IMPACT OF WASTE WATER TREATMENTS ON REMOVAL OF NOROVIRUSES FROM SEWAGE. 1 March 2012

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1 IMPACT OF WASTE WATER TREATMENTS ON REMOVAL OF NOROVIRUSES FROM SEWAGE 1 March 2012

2 Impact of wastewater treatments on removal of noroviruses from sewage defra project reference WT0924 Elaine Connolly, project manager, defra Roderick Palfrey, WRc plc, Swindon, Wiltshire Project period October 2010 May 2011

3 Background to the research Increasing industry and food safety concerns about norovirus Little known about norovirus in the natural environment Initial research to look into the scale of the problem

4 Norovirus in the Environment NV single stranded RNA virus CDC National Center for immunisation and respiratory disease Source human type, commonly cycles through shellfish, then by human crossinfection, returning to sewage (and other wastes) Major risk to elderly and other immunocompromised populations Commonly known as the winter vomiting bug

5 Objectives Measurement of Norovirus gene template in crude, storm and treated sewages Determine significance of treated effluents on total load discharged Determine reductions in Norovirus by different treatment process trains Investigate correlations between removal of faecal indicators, in particular coliphage, and attenuation of Norovirus by treatment processes Note: There are estimated to be 1 million cases of Norovirus infection in UK each year. The infective dose is 1-10 particles. Shellfish, being filter feeders, concentrate NV out of seawater if it is present. Shellfish are a source of human NV infection, hence the importance of wastewater discharges into shellfish waters. Settled sewage was sampled as a surrogate for storm overflow. NV cannot be enumerated by cultural methods so reverse transcription PCR was used, however this really only shows whether NV is or has been present; it does not distinguish infective from non-infective, just the presence/absence of NV DNA. [TE]

6 Sampling from sewage treatment Storm tanks Crude / influent sample Primary effluent / storm sewage surrogate sample Secondary effluent sample Final / tertiary effluent sample

7 Sampling 5 works (3 coastal) Advanced activated sludge High rate activated sludge Biological (percolating) filter Chemically aided settlement (CAS) + biological aerated flooded filter (BAFF) Membrane bio-reactor 70 samples between November 2010 and February 2011

8 Sample locations and numbers (1) Influent Primary Advanced activated sludge Filter Effluent Influent High rate activated sludge UV

9 Sample locations and numbers (2) 5 3 Primary Biological filter CAS Biological aerated flooded filter (BAFF) UV 4 Membrane bio-reactor

10 Measurements Norovirus RNA genome using threshold cycle count VeroMara at Scottish Marine Institute, Dunstaffnage Faecal indicators E.coli, total coliforms F+ & somatic coliphage Samples to NLS (National Lab Service) Works operation indicators BOD, suspended solids

11 Hypotheses and principles Primary settlement can model storm tank performance Norovirus behaves as bacteriophage (F+ and somatic) in terms of physical removal Norovirus activity cannot be measured Membrane bioreactor (MBR) treatment likely to reduce concentrations of norovirus significantly UV treatment is not expected to affect norovirus measurement

12 Range of norovirus concentrations Influent sewage Secondary effluent Final effluent ASP advanced ND 2170 ND ASP high rate ND 341 ND 431 ND 354 Percolating filter ND 3818 ND 382 Biological aerated filter, BAF Membrane bioreactor ND 340 ND 407 ND ND 708 Measurements all as genome copies / ml; ND = not detected in 10 mls; sensitivity

13 1e refers to primary treatment; 2e refers to secondary treatment (activated sludge, percolating filters, biological aerated filters, and membrane bioreactors; Microbial determinand concentrations 3e refers to tertiary filters (carbon filters at one works only) and to ultra-violet (UV) disinfection treatment at 2 works.

14 F+ phage concentrations

15 Norovirus concentrations

16 Removal rates across works

17 Norovirus concentrations by individual stages 1e refers to primary treatment; 2e refers to secondary treatment (activated sludge, percolating filters, biological aerated filters, and membrane bioreactors; 3e refers to tertiary filters (carbon filters at one works only) and to ultra-violet (UV) disinfection treatment at 2 works.

18 Correlation between faecal indicators

19 Correlation between F+ and norovirus

20 Findings Sewage treatment reduces Norovirus load Treatment process types may significantly affect removal of norovirus Activated sludge processes and Membrane Bioreactors most effective Filter processes may have differential effects between bacterial and viral indicators Norovirus analysis is complex individual values in this study were inconsistent with related samples Some indication that F+ phage could be a surrogate for treatment effectiveness Within this study difficult to identify effectiveness of individual treatment stages

21 Summary of Norovirus data Concentrations of Norovirus at different stages in sewage works samples showing average, standard deviations and maximum and minimum values

22 Final thoughts.. Replace percolating filters with activated sludge plants or membrane bioreactors? Build new works to accept all sewer flows? Costs for new works (10 million population) Energy costs increase 5 10 fold New build 1 3 billion Operating costs increase Greenhouse gas emissions double

23 Costs of changing works Cost for works Costs for works of 20,000pe change, for total Sustainability 1 million pe factor PercFilt to PercFilt to PercFilt MBR ASP MBR ASP Energy, MWh/a ,000 8,250 Sludge, ,950 6,550 tonne/a CAPEX, m OPEX, k/a , Greenhouse gases, tco 2 eq, 25years 9,852 18,942 14, , ,000

24 Related work Other work has been carried out by CEFAS for the FSA at a single site over a two year period. Findings include seasonal effects, and persistence of Norovirus at long distances from discharges

25 Thank-you Report now on the Defra web-site: With thanks to the staff and management of the host sampling sites (Thames, Wessex, Southern, South-West Water) Questions? Comment from meeting: Since CSO discharge is inevitable, the wastewater collection and treatment system can never be a Critical Control Point (in a HACCP, Hazard Analysis and Critical Control Point protocol) for controlling norovirus in seafood because by-pass is inevitable. In addition apparently 2% of properties have misconnection of foul wastewater to surface water drainage (as high as 10% in some areas) which is another by-pass. Irrespective of investment, the wastewater system can never be a CCP for norovirus in seafood. [Tim WRc Evans] plc 2012