks were operated with no water exchange and the total suspended solids concentration were kept between 300 and 400 mg L⁻¹ using settling chambers. The sludge produced and the wastewater at harvest were quantified and their characteristics were determined. The production of TSS in the CONT treatment was higher (0.25 kg of solids per kg of applied feed) than in the INI treatment (0.16 kg kg⁻¹) (P < 0.05). The analysis of the sludge revealed a high amount of volatile solids in both treatments, between 636 and 702 g kg⁻¹. However, due to the elevated sludge nitrogen content, the carbon to nitrogen (C:N) ratio was low, with values of 6.4 ± 1.4 and 7.5 ± 1.6 for INI and CONT respectively. The BOD:TSS ratio was also low in both treatments, but the INI showed lower values (10.3 ± 0.6%) than the CONT (14.9 ± 0.0%) (P < 0.05). Both fertilization strategies were able to modify the characteristics of sludge produced during cultivation. Moreover, the high nitrogen and sulfate content of the sludge in both treatments indicated that it may be difficult to use an anaerobic digestion process to treat sludge. In the INI treatment tanks, the sludge is partially stabilized, while in the CONT there was a greater need for stabilization.