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Anaerobic processing has become recognized as a simple and energy-efficient means of treating and stabilizing many high strength organic industrial wastes and is also not subjected to the operating limitations of aerobic processes. The literature review presented in this thesis outlines the advances made in the understanding of the microbiology and biochemistry of the process and the considerable advances in reactor configurations in achieving high SRTIHRT ratios. The efficacy of the anaerobic process is dependent on maintaining a high biomass concentration in the reactor, which in tum is dependent on the performance of the solids separator. The anaerobic contact process employs gravity settling for solid-liquid separation but the poor settleability of the anaerobic sludge may result in a poor performance of the contact process. By employing a much more efficient separation process such as ultrafiltration (UF), the performance of the anaerobic system can be significantly improved. In this study, therefore, a new method of operating a completely mixed anaerobic digester using a crossflow UF membrane technique was investigated in order to control the concentration of active biomass in the reactor and to determine the extent of any other advantages that can be gained over other reactor configurations. The study was carried out in four stages. In the first stage the performance of an anaerobic contact digester using a crossflow UF membrane technique was investigated for brewery wastewater treatment. The results obtained from this stage showed that under steady-state conditions, at an influent substrate concentration of approximately 120 g COD/l (100 g BOD/I) with a hydraulic retention time of 4.2 days giving an organic loading rate of 28.5 kg COO/m3.d , overall COO and BOD removal efficiencies of 99% and almost 100% respectively were achieved and the system had not reached its maximum loading capacity. Throughout the operation, HRT was maintained in the range of 2.5-4.2 days, largely determined by the flux rate. Microbiological analyses including Microscopic Count, Plate Count, Most Probable Number and Specific Methanogenic Activity test confirmed that there was almost no biomass loss through the membrane which, in tum, resulted in the maintenance of a high stability of the system under load changes. The UF membrane showed a remarkable consistency throughout the study. retaining a high concentration of active biomass in the digester and demonstrating that fouling by anaerobic biomass will reach a limiting level. In the second stage of the study the effect of Mixed Liquor Suspended Solids (MLSS) on the kinetics of the membrane reactor was investigated. The results showed that the kinetic coefficients estimated from the four steady-state runs had slight variations from each other but which could be mainly due to the changes in the numbers and the dominant species throughout the operation of the system. The increase in the MLSS concentrations did not significantly affect the kinetics of the system, In the third stage of the study the Specific Methanogenic Activity (SMA) technique was used to determine the methane production capacity of the membrane reactor, thus allowing suitable OLRs to be applied and to assess the effects of MLSS concentration on the activity of acetoclastic methanogenic bacteria in the digester. The results showed that any deterioration in acetoclastic methanogenic capacity of the system can be improved by increasing the sludge wastage rate. Ratios of the actual methane production rate to the potential methane production rate of less than 0.7 were found to be satisfactory in order to run the system efficiently in terms of COD removal and methane yield. In the final stage of the study the possible effects that membrane systems may have on the microbial population in the reactor was investigated. Therefore, microscopic examinations have frequently been carried out in order to determine the effects of the new configuration on any variation in the morphology or on the properties of methanogens as well as any change in the number of non-methanogens throughout the operation of the membrane reactor. This investigation showed that the membrane system configuration did have an apparent effect on the dominant methanogenic species throughout operation of the membrane reactor. For example Methanococcus species were the most dominant group at the beginning of the start-up period, becoming the third most dominant group at the end of the study. As a result, studying the changes in the number of viable methanogens and the dominant species may help to determine a reason for the deterioration in performance of a digester.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xvii, 264 p.; also includes graphics, maps (some col.) Includes bibliographical references (p. 236-244). Available online via OhioLINK's ETD Center

Thesis (M. Sc.)--University of Hong Kong, 2000. / Includes bibliographical references.

There is a growing demand for sustainable forms of waste management due to both legislative pressures (e.g. the European Union Landfill Directive (99/31/EC)) and increasing public awareness of environmental issues. Composting of biodegradable waste materials to produce a stabilized beneficial multi-functional product (compost) is being widely promoted. Currently, the most popular method of composting is the open windrow method, whereby the mixed and shredded feedstocks are arranged in long rows termed windrows and turned on a regular basis. During the process the waste material is subject to aerobic exothermic microbial decomposition. Commercial composting operations suffer from the problem that much of the processing is performed using empirical approaches. Improved understanding of the composting process based on scientific methodology is required to allow composting to develop its potential as an economic, safe and reliable method of sustainable waste management. This study used a series of large scale windrow-based seasonal field trials employing urban green waste as a feedstock, to investigate in unprecedented detail the temperature trends and patterns of behaviour within such structures. In addition physical-chemical profiling was undertaken. It demonstrated that windrow temperature development is not uniform in either a spatial or temporal sense. Temperature variation is a key feature of composting. All regions of typical windrows exhibited thermophilic and mesophilic temperature zones throughout the composting process. There was little seasonal variation. Sustained high temperatures were most widespread in the core regions at a height of around lm. Thus, these areas should not be favoured during temperature assessment to avoid bias results. It was demonstrated that current methods of temperature assessment are inadequate. It is suggested that greater numbers of data points are collected at varying positions and instead of simply calculating overall mean temperature that individual trends are plotted. The use of temperature frequency distribution histograms and cumulative temperature plots is additionally advised. Increased windspeed (greater than approximately 15MPH) was demonstrated to be a major factor preventing the development and sustaining of thermophilic temperatures within windrows. It is recommended that commercial composters routinely assess windspeed and direction. Changes in organic matter content, bulk density and pH provided an indication of the composting process in the long term but lacked the sensitivity of temperature measurement. Surveying using electronic tacheometry allowed changes in windrow shape and volume to be assessed. The field trial data allowed a novel physical compost model to be developed, based upon open windrow composting of urban green waste. Existing models are based on in-vessel composting systems and are technically flawed in certain key aspects. The model successfully simulated the initial stages of windrow composting, which was proven by experimentation and comparison with field trial data. The use of low level internal feedstock heating was demonstrated to be a viable method of stimulating natural enhanced microbial activity. A non- insulated model windrow and the employment of an environmental simulation system allowed the natural relationship between windrow and external environment to be modelled. The importance of such a model to the compost scientist and waste manager is highlighted. The study showed that it is possible to successfully physically model the open windrow composting process.

This thesis considers recycling as one option to improve the environmental performance of industry in the UK. A systems approach is used to identify objectives and capabilities of legislative and industrial agencies and to analyse issues in the broad context of waste policy formulation and implementation which spans both constituencies. It is shown that regulatory change to empower industrialists as decision takers is limited by a shortage of recycling infrastructure in the UK. Although well resourced firms are developing progressive waste policies in house, other firms are less well equipped to respond to regulatory pressures in a manner that is congruent with legislative objectives. An innovative option to develop recycling facilities for construction wastes at a landfill site is assessed, considering the roles of construction firms, skip hauliers and waste managers. An investigation is conducted into the practices employed by construction firms that influence wastes arising and likely changes to such practices. It is shown that pressures on construction firms are leading to some improvements to waste streaming that favour the recycling option. A spatial model of landfill catchment is used to estimate the elasticity of the volume of a given waste type delivered to a landfill site with respect to prices charged at the site and competing facilities. The option to recycle a substantial fraction of construction waste is compared with the null option of continuing to landfill waste without pre-treatment using a comparative cost benefit model. This model shows that, in the case of construction waste, benefits due to extending the working life of a landfill pit can be more significant than revenue effects for waste managers. Whether these benefits justify the costs of recycling is shown to be dependent on characteristics of particular landfill sites and

Includes bibliographical references / The trade in and management of electronic waste in Nigeria is significant because of the volumes of e-waste generated from second-hand electrical and electronic equipment (EEE) imports. Current and future e-waste discourse advocate the need for, not only an effective legislative approach, but also a sustainable approach towards e-waste management, best encapsulated through a concept known as the 'Extended Producer Responsibility (EPR)' approach. The EPR approach, which is based on the Polluter Pays Principle (PPP) places legal, financial, informative and physical(including environmental) responsibility on producers of EEE, from 'cradle-to-cradle.'The thesis groups this classification into a general term - the 'EPR Matrix,' which is utilised throughout the thesis to analyse the realistic implementation and enforcement of these responsibilities on a producer in a developing country context. Although the shipment of e-wastes between developed and developing countries is regulated under the Basel Convention 1989 and the Bamako Convention 1991, both treaties, however, do not prohibit it. The efforts of Conference of Parties (CoP) to both Conventions reveal a cognizant change in perception which is aligned with the ideals of the EPR approach to e-waste management. The realistic implementation of this approach in a developing country context is investigated, because the importer, rather than the producer is the key actor in the EEE chain. The identification of this circumstance requires that the EPR approach be extended to include the importer and other actors in the EEE chain, sharing applicable responsibilities proposed by the EPR Matrix. The thesis explores the legitimacy of this premise, by evaluating the relative success of mandatory and voluntary EPR schemes on e-waste in South Africa. Although empirical investigation reflected in the thesis reveals that voluntary industry approaches on e-waste are effective and complementary to the regulatory model, this thesis also identifies a three-tier voluntary model for effective e-waste management in South Africa, and the scope of its application. Current e-waste legislation in Nigeria reflects the adoption of the EPR approach, but in essence, the provisions are ineffective, with the absence of requisite institutions to implement its provisions. This thesis suggest that Nigerian e-waste legislation be reconsidered, with a formalization of informal e-waste markets to reflect a more resolute approach towards illegal e-waste imports and management. The certainty of a successful, and effective EPR approach in Nigeria requires a synergy of both voluntary and mandatory approaches to e-waste in that jurisdiction, and an extension of the EPR concept to include other stakeholders in industry - producers, importers, retailers, consumers and government. This thesis thus recommends the adoption of both voluntary and mandatory approaches to e-waste management in Nigeria, including an institutionalized approach, which requires the establishment of collection centres for e-waste recycling, the establishment of an EEE registry/database and proper regulation of the informal sector.