Membrane separation techniques and their domain of application

pressurized membrane filtration: operation with prevention of fouling

Hollow fibers

ultrafiltration unit, Vigneux 55000 m 3/day

Pathogens UV dose m. J/cm 2 4 log inactivation (99. 99) Cryptosporidium parvum oocysts <10 Giardia lamblia cysts <10 Vibrio cholerae 2. 9 Salmonella typhi 8. 2 Shigella sonnei 8. 2 Hepatitis A virus 30 Poliovirus Type 1 30 Rotavirus SA 11 36 water disinfection by UV irradiation

European Water Framework Directive 2000/60 • requires that all inland coastal waters within defined river basin districts must reach at least good (ecological) status by 2015 • transboundary if necessary • defines how this should be achieved through the establishment of environmental objectives and ecological targets for surface waters • action plan to be published end 2009 by all Member States

Phosphate removal plants q EBPR BNR plants q Discard phosphate anaerobically q Luxury aerobic uptake of P in aerobic stage q Process adaptations for N and P removal Wastewater Anaero bic Air Anoxic Aerobic

Enhanced biological phosphate removal (EBPR) the principle Dry solids of conventional activated sludge have a total phosphorus contents of 1 - 1. 5 %, while those of enhanced biological P removal plants (based on a luxury-uptake process) can achieve up to > 4 % TP. (Melasniemi 2000) Under anaerobic conditions phosphate-accumulating organisms (PAOs) are not able to grow but can accumulate and store organic substrate by converting small organic acids into polyhydroxy-butyrate (PHB) and similar energy rich organic compounds. For this process the PAO bacteria need energy which they gain under anaerobic conditions from the conversion of stored energy-rich polyphosphate (poly. P) to dissolved phosphate which is released to the water under these conditions. When oxic conditions are met again, PAOs reconstitute their internal polyphosphate ‘batteries’ resources. This process is called luxury uptake (because the P uptake is then far higher than what would occur in usual biotreatment conditions).

Pressurized air Anaerobic Degassing This process will be illustrated by the technical visit of the biological wastewater treatment plant in Waterloo (compulsory visit for all, including EIB students).

To reach good nitrification rates, it is necessary to work at a low F/M ratio. The biomass concentration thus needs to be higher than in the conventional process. These requirements have consequences regarding the subsequent sludge manipulation options and disposal routes.

struvite precipitation more sustainable, because it involves nutrient recovery

1 - Agitator 2 - Flocculator 3 - Settler 4 - Raw water in 5 - Settled water out 6 - Purge

Nitrogen removal q Nitrification (Nitrosomonas and Nitrobacter) NH 3 + O 2 NO 2 - NO 3 - q Denitrification NO 3 - + organics CO 2 + N 2 q Process adaptations Air Anoxic Aerobic

Ammonia stripping • Two-step physical-chemical method • Step 1: Raise p. H to 10. 5 -11. 5 – convert ammonium ions to ammonia gas • Step 2: Air-strip – cascade wastewater countercurrent to air flow – ammonia gas escapes to atmosphere • Pro: less costly, no sludge or Cl by-products • Cons: acids/bases, scale, freezing problems

electron acceptor exothermic

Electron acceptors

polystyren foam low-density microbeads 3 to 4 mm diameter Biostyr process (OTV)

Anammox process In the 1990 s, researchers discovered that there could be other biological processes other than nitrification/denitrification that are able to remove nitrogen from wastewater. The phenomenon of anaerobic ammonia oxidation was observed and the scientists at TU Delft identified the organisms responsible for the process to be from the Planctomycetes family. With this information, TUD Prof Van Loosdrecht designed an innovative process – Anammox (ANaerobic AMMonium OXidation) process which converts ammonium to harmless nitrogen gas NH 4+ + NO 2 - N 2 + 2 H 2 O This process only requires the conversion of half of the ammonium to nitrite resulting in the reduced need for aeration, thus saving energy. The bacteria involved in the Anammox process will then convert ammonium and nitrite together into nitrogen gas without the need for any additional organic carbon compounds. Anammox is able to reduce carbon dioxide emissions by up to 90% compared to conventional nitrification / denitrification processes. It occupies up to 50% less space and reduces aeration energy by up to 60%.