Jl. Jansen et al., HANDLING OF ANAEROBIC DIGESTER SUPERNATANT COMBINED WITH FULL NITROGEN REMOVAL, Water science and technology, 27(5-6), 1993, pp. 391-403
Citations number
8
Categorie Soggetti
Water Resources","Environmental Sciences","Engineering, Civil
In order to meet future standards Of 8 Mg/l total-nitrogen, 0.3 mg/l t
otal-phosphorous and 10 mg/l BOD7, the Klagshamn wastewater treatment
plant in Malmo has to be upgraded. A concept where the standards could
be met within the existing activated sludge plant has been found. Pri
mary precipitation is followed by a single sludge post-denitrifying pr
ocess where methanol is added as external carbon source. The system is
high rate with only 7 hours retention time in the biological reactor.
In order to improve the process stability and make a future increase
in load possible within the existing plant, handling of digester super
natant has been examined. The normal operation of the sludge handling
system leads to discharge of a supernatant with a high content of ammo
nium. The load from the supernatant made about 15% of the total-nitrog
en load on the plant on an average basis but could reach up to 65% dur
ing working hours. This extra load could be recognized as peaks of amm
onium and nitrate in the effluent. The digester supernatant and its im
pact on daily variations in ammonium and nitrate have been examined in
detail and the examination has formed the basis for a mathematical mo
delling of the system in order to test strategies for optimized handli
ng. Equalization of the supernatant flow, separate nitrification of th
e supernatant, and completely separate treatment of the supernatant ha
ve shown to be able to improve process stability. Flow equalization se
ems to be as effective as the two other more expensive and complicated
solutions.