A large residential College in the north of England housing 550 live-in students and 450 non-resident staff operates its own on-site effluent treatment plant to treat all foul waste arising before discharge to local sewer. The effluent plant constructed in 1991 comprises an inlet settlement tank at the head of the works from where the clarified influent feeds by gravity the coke filtration biological treatment zone via a 4-arm rotating sprinkler unit. From here the biologically treated effluent flows via humus tanks to the final effluent chamber from which samples are taken for Discharge Consent compliance testing.
A review of historical performance data reveals that of 35 samples analysed during the period Nov 1999 to Dec 2005, the treatment plant failed to meet Consent on 8 occasions. Of those non-compliances, 6 were attributable to elevated ammonia, 1 to BOD and 1 to s/s.
At the time Cleveland Biotech was appraised of the situation, discussions and already taken place with a Contractor for the design and installation of a replacement treatment works with a higher biological capacity. However the anticipated costs of the build were considerable and taking into account the fact that from a mechanical point of view the existing plant was sound, alternative lower cost solutions to the problem were sought.