H.David Stensel – författare
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2 produkter
2 produkter
Optimisation of Corrosion Control for Lead in Drinking Water Using Computational Modelling Techniques
Häftad, Engelska, 2013
1 822 kr
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In many respects, lead in drinking water has become a forgotten problem, since the mid 1980s when a range of environmental controls were implemented to reduce exposure to lead. This is largely because the sampling protocols, that underpin regulatory controls, are mostly inadequate and have tended to under-estimate the amount of lead that can be present in drinking water (IWA, 2010). Optimisation of Corrosion Control for Lead in Drinking Water Using Computational Modelling Techniques shows how compliance modelling has been used to very good effect in the optimisation of plumbosolvency control in the United Kingdom, particularly in the optimisation of orthophosphate dosing. Over 100 water supply systems have been modelled, involving 30% of the UK’s water companies. This “proof-of-concept” project has the overall objective of demonstrating that these modelling techniques could also be applicable to the circumstances of Canada and the United States, via three case studies. This report is the first in the Research Report Series published by the IWA Specialist Group on Metals and Related Substances in Drinking Water. Authors: Dr. C. R. Hayes and Dr. T. N. Croft Collaborators A. Campbell, City of Ottawa Water (CA) I. P. Douglas, City of Ottawa Water (CA) P. Gadoury, Providence Water (US) M. R. Schock, US Environmental Protection Agency (US)
Evaluation of Feasibility of Methods to Minimize Biomass Production from Biotreatment
Häftad, Engelska, 2004
1 822 kr
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This report presents the results of an evaluation of technologies that may result in less biomass production in activated sludge processes. The report summarizes the results of a comprehensive literature review that was done to evaluate technologies in terms of their sludge reduction potential, ease of implementation, impacts on plant operations and effluent quality, reliability, and relative capital and operating costs. Reporting testing results supported significant biomass reduction by processes using chemical and thermal methods, higher life forms (predator processes), anaerobic instead of aerobic respiration, and extreme solids retention times, but biomass reduction for enhanced biological phosphorus removal (EBPR) processes and a mechanical disintegration process were less conclusive. The predator enhancement process showed promise for industrial wastewater treatment, but is less attractive for municipal wastewater treatment for which a lower soluble COD fraction is present. Extreme solids retention time processes may be practical for small wastewater flows and perhaps with the use of membrane separation technology. Anaerobic treatment processes are known to have a lower biomass yield (one fourth or a less than for aerobic treatment), but work is needed to develop their applications for low strength, low temperature wastewaters, such as in municipal wastewater treatment. For some processes such as the cell disruption using mechanical, thermal, and chemical means, the cost of implementing the biomass reduction technology was greater than the cost savings associated with less sludge production. Addition of chemical uncouplers can greatly reduce biomass production, but pose problems of toxic chemicals in the treated effluent. In a series of bench-scale tests carried out at the Seattle West Point wastewater treatment facility and the University of Washington environmental engineering laboratories the presence and mechanism of COD loss (and subsequent less biomass production) in the anaerobic zone of EBPR processes was investigated. The results of the test work and fundamental evaluation could not support previous claims of a COD loss in EBPR processes, nor was less sludge production observed.