Membrane separation techniques and their domain of application

pressurized membrane filtration: operation with prevention of fouling

Hollow fibers

ultrafiltration unit, Vigneux 55000 m3/day

PathogensUV dose mJ/cm2

4log 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 SA11 36

water disinfection by UV irradiation

• requires that all inland and 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

European Water Framework Directive 2000/60

Phosphate removal

BNR plants

Discard phosphate anaerobically

Luxury aerobic uptake of P in aerobic stage

Process adaptations for N and P removal

Anaerobic

Anoxic Aerobic

AirWastewater

EBPR plants

(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 poly-hydroxy-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 (polyP) 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).

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.

Enhanced biological phosphate removal (EBPR)

the principle

Degassing

Pressurized air

Anaerobic

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 precipitationmore sustainable, because it involves nutrient recovery

1 - Agitator2 - Flocculator3 - Settler4 - Raw water in5 - Settled water out6 - Purge

Nitrogen removal

Nitrification (Nitrosomonas and Nitrobacter)

NH3 + O2 NO2- NO3

-

Denitrification

NO3- + organics CO2 + N2

Process adaptations

Anoxic Aerobic

Air

Ammonia stripping• Two-step physical-chemical method• Step 1: Raise pH 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

Biostyr process (OTV)

polystyren foamlow-density microbeads 3 to 4 mm diameter

In the 1990s, researchers discovered that there could be other biologicalprocesses other than nitrification/denitrification that are able to remove nitrogen fromwastewater. The phenomenon of anaerobic ammonia oxidation was observed and thescientists at TU Delft identified the organisms responsible for the process to be from thePlanctomycetes family. With this information, TUD Prof Van Loosdrecht designed an innovative process – Anammox (ANaerobic AMMonium OXidation) processwhich converts ammonium to harmless nitrogen gas

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%.

NH4+ + NO2

- N2 + 2H2O

Anammox process