The MBR Book: Principles and Applications of Membrane

Main permeate
header
Permeate pump
ZeeWeed ® membrane
cassettes
Air separator
Air header
Figure 5.26 A single train of 16 cassettes
Permeate header
Case studies 239
the on cycle), equating to a SAD m of 0.29 Nm 3 /h per m 2 . This is sufficient to maintain
a mean net flux of 17–19 LMH and a TMP of 0.1–0.2 bar, yielding a permeability of
�144 LMH/bar. The SAD p is thus 15–17 m 3 air per m 3 . The typical totalised flow
through the membrane per month is �1Mm 3 , and the typical maximum totalised
daily flow of �40 800 m 3 .
Maintenance cleaning in situ is conducted weekly using 500 mg/L NaOCl at pH
8–8.5. The chemical is back-pulsed slowly through the membrane, whilst still
immersed in the mixed liquor, for a period of 45 min. Only two recovery cleans, that
is ex situ chemical cleaning by soaking the membranes in 1000 mg/L NaOCl for 6 h,
were performed over the first 30 months of operation, with none conducted over the
first year.
To date, there have been no operational problems with this plant, other than one
foaming incident which demanded dosing with anti-foaming agent during the first
2 months during start-up of the system (Côté et al., 2004). Effluent quality has met
or exceeded expectations for SS, BOD, Ammonia-N and TN. The high-quality MBR
effluent is blended with effluent from the conventional trains A and C, allowing the
overall plant to meet present discharge standards. The MBR effluent quality is also of
high-enough quality to be considered for reuse as irrigation water.
5.3.1.3 Nordkanal wastewater treatment works at Kaarst
Background and plant description The plant at Kaarst in Germany, owned and operated
by the Erftverband (Erft Association), treats wastewater from the nearby towns of
Kaarst, Korschenbroich and Neuss. It was installed and commissioned in January
2004 following the success of the group’s first MBR plant at Rödingen, a smaller plant
which was commissioned in 1999 (Table 5.14). As of November 2005, the Kaarst
plant was the largest MBR plant in the world, with a population equivalent of
80 000 and a capacity of 48 MLD.
The site has five buildings which, respectively, house the sludge mechanical dewatering
process, the fine screens, the coarse screen, the MBR and the process controls.
Additional installations include lidded sludge and sludge liquor holding tanks, a grit