溶解氧浓度对膜生物反应器污泥特性的影响

研究了DO对膜生物反应器(MBR)中污泥特性的影响。实验结果表明:随DO的增加COD去除率和TN去除率降低,在平均进水COD为848 mg/L的条件下,DO分别为2,4,6 mg/L的MBR的COD去除率为99.12%,97.83%,97.81%;DO增加导致微生物分泌出更多的溶解性微生物产物,污泥比耗氧速率降低;DO越高,相应气水比越大,导致污泥粒径变小,污泥比阻增加。     

间歇曝气下膜生物反应器的脱氮效果与污泥特性研究

膜生物反应器(MBR)是一种新兴的污水高效处理工艺,其脱氮效能优化和污泥特性也是相关研究热点之一。研究采用间歇曝气的运行方式提高一体式MBR的脱氮效率,并考察了不同工况下活性污泥浓度及脱氮酶活性,结果表明,间歇曝气有效地强化了MBR的反硝化作用,显著地增强了其脱氮效能,而NH_4~+-N及COD的去除几乎未受影响;活性污泥浓度增长缓慢平稳,脱氢酶活性因污泥龄的延长有小幅下降,间歇曝气未显著影响污泥特性。     

共代谢膜生物反应器法处理二甲基亚砜废水

采用蔗糖作为共代谢基质与一体式好氧膜生物反应器（MBR）工艺相结合处理二甲基亚砜（DMSO）废水。考察了装置的污泥驯化效果、DMSO去除率、污泥的性能、HRT和冲击负荷对DMSO去除率的影响。试验结果表明：驯化第29天,DMSO去除率达98.5%,表明MBR内的污泥已驯化成功;在MBR运行的正式期,当DMSO处于高负荷状态时,DMSO去除率较低;随蔗糖加入量的增加,DMSO去除率逐渐提高,最终恢复到DMSO高负荷冲击前的DMSO去除效果;正常运行时,装置进水ρ（DMSO）=257~1 448 mg/L（平均值为718 mg/L）、出水ρ（DMSO）=6~22 mg/L（平均值为7 mg/L）,DMSO去除率为96.4%~99.6%（平均值为98.9%）;在MBR运行的正式期,污泥体积指数小于100 mL/g,表明污泥的沉降性能较好,MLVSS/MLSS较高,表明污泥的活性高,MBR内MLSS的平均值为5.52 g/L,MLVSS的平均值为4.78 g/L;MBR适宜的HRT为12 h。     

国外动态

改进污泥处理过程减少污泥量JWPCF,57[2],116(1985).污水处理厂污泥的处理一般采用重力增稠和厌氧消化,以稳定污泥和除臭.消化后的污泥就地堆放后倾入海中.在纽约,为了减少污泥体积,研究了多种技术,包括消化污泥的循环、倾析、淘洗-再增稠和     

污泥减量化技术研究进展

针对当前日益突出的污泥处理处置难等问题,分别从物理法、化学法和生物法等方面阐述了当前污泥减量化技术的研究发展现状,介绍了各种工艺的基本原理、特点和存在的问题.结合国内外污泥减量化技术的研究进展,提出了未来污泥减量化技术的发展方向.     

石化废水剩余污泥厌氧消化预处理技术

石化废水剩余污泥在厌氧消化时,污泥停留时间长,且产气量较低,并且反应器容积较大,所需资金投入较高.污泥厌氧消化预处理能够改变污泥特性,缩短了后续消化时间,提高甲烷产量,减少剩余污泥量.综述了各种污泥预处理技术的最新进展,分析了石化污泥厌氧消化预处理的可行性.     

污泥热水解技术研究进展

热水解可以改善污泥的生物降解性能和脱水性能,提高后续厌氧消化系统中有机物的去除率。本文阐述了热水解对污泥物理特性主要包括流变特性和脱水行为的影响;分析了热水解对污泥中氨氮浓度及对厌氧消化的作用;同时介绍了热水解技术对整个污泥处理系统能量需求的影响。指出：热水解改善了污泥的厌氧消化性能,提高了沼气等再生资源的产量,且厌氧消化产生的沼气量与热水解技术所需的能量基本平衡。     

国外动态

美国研究了自加热嗜热好氧消化和厌氧消化相结合的二段消化法。其工艺流程为:污泥和氧气分别由好气段消化器的上部、下部进入,在50—55℃下停留1小时之后进入厌氧反应器,在47—50℃下停留8天,产生的气体(含 CH_160—65%)从厌氧反应器上部排出,污泥从槽底排出。     

火电厂采用膜法实现城市中水回用的工程实践

介绍了膜法及其在城市污(中)水回用方面的技术发展、原理、工艺,并结合工程实践对火电厂采用的膜生物工艺(MBR)进行了技术经济分析和比较.     

超声波处理剩余活性污泥促进厌氧消化

用超声波处理剩余活性污泥(简称污泥),考察了污泥絮体结构、污泥中溶解性化学需氧量(SCOD)的变化规律及超声波处理对污泥厌氧消化的影响。实验结果表明,声强大于1 040W/m2时,用超声波处理污泥30m in以上,污泥絮体被打碎,污泥絮体结构遭到严重破坏,污泥中SCOD迅速增加,加速了污泥中有机质的水解反应;声强为2 000W/m2时,用超声波处理污泥60m in,中温((37±1)℃)厌氧消化10d,COD去除率为41%;厌氧消化25d的总产气量比未经超声波处理的污泥总产气量提高了53%;将发酵罐容积放大10倍,经超声波处理的污泥25d累积的总产气量比未经超声波处理的污泥总产气量提高了约25%。     

Temporal Trends in Mercury Accumulation in Lake Sediments in Sweden

Lake sediment cores were analyzedto study the history of mercury (Hg) pollution andparticularly to determine whether recent sedimentconcentrations have declined in response todeclining atmospheric deposition of Hg. Sedimentcores from 6 forest lakes distributed fromsouthern to northern Sweden and 3 northernmountain lakes were analyzed for Hg using CVAAS. A400 cm sediment profile from Måkevatten insouthwest Sweden indicates that the onset of Hgpollution occurred in the 18th century. Anindisputable increase in Hg concentrationsoccurred concurrent with the appearance ofspheroidal carbonaceous flyash particles (SCP)derived from fossil-fuel combustion, in themid-19th century. There is a strong correlationbetween Hg and SCP concentrations in the sedimentcores (r=0.67 to 0.91), which suggests a strongrelationship between historical Hg pollution andfossil fuel burning. In contrast to sediment corestaken in 1979, maximum Hg concentrations are nowobserved below the sediment surface and declinetowards the sediment surface. This study confirmsthat reductions in atmospheric deposition of Hgover Sweden have resulted in a decreased transferof total Hg to aquatic environments as reflectedby lake sediments, and that lake sediment profilesof Hg concentrations reflect relative trends inthe atmospheric deposition of Hg rather thanpost-depositional diagenetic processes.     

Elemental Concentration in Lichen in Western Anatolia

The deposition patterns of Mn, Fe, Cr, Sb, Zn and As wereinterpreted together with enrichment factor calculations. Samples collected around iron-steel plant had very high concentrations and EF values of Mn, Fe, Cr, Sb and Zn implying that these plants are serious pollution sources in the region. High As concentrations around the settlementareas showed that coal combustion is another important anthropogenic source in the region.     

Volumetric changes in landfill gas flux in response to variations in atmospheric pressure

This paper develops a quantitative model which attempts to relate volumetric changes in landfill gas emissions to variations in the surface atmospheric pressure. The model considers gas emissions as the sum of two terms, one constant over a period of weeks, and the other able to vary on a scale of hours. Results from computer simulations are given which indicate that the magnitude of the variable factor is proportional to the rate at which surface pressure is changing, rather than the actual value of the surface pressure.     

Sulphate and Nitrate in Precipitation and Soil Water in Pine Forests in Latvia

The SO₄–S and NO₃–N concentrations and pH in bulk precipitation, throughfall, stemflow and soil water for the 1994–2004 period were studied in pine forests in Latvia (Rucava and Taurene Integrated Monitoring stations). The SO₄–S and NO₃–N concentrations decreased over the study period, simultaneously with a decrease of acidity in precipitation. The changes were more evident in the western part of Latvia, probably due to declining long-range air pollution from West Europe. The trend of decreasing sulphate concentrations and increasing pH in precipitation were not followed by respective changes in soil water. In the upper soil horizon sulphate ion concentrations and acidity increased in soil water. Over the observation period, nitrate concentrations also showed an increasing trend in soil water at Rucava and Taurene, but these changes were not statistically significant.     

Variations in the Fluoride Level in Precipitation in a Region of Human Impact

The research concerns the Wielkopolski National Park (West Poland), which suffered a huge human impact in the 1970s and 1980s owing to the nearby location of an industrial plant. Since then, fundamental technological changes that it introduced into its production of phosphate fertilizers have radically reduced the amount of pollution emitted. A three-year study (2002–2004) of fluorides in precipitation in open terrain and under tree crowns showed their concentrations to range from levels below the detection limit (0.003 mg/l) to 0.560 mg/l. Those registered under tree crowns were several times higher and indicated substantial dry deposition of fluorides on the trees. The highest values were recorded in 2003, with 43% of samples ranging from 0.01 to 0.05 mg/l, and with 51% of throughfall ranging from 0.10 to 0.50 mg/l. A strong connection was shown to exist between fluoride and sulphate concentrations in the precipitation. An analysis was made of the available data on F concentrations in the air and the dust levels around the factory, but these figures did not show an unequivocal effect on F concentrations in precipitation. A great similarity was found to occur between the fluoride content in rainwater in the Wielkopolski National Park and in the centre of the nearby Poznań metropolitan area, which indicates that there are also other F sources besides the local factory.     

Difficulties in applying extended producer responsibility policies in developing countries: case studies in e-waste recycling in China and Thailand

Developing Asian countries have started to apply the principle of extended producer responsibility (EPR) to electronics and electrical equipment waste (e-waste). This policy approach aims to give electronic appliance manufacturers and importers responsibility for the collection and recycling of discarded electronic equipment. China and Thailand have drafted regulations on the recycling of e-waste with common characteristics such as the financial responsibility of producers and subsidies for collection. Although the proposed system is sensible, taking into account the fact that e-waste is a market-traded commodity, there are two major difficulties in implementing EPR in developing countries. First, it may be difficult for governments to collect funds from producers or importers if smuggled, imitation, or small shop-assembled products have a large share in the market. Second, the system creates incentives for collectors and recyclers to over-report the amount of collected e-waste in order to gain extra subsidies from the fund. Other policy measures such as the enforcement of pollution control regulations on informal recyclers, the prevention of smuggling, and the protection of intellectual property rights should accompany EPR policies.     

Medical wastes characterisation in healthcare institutions in Mauritius

This study was initiated to characterize solid and liquid wastes generated in healthcare institutions and to provide a framework for the safe management of these wastes. The project was carried at three major medical institutions, namely, the Jeetoo Hospital, the Sir Seewoosagur Ramgoolam National (SSRN) Hospital and the Clinic Mauricienne. A waste audit carried out at these sites revealed that approximately 10% of solid wastes was hazardous in nature, consisting mainly of infectious, pathological and chemical wastes. The average amount of hazardous wastes per patient per day was found to be 0.072 kg at Jeetoo hospital, 0.091 kg at SSRN hospital and 0.179 kg at the clinic. The amount of hazardous wastes generated as a function of the number of occupied beds was found to follow a relationship of type y=0.0006x-0.19, where y was the amount of hazardous wastes generated per bed per day and x was the number of occupied beds. The waste quantifying process also revealed that at SSRN Hospital, 0.654 m(3) of water was being consumed per patient per day and the amount of wastewater produced was 500 m(3)/day. Further analysis revealed that the wastewater was polluting with chemical oxygen demand (COD), biological oxygen demand (BOD(5)), total suspended solids (TSS) and coliform content well above permissible limits.     

Future trends in computer waste generation in India

The objective of this paper is to estimate the future projection of computer waste in India and to subsequently analyze their flow at the end of their useful phase. For this purpose, the study utilizes the logistic model-based approach proposed by Yang and Williams to forecast future trends in computer waste. The model estimates future projection of computer penetration rate utilizing their first lifespan distribution and historical sales data. A bounding analysis on the future carrying capacity was simulated using the three parameter logistic curve. The observed obsolete generation quantities from the extrapolated penetration rates are then used to model the disposal phase. The results of the bounding analysis indicate that in the year 2020, around 41–152 million units of computers will become obsolete. The obsolete computer generation quantities are then used to estimate the End-of-Life outflows by utilizing a time-series multiple lifespan model. Even a conservative estimate of the future recycling capacity of PCs will reach upwards of 30 million units during 2025. Apparently, more than 150 million units could be potentially recycled in the upper bound case. However, considering significant future investment in the e-waste recycling sector from all stakeholders in India, we propose a logistic growth in the recycling rate and estimate the requirement of recycling capacity between 60 and 400 million units for the lower and upper bound case during 2025. Finally, we compare the future obsolete PC generation amount of the US and India.     

Medical waste generation in selected clinical facilities in Taiwan

This study investigated the type and amount of medical waste generated from small clinical facilities in Taiwan. We sampled 200 small medical establishments, with few or no patient beds, to survey the wastes generated and disposed. The surveyed medical facilities consisted of four groups including private clinics, medical laboratories, blood centers and public clinics. Private clinics providing surgical, dental, obstetrical, and dialysis services were included in this survey because they may generate higher amounts of infectious waste than other specialties. The overall mean general waste production rate was 3.97 kg/bed/day (or 0.075 kg/patient/day) at all the surveyed facilities, higher than that obtained from larger hospitals in Taiwan, which ranged from 2.41 to 3.26 kg/bed/day. The highest amount of infectious wastes generated among the four groups of facilities were from blood centers (3.14 kg/bed/day), followed by private clinics, medical laboratories and public clinics (1.91, 1.07, and 0.053 kg/bed/day, respectively). The overall average was 2.08 kg/bed/day. This study suggests that the waste generated at small medical facilities ranged widely.     

A systematic approach to in situ bioremediation in groundwater

In situ bioremediation (ISB) melds an understanding of microbiology, chemistry, hydrogeology, and engineering into a strategy for planned and controlled microbial degradation of specific contaminants. ISB creates subsurface environmental conditions, typically through reduction oxidation manipulation, which induce the degradation of contaminants via microbial catalyzed biochemical reactions. In turn, the microbes produce enzymes that are utilized to derive energy and that are instrumental in the degradation of target chemicals. To accomplish this chain of events, the type of microorganisms, contaminant, and the geological conditions at the site must be considered. Since in situ conditions are manipulated by engineered means, the most important consideration is the ability to transmit and mix liquids in the subsurface. The Interstate Technology Regulatory Council (ITRC)–ISB Team has recently completed a guidance document that describes a systematic approach to ISB in groundwater. ITRC is a state‐led coalition of more than 40 states working together with industry and stakeholders to achieve regulatory acceptance of environmental technologies. © 2003 Wiley Periodicals, Inc.