Treatment of Dairy Farm Effluents Using a Settling Tank and Reed Beds: Performance Analysis of a Farm-Scale System

Abstract

Effluents from intensive dairy farming should be treated to prevent water pollution. A full-scale integrated treatment system was developed at Poisy in the French Alps. The treatment system consists of an aerated settling tank followed by vertical-flow reed beds planted with common reed. Recirculation of reed bed effluent to the settling tank was used to reduce the concentrations of pollutants within the system. Dairy farm effluents included dairy manure, milk house wash water, manure storage runoff, and at times small amounts of waste milk. Mean inflow rate for milk house wastewater was 5,000 L d-1 (+50 L of waste milk). During periods of heavy rainfall, inflow rates of up to 35,000 L d-1 were observed due to runoff from yard areas. To improve treatment performance, an aeration system was installed in the settling tank in May 2006. Mass removals increased by more than 10% for organic pollutants due mainly to aeration. Mean load removals ranged from 82% to 96% for organic and solid pollutants. Mean total nitrogen and phosphorus removals were 76% and 19%, respectively. Sludge accumulation on the reed beds was 2.2 cm year-1. Sludge quality conformed to French land application regulations.