of 14 m 2 and a working depth of 5 m this tank was provided with an aeration system comprising a booster pump with a flow rate of 130 m 3 hour connected to an oxygen supply and diffusers located at the bottom of the tank to provide the rhodobacter capsulatus culture with 117 kg per day of oxygen the residence time of the effluent in the tank was 7 days the culture temperature was 30 u00b0 c and its ph was 6 9 under those conditions a biomass production of about 0 05 g of dry matter per liter per hour was produced namely a biomass production of about 100 kg of dry matter per day as for technique 1 the biomass was separated from the effluent by flotation using flotation equipment located downstream of the tank and supplied from the tank the concentration of the biomass collected after flotation was in the range 30 g to 60 g of dry matter per liter technique 2 reduced the initial nitrogen and phosphorous loads in the liquid manure by 48 and 69 respectively and the initial cod was reduced by 91 here again after a regulation storage period of at least four months the residual effluent could be spread on agricultural land to act as a fertiliser table 2.