DISTRIBUTED DISCHARGE OF COOLING WATER ALONG DIRECTION OF STREAM FLOW1

ABSTRACT. A multiple-outfall system for cooling water disposal which is distributed along the direction of stream flow is analyzed. The results provide a simple method of preliminary design of a cooling water discharge outfall system and for a quick extimate of water quality of a polluted stream. It is shown that a properly designed distributed discharge system is capable of preventing serious pollution due to localized discharge of wastes and waste heat; however, the final design of the discharge system should take into account alternative schemes of waste heat disposal and their economic consequences.     

POTENTIALS FOR REUSE OF WASTEWATER IN NORTH CENTRAL TEXAS1

ABSTRACT There are several possible ways in which wastewater from municipalities may be reclaimed and reused so as to minimize the need for imported water in North Central Texas. The rationale for reuse is enhanced by the fact that new water quality requirements in the Trinity River system will necessitate a very high degree of treatment at municipal sewage plants, just for discharge to surface streams. The largest potential market for municipal effluent is the steam-electric power industry. Within the next decade the generating capacity for electric power in North Central Texas will have to be more than doubled to meet increasing demand. Adequate supplies of condenser cooling water for such expansion will be difficult to obtain and assure. New large power stations might advantageously be located adjacent to municipal wastewater treatment plants, to utilize effluent as make-up water for cooling towers. Experience elsewhere has shown that well-treated wastewater can be used for cooling tower make-up with a minimum of trouble, with a considerable saving in overall cost, and with conservation of pristine water for other uses.     

THERMAL DISCHARGES AND PUBLIC POLICY DEVELOPMENT1

ABSTRACT The generation of electric energy in steam-electric power plants is accompanied by the discharge of large quantities of waste heat into the environment. In most cases, this heat is released into natural bodies of water at temperatures relatively close to ambient. In certain locations, such as the Chesapeake Bay, discharges of waste heat may triple in the next decade. It is expected that past practices of thermal discharge, if continued into the future, will result in significant damages to other legitimate users of the water resource, both present and future. This paper reviews the economic causes of these potential damages, and describes the role of public policy as one of removing such causes through regulation incentive or intervention. Possible public policies are reviewed, including prohibition, standards, various types of dollar incentives such as taxes and subsidies, marketable effluent permits, and direct government investment. The innovative power plant siting program recently adopted in Maryland is also discussed. It is concluded that no statements can be made regarding the comparative efficiency or effectiveness of the various policies at the present state of knowledge. It is recommended that policy-makers adopt mixed strategies, preserving as many options as possible for dealing with similar problems in the future.     

The maturity tests during the composting of municipal solid wastes

This study investigated at first the evolution of co-composting process of municipal solid waste and sewage sludge under Tunisian pedo-climatic conditions.Results showed that the temperature profiles established in the system revealed three classical steps, the mesophilic phase during the first 25 days, the thermophilic phase between 30 and 130 days and the cooling phase began after the 14th week in the two windrows W1 (100% of municipal solid wastes) and W2 (60% of municipal solid wastes and 40% of dried sewage sludge). Potential toxic heavy metal content appeared generally more important in W2 than W1, and both finished products of compost obtained in this study satisfied most parts of the recommended norms of agronomical use. The presence or absence of nitrifying activity allowed determining that the compost W1 was more mature than the compost W2.Composting cannot only transform waste by reducing its harmful effect but also corrects when added to soil, the deficit in organic matter. The nature of the raw material used in composting may affect the quality of the final product. There is a significant need for the amendment of soils by compost. The quality of the amendment may have a significant impact on environment.     

上海市污泥集装化运输可行性研究

随着上海市生活垃圾集装化运输系统的逐步完善和发展,上海市污泥的集装化运输逐渐被提上日程。本文通过对上海市中心城区的10座城市污水处理厂的污泥产量、污泥含水率、污泥运输道路和装卸环境等进行系统调研,综合分析和研究了上海市各污水处理厂污泥集装化运输的可行性,并进一步研究了污泥性质对集装化运输的影响。结果表明,上海市中心城区仅白龙港污水处理厂含水率约为60%的深度脱水污泥符合污泥集装化运输的要求;深度脱水污泥性质较为稳定,对各种钢材料的腐蚀性为0.00016~0.00125 mm/a,对集装化运输影响较小,但污泥释放的氨气浓度高达173.66 mg/m3,影响集装化运输,需采取水雾喷洒等措施进行控制。     

市政污泥与高浓度废弃物的厌氧共消化：一种生物质能源净产生的途径

厌氧共消化是一种绿色、实用的回收废弃物中能源的技术。本文介绍了厌氧共消化技术的原理，并介绍了美国佐治亚州F. Wayne Hil水资源处理中心采用油脂废弃物（FOG）和含糖工业废水与市政污泥进行连续流厌氧共消化的实际应用案例。结果表明，厌氧共消化可显著提高甲烷产量达2倍以上，甲烷产量随着高浓度有机废弃物负荷率及厌氧消化反应器停留时间的延长而增加，且COD和VS降解率可保持在合理范围内，经济效益显著。     

Composting and compost application in China

The current situation of municipal solid waste (MSW) and sewage sludge production (in terms of volume as well as composition) in China is introduced. Composting and compost application in China are reviewed. In China, the production of municipal solid waste and sewage sludge is changing rapidly along with economic development. Composting is mainly applied for treating MSW, about 20% of the total amount of MSW being disposed. MSW composting is mainly co-composted with night soil or sewage sludge. Compost is used in agriculture, forestry and horticulture. Compost application is the key factor influencing the composting development in China. To promote composting and compost application in China, a state-wide survey on the production, composition and physical and chemical properties of MSW and sewage sludge should be carried out. More effort should be made to develop low cost and high efficient composting technologies according to China's conditions. The environmental impact of compost application should also be given more attention.     

Environmental assessment of supercritical water oxidation of sewage sludge

Environmental aspects of using supercritical water oxidation (SCWO) to treat sewage sludge were studied using a life cycle assessment (LCA) methodology. The system studied is the first commercial scale SCWO plant for sewage sludge in the world, treating sludge from the municipal wastewater treatment facility in Harlingen, TX, USA. The environmental impacts were evaluated using three specific environmental attributes: global warming potential (GWP), photo-oxidant creation potential (POCP) and resource depletion; as well as two single point indicators: EPS2000 and EcoIndicator99. The LCA results show that for the described process, gas-fired preheating of the sludge is the major contributor to environmental impacts, and emissions from generating electricity for pumping and for oxygen production are also important. Overall, SCWO processing of undigested sewage sludge is an environmentally attractive technology, particularly when heat is recovered from the process. Energy-conserving measures and recovery of excess oxygen from the SCWO process should be considered for improving the sustainability potential.     

Phosphorus sorption and availability in soils amended with animal manures and sewage sludge

Soils that receive large applications of animal wastes and sewage sludge are vulnerable to releasing environmentally significant concentrations of dissolved P available to subsurface flow owing to the gradual saturation of the soil's P sorption capacity. This study evaluated P sorption (calculated from Langmuir isotherms) and availability of P (as CaCl2-P and resin P) in soils incubated for 20 d with poultry litter, poultry manure, cattle slurry, municipal sewage sludge, or KH2PO4, added on a P-equivalent basis (100 mg P kg(-1)). All the P sources had a marked negative effect on P sorption and a positive effect on P availability in all soils. In the cattle slurry- and KH2PO4-treated soils, the decreases in P sorption maximum (19-66%) and binding energy (25-89%) were consistently larger than the corresponding decreases (7-41% and 11-30%) in poultry litter-, poultry manure-, and sewage sludge-treated soils. The effects of cattle slurry and KH2PO4 on P availability were, in most cases, larger than those of the other P sources. In the poultry litter, poultry manure, and sewage sludge treatments, the increase in soil solution P was inversely related (R2 = 0.75) to the input of Ca from these relatively high Ca (13.5-42 g kg(-1)) sources. Correlation analyses implied that the magnitude of the changes in P sorption and availability was not related to the water-extractable P content of the P sources. Future research on the sustainable application of organic wastes to agricultural soils needs to consider the non-P- as well as P-containing components of the waste.     

城市垃圾和污水脱水污泥、排水管污泥混合堆肥工艺研究

城市垃圾和污水脱水污染、排水管污泥已成为现代城市污染的主要总是。由于这些废弃物中有机物质的含量较高,因此可以利用堆肥的方法来进行处理,使其转化为农田的有机肥料,本文用城市生活垃圾和污水处理厂污泥、排水管污泥混合进行堆肥的研究。     

氧化铝行业水污染控制措施探讨

根据氧化铝行业生产用水及排污特点,结合某氧化铝生产企业生产废水的处理实践,推荐采用逆向洗涤赤泥和氢氧化铝,节约用水量;综合利用赤泥洗液和含碱废水;对生产用水设置循环水系统和二次利用水系统;设置生产废水处理站,氧化铝系统和热电厂的生产系统排水、循环水系统的排污水,以及化验等废水全部排入生产废水处理站处理,废水经处理后作为二次利用供水返回生产系统使用,通过综合利用生产废水,可以实现厂区废水的零排放,节约资源的同时,提高清洁生产水平,避免对环境造成污染。     

Industrial waste to energy by circulating fluidized bed combustion

Industrial waste is a good resource from the viewpoint of efficient waste management. The vital need for energy utilization and environmental protection mean it is of interest to develop circulating fluidized bed combustion (CFBC) to burn solid wastes with low pollutant emissions. The paper presents some explanatory studies on waste-to-energy in a pilot scale CFCB facility. A series of combustion/incineration tests have been carried out for the industrial wastes: petroleum coke, waste tire and sludge cakes with various moisture contents. It seems that the CFBC has feed flexibility without modifying heat transfer equipments for energy recovery. In addition, the results of experimental tests demonstrate that gas emissions from waste incineration in CFBC can be well controlled under local regulation limits.At normal operation temperature in CFBC (approx. 800°C), the heat transfer coefficient between bulk bed and bed wall is on the order of 10² W/m^2° C, which is useful to estimate the energy recovery of waste combustion by CFBC. A practical and simple guide is proposed to estimate the energy recovery from waste combustion by CFBC, and to find maximum allowable moisture content of waste if there is to be any energy recovery without auxiliary fuel.     

ECOLOGICAL MANAGEMENT PROBLEMS CAUSED BY HEATED WASTE WATER DISCHARGE INTO THE AQUATIC ENVIRONMENT1

Discharge of heated waste water may affect the entire aquatic ecosystem–the interrelated biological, chemical, physical system–and, if the temperature change is large, may destroy the capacity of the ecosystem to serve a variety of beneficial purposes. However, it is possible to discharge heated waste water in carefully controlled amounts without seriously degrading the aquatic ecosystem. There are four basic alternatives which are open to us with regard to the heated waste water problem which we may choose singly or in various combinations: (1) Placing all heated, waste water in streams, lakes, and oceans without regard to the effects. Thus considering the environmental damage as a necessary consequence of our increased power demand. (2) Using, but not abusing, existing ecosystems. This means regulating the heated waste water discharge to fit the receiving capacity of the ecosystem. (3) Finding alternative ways to dissipate or beneficially use waste heat. (4) Modifying ecosystems to fit the new temperature conditions. We are all dependent upon a life-support system which is partly industrial and partly ecological. Unfortunately, we have reached a stage of development where the non-expandable, ecological portion of our life-support system is endangered by the expanding industrial portion. Optimal function and full beneficial use of both portions of our life-support system will only be possible if a variety of disciplines and diverse points of view can cooperate and work together effectively. Since wastes in amounts that are acceptable taken one at a time may be lethal collectively, environmental management should be on a regional basis.     

Immersion frying for the thermal drying of sewage sludge: an economic assessment

This paper presents an economic study of a novel thermal fry-drying technology which transforms sewage sludge and recycled cooking oil (RCO) into a solid fuel. The process is shown to have significant potential advantage in terms of capital costs (by factors of several times) and comparable operating costs. Three potential variants of the process have been simulated and costed in terms of both capital and operating requirements for a commercial scale of operation. The differences are in the energy recovery systems, which include a simple condensation of the evaporated water and two different heat pump configurations. Simple condensation provides the simplest process, but the energy efficiency gain of an open heat pump offset this, making it economically somewhat more attractive. In terms of operating costs, current sludge dryers are dominated by maintenance and energy requirements, while for fry-drying these are comparatively small. Fry-drying running costs are dominated by provision of makeup waste oil. Cost reduction could focus on cheaper waste oil, e.g. from grease trap waste.     

城市污泥干燥焚烧一体化处理工艺的研究

城市污泥的产量日益增加,若不进行处理,不仅浪费土地资源而且污染环境。对污泥中的水分形式和污泥的处理工艺进行了分析,认为污泥的干燥和焚烧是最完全、稳定的处理工艺。提出一种城市污泥干燥焚烧一体化处理工艺,利用污泥自身焚烧产生的热值,提供干燥系统所需的热量,达到整个污泥处理系统能量的基本自给。对该系统的流程和各工艺进行了分析,结果表明该系统的污泥减量大、干燥效率高、运行成本低、尾气排放有效控制。     

Refrigeration waste heat utilization for drying applications: a review

ABSTRACT

Cold chain industry has a vast potential for waste heat recovery. It is a matter of importance for energy efficiency point of view, as global energy demand is increasing day by day. Ample amount of low-grade energy is either unutilized or underutilized. The heat rejected by a Heat pump or refrigeration system emerged as a promising solution for dehydration by utilizing low-grade waste heat despite higher investment. As compared to solar drying technology, heat pump drying evolved as a reliable method regarding better process control, energy efficiency, and quality of the product to be dried. Energy utilized through the refrigeration system’s waste/exhaust heat recovery in combination with or without renewable energy source enhances the overall efficiency of the system and also reduces the cost. This useful review investigated and compared the research findings of waste heat utilization through heat pump and from condenser of refrigeration system on laboratory, pilot as well as industrial scale for drying of various fruits, vegetables, and agro products. Various drying parameters like drying rate, moisture content, Specific Moisture Extraction Rate (SMER), Coefficient of Performance (COP), Exergy efficiency, and temperature as well as humidity conditions inside the drying chamber were also reviewed to promote the technological advancement of energy utilization by commercial cold storage waste heat recovery.     

Frequency Control Characteristics of a Direct-Mode Untreated Sewage Source Heat Pump in the Heating Mode

An untreated sewage source heat pump system directly makes use of the urban raw sewage instead of that treated by a sewage plant. At present In China, most systems adopt the indirect mode for avoiding the harmful effect of the sewage on the heat pump unit. In this article a direct-mode untreated sewage source heat pump system, which shows less theoretical analysis of the mathematical model, is theoretically designed and analyzed to simulate the system dynamic characteristics in the heating mode. The results show that the system COP changes from 4.1 to 3.4 and the heating capacity from 9.5 to 15.3 kW when the sewage inlet temperature is 12°C and the frequency increases from 18 to 32 HZ. The condenser heat-transfer coefficient increases with the frequency reducing while the change trend of evaporator heat-transfer coefficient is the opposite. The highest values of them are 303 and 1617 W.m^?2?K^?1, respectively. The frequency control simulation supplies the operation adjustment with theoretical instructions and some reference values.     

Health-care waste management in India.

Health-care waste management in India is receiving greater attention due to recent regulations (the Biomedical Wastes (Management & Handling) Rules, 1998). The prevailing situation is analysed covering various issues like quantities and proportion of different constituents of wastes, handling, treatment and disposal methods in various health-care units (HCUs). The waste generation rate ranges between 0.5 and 2.0 kg bed-1 day-1. It is estimated that annually about 0.33 million tonnes of waste are generated in India. The solid waste from the hospitals consists of bandages, linen and other infectious waste (30-35%), plastics (7-10%), disposable syringes (0.3-0.5%), glass (3-5%) and other general wastes including food (40-45%). In general, the wastes are collected in a mixed form, transported and disposed of along with municipal solid wastes. At many places, authorities are failing to install appropriate systems for a variety of reasons, such as non-availability of appropriate technologies, inadequate financial resources and absence of professional training on waste management. Hazards associated with health-care waste management and shortcomings in the existing system are identified. The rules for management and handling of biomedical wastes are summarised, giving the categories of different wastes, suggested storage containers including colour-coding and treatment options. Existing and proposed systems of health-care waste management are described. A waste-management plan for health-care establishments is also proposed, which includes institutional arrangements, appropriate technologies, operational plans, financial management and the drawing up of appropriate staff training programmes.     

Reclamation of wastes contaminated by copper,lead, and zinc

Waste materials containing toxic levels of copper, lead, and zinc, such as mine and smelter wastes, present difficult conditions for the establishment of vegetation. This article reviews the many attempts which have been made to reclaim these wastes. Inert wastes from mining and quarrying operations, such as slate quarry waste and certain colliery shales, seem to be good materials for reclaiming wastes contaminated by copper, lead, and zinc. Organic wastes, such as sewage sludge and domestic refuse, may provide only a temporary visual improvement and stabilization of the toxic materials.Nontolerant plant materials may often be planted directly on modern waste materials, which are less toxic than they were in the past. However, tolerant plant materials are needed for revegetating waste materials produced by early and more primitive extraction methods.     

WATER AND WATER PROBLEMS IN THE SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT AND SOME POSSIBLE SOLUTIONS1

ABSTRACT: It is estimated that by about 1984 water demand in the District will nearly equal Nature's average annual replenishment of the supply and that, thereafter, unless means are developed to augment our in-District resources, water mining will be required on a grand scale. Sources of augmentation include: (1) reduction of wastes; (2) industrial recycling of previously-used water; (3) use of municipal sewage effluents; (4) desalination of brackish ground water; (5) aquifer recharge from all available, high-quality sources, particularly flood waters; and (6) importation of excess waters from such out-of-District sources as the lower courses of the Suwannee and Apalachicola Rivers. To achieve maximum beneficial uses of in-District sources a regional water and sewer authority is needed that can develop and transmit water from all available sources to the various county and city systems on a wholesale basis. It is envisioned that such a supply system would tie together all production sources, much as the electrical generation and supply systems are currently organized into regional electric power hookups. At least two bills are currently before the Florida Legislature to achieve these goals.