Model evaluation and optimisation of nutrient removal potential for sequencing batch reactors

Performance of sequencing batch reactors for simultaneous nitrogen and phosphorus removal is evaluated by means of model simulation, using the activated sludge model, ASM2d, involving anoxic phosphorus uptake, recently proposed by the IAWQ Task group. The evaluation includes all major process configurations with different aerobic, anoxic, anaerobic sequences, and fill conditions. Basic relationships between modelling and design based on overall process stoichiometry are established for the interpretation of nutrient profiles associated with different operation modes. A similar approach is also used for the assessment of the effect of major operating parameters on system performance. WaterSA Vol.28(4) 2002: 423-43

Composition and Distribution of Extracellular Polymeric Substances in Aerobic Flocs and Granular Sludge

Extracellular polymeric substances (EPS) were quantified in flocculent and aerobic granular sludge developed in two sequencing batch reactors with the same shear force but different settling times. Several EPS extraction methods were compared to investigate how different methods affect EPS chemical characterization, and fluorescent stains were used to visualize EPS in intact samples and 20-µm cryosections. Reactor 1 (operated with a 10-min settle) enriched predominantly flocculent sludge with a sludge volume index (SVI) of 120 ± 12 ml g–1, and reactor 2 (2-min settle time) formed compact aerobic granules with an SVI of 50 ± 2 ml g–1. EPS extraction by using a cation-exchange resin showed that proteins were more dominant than polysaccharides in all samples, and the protein content was 50% more in granular EPS than flocculent EPS. NaOH and heat extraction produced a higher protein and polysaccharide content from cell lysis. In situ EPS staining of granules showed that cells and polysaccharides were localized to the outer edge of granules, whereas the center was comprised mostly of proteins. These observations confirm the chemical extraction data and indicate that granule formation and stability are dependent on a noncellular, protein core. The comparison of EPS methods explains how significant cell lysis and contamination by dead biomass leads to different and opposing conclusions

Swirl Flow Bioreactor coupled with Cu-alginate beads: A system for the eradication of Coliform and Escherichia coli from biological effluents.

It is estimated that approximately 1.1 billion people globally drink unsafe water. We previously reported both a novel copper-alginate bead, which quickly reduces pathogen loading in waste streams and the incorporation of these beads into a novel swirl flow bioreactor (SFB), of low capital and running costs and of simple construction from commercially available plumbing pipes and fittings. The purpose of the present study was to trial this system for pathogen reduction in waste streams from an operating Dewats system in Hinjewadi, Pune, India and in both simulated and real waste streams in Seattle, Washington, USA. The trials in India, showed a complete inactivation of coliforms in the discharged effluent (Mean Log removal Value (MLRV) = 3.51), accompanied by a total inactivation of E. coli with a MLRV of 1.95. The secondary clarifier effluent also showed a 4.38 MLRV in viable coliforms during treatment. However, the system was slightly less effective in reducing E. coli viability, with a MLRV of 1.80. The trials in Seattle also demonstrated the efficacy of the system in the reduction of viable bacteria, with a LRV of 5.67 observed of viable Raoultella terrigena cells (100%)

UN water action decade: A unique challenge and chance for water engineers

In the year 2000, the UN General Assembly resolved the Millennium Development Goals (MDGs), and all the Member States of the UN pledged to take any measures to get the MDGs achieved. Concerning water supply and sanitation, a rough calculation clearly tells that it is impossible to meet the MDGs by just copying and pasting the traditional technology as it has been developed in the industrialized countries. Novel concepts and technologies have to be developed, tested and made available which allow fast implementation for a reasonable price, and which provide high treatment efficiency, reliability and robustness. Based on the latest estimates on population growth and migration rates it appears that top priority should be given to investments in the water infrastructure of municipalities. Introduction of water re-use systems should be favoured to avoid over-exploitation of local water resources. Suggested are step changes of the infrastructural system components with emphasis on technology innovation. Many small steps are often more effective than a single big one. In the attempt to quickly improve local situations specific attention should be paid to modern physico-chemical methods based on membrane technology. Decentralized wastewater treatment and re-use methods should be installed simultaneously to the construction of new houses. Further development of methods for separate collection and treatment of particularly composed waste streams should be encouraged. Wastewater should be rated as a source of valuable materials rather than a nuisance. Technology development should proceed hand-in-hand with the development of the societal, economical and political framework. Concerted actions are necessary to make novel technology function. Otherwise, meeting of the MDGs will remain an illusion. Keywords Millennium development goals; source control; sustainability; wastewater treatment; water re-use; water suppl

Sustainable water management in rural and peri-urban areas: what technology do we need to meet the UN Millennium Development Goals?

Installation of advanced urban water management systems is one of the most important first steps in the attempt to overcome poverty on earth, outbreak of diseases, crime and even terrorism. Because world wide application of traditional water supply, sewerage and wastewater treatment technology requires financial resources which are basically not available within a reasonable short time frame novel solutions must be found, developed and implemented. The combination of high-tech on-site treatment of the various waste streams generated in households, enterprises and industrial sites, and reuse of the valuable materials obtained from the treatment plants, including the purified water, is one of the options which is investigated by various groups of researchers and technology developers, nowadays. This concept may help meeting the UN Millennium Development Goals, provided people are ready to accept this new way of dealing with household wastes. Education is necessary to build up the foundation which modern water technology can be based upon. In parallel, tailored modifications are to be considered to satisfy the specific demands of local communities. In this context, female participation appears to be extremely important in the decision making process. Keywords UN Millennium Development Goals; urban water management; flushing sewer concept; source separation; female involvemen

Application of FISH and CLSM/Image Analysis for Microbial Examination in Biological Wastewater Treatment in China

Water in China' brings together a number of articles which describe the current situation in China with respect to surface water quality and wastewater treatment, and provide results of specific research projects, leading the way to a China-specific up-to-date water treatment technology

Aerobic granular sludge in an SBR-system treating wastewater rich in particulate matter

Aerobic granular sludge was successfully cultivated in a lab-scale SBR-system treating malting wastewater with a high content of particulate organic matter (0.9 gTSS/L). At an organic loading rate (CODtotal) of 3.4 kg/(m3.d) an average removal efficiency of 50% in CODtotal and 80% in CODdissolved was achieved. Fractionation of the COD by means of particle size showed that particles with a diameter less than 25-50 mm could be removed at 80% efficiency, whereas particles bigger than 50 mm were only removed at 40% efficiency. Tracer experiments revealed a dense sessile protozoa population covering the granules. The protozoa appeared to be responsible for primary particle uptake from the wastewater