Håkan Jansson

Treatment of wastewater from milk rooms with ferric sulphate

Wastewaters from the milk rooms of dairy farms are rich in phosphorus (P) and in some parts of Finland, particularly in the rural north, they may locally account for a large proportion of the P load on watercourses. In this study, we tested the treatment of milk room wastewaters with ferric sulphate liquid (trade name Kemwater PIX-115) in batch experiments and on a practical scale at two farms. The concentration of dissolved reactive P (DRP) could be decreased by > 90% with relatively small amounts of the chemical (40 l/kg of reduced DRP); other P forms required higher doses. In the farm scale experiments, the chemical was dosed with an automatic pump, and the precipitate was separated 1) with straw/sandbed filtration on a farm with 35 cows, and 2) by sedimentaton on a farm with 70 cows. The systems were not very expensive to construct (6200 or 2500? per farm and 177 or 36? per cow, respectively). In this study, separation by sedimentation was more effective in reducing total phosphorus from the wastewater than filtering.