The advantages associated with the use of sewage sludge in agricultural land have motivated many countries to use sewage sludge for soil amendment purposes. South Africa’s deteriorated agricultural soil could benefit from this nutritional and cost effective product. However, the major shortcoming of sewage sludge is the presence of various pathogenic microorganisms. This raised concern amongst researchers with regard to public safety. The focus of this study, was to investigate the prevalence of pathogens in a crop grown in soil enriched with sewage sludge and to determine risk of infection thereof and to suggest appropriate management practice for sewage sludge use. Potato (Solanum tuberrosum), which is a high risk crop was used, to simulate a worst case scenario. Both the low metal sludge (LMS) and high metal sludge (HMS) were found to have associated diverse numbers of bacteria. Using culture-based technique, E.coli and Salmonella spp were found to persist in soil throughout the experimental period. One treatment option (LMS 16 tons/ha) showed a prevalence of these microorganisms in potatoes. Subsequent molecular studies based on amplification of 16S rRNA gene, yielded limited contamination of potatoes with enteric pathogens, however diverse types of opportunistic, pathogens (mostly environmental pathogens) were isolated from the potatoes. Enteric pathogens were isolated from the sewage treated soil in which these potatoes were grown. This study has indicated that growing even high risk crops, may lead to limited infestation of produce with primary pathogens. However, proper treatment of sewage sludge prior to use in agriculture is recommended to ensure public safety. The management requirements indicated in this study serve as recommended actions that can be implemented to ensure human safety with regard to sludge application to agricultural land. / Thesis (PhD (Water Utilisation))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

The first part of this diploma thesis targets in the formation of summary of methods of sewage sludge thermal treatment. Sludge is dangerous material rising from water treatment. Original water pollution is concentrated in sludge. Spectrum of the different methods of sludge disposal is very vast, thermal methods belong to the most advanced ones. Nowadays, legislative rules and regulations make more restrictive, hence sludge disposal is problematic because of economic and ecological view of point. The second part of this diploma thesis is dealt with perspective sludge management at the Central Waste Water Treatment Plant Prague concerning sludge drying and consequent sludge incineration.

Digitized by Kansas Correctional Industries

No description available.

The specific research work described in this thesis forms part of a much larger research project that was funded by the Technology Programme of the UK Government. This larger project considered improving the design and efficiency of membrane bioreactor (MBR) plant by using modelling, simulation and laboratory methods. This research work uses phenomenological mechanistic models based on MBR filtration and biochemical processes to measure the effectiveness of alternative behavioural models based upon input-output system identification methods. Both model types are calibrated and validated using similar plant layouts and data sets derived for this purpose. Results prove that although both approaches have their advantages, they also have specific disadvantages as well. In conclusion, the MBR plant designer and/or operator who wishes to use good quality, calibrated models to gain a better understanding of their process, should carefully consider which model type is selected based upon on what their initial modelling objectives are (e.g. using either a physically mechanistic model or an input-output behaviourial model). Each situation usually proves unique. In this regard, this research work creates a "Model Conceptualisation Procedure" for a typical MBR which can be used by future researchers as a theoretical framework which underpins any newly created model type. There has been insufficient work completed to date on using a times series input-output approach in the model development of a wastewater treatment plant, so only general conclusions can be made from this research work. However, it can be stated that this novel approach seems to be applicable for a membrane filtration model if care it taken to select appropriate input-output model structures, such as those suggested in the "Model Conceptualisation Procedure". In the case of the development of a MBR biological model, it is thought that a conventional Activated Sludge model produced by the IWA could be coupled to a input-output model structure as suggested by this report to give a hybrid model structure that may have the advantages of both model types. Further research work is needed in this area. Future work that should follow on from this research study should focus on whether these input-output models could be used for predictive control purposes, whether an integrated model could be created, and whether a benchmark could be created for the three main MBR configurations.

The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,1993-1995 / published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

This thesis investigated the final products from the current effluent treatment system for woolscouring (wool washing) plants, namely, (i) sludge produced from the chemical flocculation of solids in the wastewater from the wash bowls, and (ii) concentrated suint (sheep sweat) produced from evaporation of the liquid phase separated from the sludge. In addition, fibrous wastes from the woolscouring process were studied. The aims of the study were to (i) investigate whether suint could be applied in a sustainable way to arable land as a potassium fertiliser, and (ii) assess the conditions under which the sludge could be composted for use as a soil conditioner to return organic matter to soil. Experiments involving suint were performed at both laboratory and glasshouse scales, while experiments involving the solid woolscour wastes were based both in the laboratory and using a small-scale (4.5 m3 total capacity) in-vessel composting unit established at a New Zealand woolscour. Decomposition was measured using net-nitrogen mineralisation and weight loss methods. Suint, the water-soluble contaminants on the fleece, contained high levels of potassium (20% on a dry weight basis) and also appreciable quantities of sulphur, sodium, and chlorine. Biological treatment before evaporation stabilised the resulting suint and improved the consistency of its composition. Suint did not affect the soil processes examined, in that it partly decomposed in soil, did not inhibit the turnover of model organic compounds, did not affect soil properties such as pH and electrical conductivity, and did not lead to increased leaching of mineral nitrogen. Suint was either neutral or positive towards plant performance when applied to soil at a rate of 100 kg potassium per hectare. Suint was therefore judged to be suitable for application to land and could be targeted to soils known to be deficient in potassium or to areas where crops with a high potassium demand are grown. Sludge, composed of dirt (soil particles, faecal matter, and skin and fibre debris) and wool grease, was highly variable in terms of its rate of decomposition, ranging from 0.8 to 27.8% of the initial total nitrogen mineralised over 30 days at 37℃. Fibrous wastes, such as opener (fibre and contaminants removed from the wool by agitation prior to scouring) and scoured wool cleaner (wool fibre and dust removed from scoured and dried wool) wastes, also showed variability in decomposition rates. Sludge decomposition was improved by as much as threefold when co-incubated with fibrous wastes. Although it was shown that the polyacrylamide and pesticide content of sludge did not inhibit its decomposition, the effect of the grease content was not fully understood. Chemical properties of woolscour sludge, such as the carbon to nitrogen ratio, suggested that sludge was a substrate of good resource quality. From a biological perspective, however, the data suggested that woolscour sludge was limited in available nutrients; sludge nitrogen was derived principally from keratin, which decomposed at a low rate resulting in the slow release of mineral nitrogen and low levels of microbial activity. Thus, sludge appeared a poor substrate for composting. However, the results from composting trials indicated that the sludge could be successfully processed after blending with a bulking agent such as sawdust. The blended material showed a 90% reduction in wool grease over 21 days of composting when the moisture content of the composting mass was kept optimal. Compost temperature exceeded 55℃ when wool fibre was added to the blend. Initial results from a case study involving the commercial composting of the entire sludge production (16 tonnes per day) from a New Zealand woolscour indicated that a saleable compost could be produced from a material that would otherwise go to landfill, and served to illustrate the commercial significance of these research results.

Endocrine disrupting compounds (EDCs) together with potentially toxic metals (PTMs), are present in large amounts in sewage sludge which was used as a tool to expose terrestrial molluscs to environmental concentrations of these pollutants. Pastures fertilised with sewage sludge had significantly fewer adult slugs collected per replicate (C: 58.4; T: 26.2; S.E.D. 0.14; p&lt;.05) and eggs (C: 16.6; T: 9.1; S.E.D. 0.17; p&lt;0.05).  No differences with treatment, in tissue concentrations of EDCs or PTMs or in hepatopancreas or gonad structure, were detected.  However, hepatopancreatic proteins (cyclophilin, paramyosin and trypsin) were significantly altered (p&lt;0.01). In a laboratory study, exposure, via feed, to 0x (Control), 1x (T1), 10x (T2) or 110x (T3) the environmental dose of sludge extract resulted in a dose-related increase in mean mortality rates (relative to controls) in adult slugs (<i>Deroceras reticulatum</i>).  Exposure for 3 weeks induced no measurable differences in tissue pollutant concentrations or hepatopancreas or gonad histology. Fewer slug eggs exposed to sludge and/or dehydration (2x2; 10 eggs/replicate); hatched following sludge exposure (C hydrated 64.5%;T hydrated 24.5%; p&lt;0.05; S.E.D. 2.169; C dehydrated 48.9%; T dehydrated 17.4%; p&lt;0.05; S.E.D. 4.256) but not following dehydration.  There was no significant interaction between sludge exposure and dehydration but survival was lowest in animals exposed to both. Slug behaviour was affected by exposure to sludge, including increasing avoidance and huddling behaviours. The results indicate that terrestrial molluscs may be used as invertebrate sentinels to assess the effects of ECD and PTM exposure.