REMOVAL OF ORGANIC MATTER IN WASTEWATERS OF A MILK FACTORY AND A HOSPITAL USING A CUBIC LATTICE BASED ROTATING BIOLOGICAL CONTACTOR IN VIETNAM

Abstract

Pilot tests of a cubic-lattice-based rotating biological contactor were implemented to remove
organic matter from wastewater from a milk factory and a hospital in Vietnam. In the milk factory
wastewater, the biochemical oxygen demand (BOD) removal ratio was stable between 60% and 90%
(average 75%) using this method, with a BOD surface load of 0.002–0.020 kg•m−2•day−1. The average
nutrient ratio of the raw wastewater was 0.13 of total nitrogen and 0.015 of total phosphorus compared with
1.0 of BOD. The BOD of treated water was less than 50 mg•L−1, achieving category B of the industrial
wastewater standard of Vietnam (QCVN 40:2011). For the hospital wastewater, the BOD removal ratio was
stable between 60% and 90% (average 78%), with a BOD surface load of 0.005–0.022 kg•m−2•day−1. The
average nutrient ratio of the raw wastewater was 0.25 of total nitrogen and 0.018 of total phosphorus
compared with 1.0 of BOD. The BOD of treated water was less than 50 mg•L−1, satisfying category B of the
medical wastewater standard of Vietnam (QCVN 28:2010/BTNMT). The electric power consumption was
0.73 KWh•m-3 of wastewater. The sludge conversion ratio from BOD was 0.51 kg TSS•kg BOD−1 based on
the excess sludge and suspended solids in raw wastewater and treated water.