Activated Sludge Foaming - New Publication

PhD student Martin Fryer and Professor Nick Gray of the Water Technology Research Group, based in the Centre for the Environment have published a new and precise method for estimating foam development in full scale aeration tanks in wastewater treatment plants. Foaming is a major problem in the operation of activated sludge treatment which is a biological process that treats 90% of wastewater in the developed world. The new methodology opens up the possibility of better foam prediction allowing more time for operators to prevent problematic foam occurring; as well as now being able to measure the effect of remedial action. The foaming Scum Index (FSI) has been presented in the latest issue of the Journal of Environmental Management.



Fryer, M. and Gray, N.F. (2012) Foaming Scum Index (FSI) – A new tool for the assessment and characterization of biological mediated activated sludge foams. Journal of Environmental Management , 110, 8-19. Doi:10.1016/j.jenvman.2012.05.009

New Paper on Co-treatment of Acid Mine Drainage with Domestic Wastewater

In a new paper published by Theresa Hughes of the Water Technology Research Group the concept of treating acid mine drainage with conventional domestic wastewater using activated sludge has been shown to be a viable option. Using a synthetic drainage toxicity tests showed that activated sludge can withstand high proportions of AMD (EC50 19–52% AMD by volume). Laboratory-based sequencing batch reactors were also used to examine the treatability of AMD. Results from OUR inhibition tests on acclimatized activated sludge indicated that over a relatively short timescale (21 days), the activated sludge microbial community can adapt to AMD sufficiently so that shock loads of metals and acidity do not significantly inhibit OUR.
Theresa A. Hughes and N. F. Gray (2012) Acute and Chronic Toxicity of Acid Mine Drainage to the Activated Sludge Process. Mine Water and Environment, 31, 40–52 (DOI 10.1007/s10230-011-0168-y) Link

New Research Paper from the Water Technology Research Group.

The latest research paper from the Water Technology Research Group

Dubber, D. and Gray, N.F. (2011) The influence of fundamental design parameters on ciliates community structure in Irish activated sludge systems. European Journal of Protistology, 47, 274-286.

Abstract
The protozoan community in eleven activated sludge wastewater treatment plants (WWTPs) in the greater Dublin area has been investigated and correlated with key physio-chemical operational and effluent quality parameters. The plants represented various designs, including conventional and biological nutrient removal (BNR) systems. The aim of the study was to identify differences in ciliate community due to key design parameters including anoxic/anaerobic stages and to identify suitable bioindicator species for performance evaluation. BNR systems supported significantly different protozoan communities compared to conventional systems. Total protozoan abundance was reduced in plants with incorporated anoxic and anaerobic stages, whereas species diversity was either unaffected or increased. Plagiocampa rouxi and Holophrya discolor were tolerant to anoxic/anaerobic conditions and associated with high denitrification. Apart from process design, influent wastewater characteristics affect protozoan community structure. Aspidisca cicada was associated with low dissolved oxygen and low nitrate concentrations, while Trochilia minuta was indicative of good nitrifying conditions and good sludge settleability. Trithigmostoma cucullulus was sensitive to ammonia and phosphate and could be useful as an indicator of high effluent quality. The association rating assessment procedure of Curds and Cockburn failed to predict final effluent biological oxygen demand indicating the method might not be applicable to treatment systems of different designs.

PhD Student Wins Award

Congratulations to PhD Research Student Theresa Hughes of the water Technology Research Group, who won the best student paper award at the 2011 national meeting of the American Society of Mining and Reclamation held at Bismark in the USA for her paper 'Co-treatment of acid mine drainage with municipal wastewater using the activated sludge process: preliminary treatability studies.'  The paper has been published in the conference proceedings: Reclamation: Sciences Leading to Success edited by Professor  R.I. Barnhisel, pages 283-305, published by the ASMR, Lexington .

Successful PhD candidate

Congratulations to our colleague Donata Dubber for successfully defending her PhD thesis ‘The effect of anoxia and anaerobia on protozoan communities in activated sludge operation.’ Dr Dubber has already published a number of research papers on her study including

• Enumeration of protozoan ciliates in activated sludge: Determination of replicate number using probability Water Research 43, 3443-52;
• Replacement of chemical oxygen demand (COD) with total organic carbon (TOC) for monitoring wastewater treatment performance to minimize disposal of toxic analytical waste J. Journal of Environmental Science and Health Part A , 45, 1595-1600;
• The effect of anoxia and anaerobia on ciliate community in biological nutrient removal systems using laboratory-scale sequencing batch reactors (SBRs). Water Research, 45, 2213-26;
• The influence of fundamental design parameters on ciliates community structure in Irish activated sludge systems. European Journal of Protistology, In press.

Some Thoughts on the E.coli Outbreak in Germany

I suppose the many hundreds of students who have attended my introductory lectures on wastewater treatment can attest to my call for the past thirty years for microbial standards to be placed on wastewater treatment plants, and in particular to focus more closely on pathogen removal during treatment.  Wastewater treatment plants, especially activated sludge reactors, are ideal places for new strains of bacteria and antibiotic resistance to develop.  Our simple barrier approach to pathogen control based largely on dilution of effluents and the disinfection of drinking water has served us well, but the reuse of wastewater effluents, contaminated surface and ground waters are all direct routes to the food chain.  While the source of the current outbreak of E. coli  in Germany remains unknown, we should not rule out the very high possibility of such a link.  The need for better operational management coupled with final effluent disinfection to deal with pathogen release from treatment plants must be put on the agenda for a revised Urban Wastewater Directive, where emphasis is placed equally on both environmental and public health protection. 

New Publication of Foam Potential Measurement

Accurate measurement of foaming at activated sludge plants can be subject to large variation. In this study foam measurements are reviewed and two approaches to foam potential assessment are compared. The paper, written jointly by Martin Fryer and Eoghan O’Flaherty of the Water Technology Research Group at Trinity College Dublin, is available on open access at Link.

The full reference is: Fryer, M., O’Flaherty, E. and Gray, N.F. (2011) Evaluating the Measurement of Activated Sludge Foam Potential. Water, 3(1), 424-444. doi:10.3390/w3010424. Free download

New Publication on Activated Sludge Protozoa

Donata Dubber, a PhD student with the Water Technology Research Group, has just published a paper on the effect of anoxia and anaerobia on ciliate communities in BNR systems. The key outputs of the study were: (i) aeration conditions play a major role in how protozoan communities develop; (ii) activated sludge ciliates display different tolerances to anoxia/anaerobia; (iii) short times of anoxia enhance protozoan community complexity; (iv) with anaerobic conditions protozoan community complexity and abundances decrease; and finally (v) to ensure optimum performance lengths of anaerobia should be as short as possible.  The research is funded by Science Foundation Ireland.

The full reference is: Dubber, D. and Gray, N.F. (2011) The effect of anoxia and anaerobia on ciliate community in biological nutrient removal systems using laboratory-scale sequencing batch reactors (SBRs). Water Research, 45, (6), 2213-2226.   doi:10.1016/j.watres.2011.01.015