Treatment of Cheese Processing Wastewater by Ridge and Furrow Disposal – Nitrogen Transformations

Objectives: This project was undertaken to determine the nitrogen transformations in wastewater from two dairy products industries as it percolated from the furrows to the groundwater. Ridge and furrow land treatment effectiveness was evaluated under various soil and loading conditions. Operation, maintenance and accuracy of the monitoring equipment used were also studied.

Background/Need: A ridge and furrow land treatment system consists of a series of ditches which allow for the distribution, infiltration and treatment of wastewater. Two ridge and furrow systems were studied: a cheese factory in Brodhead, Wisconsin which discharged an average of 39,500 gallons per day (gpd) of wastewater, and a creamery in Mindoro, Wisconsin which discharged an average of 14,000 gpd of processing wastewater.

Methods: Groundwater monitoring wells and lysimeters were installed and soil grab samples taken during the initial soils borings. Flow composited influent wastewater samples were collected monthly. Furrow samples were taken during intensive sampling periods at Brodhead in October and Mindoro in November of 1984. Samples were also collected routinely from the wells and lysimeters.

Wastewater, furrow, lysimeter, groundwater and stream samples were analyzed for biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), chlorides (Cl^–), total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH_3-N), nitrate and nitrite nitrogen (NO_3-N+NO_2-N) and pH. Soil and plant samples were also analyzed. Other monitoring included observation of load/rest cycles, reading monthly groundwater and surface water elevations, taking monthly 30-day average wastewater flow readings, cutting periodic grass samples during the growing season to determine nitrogen uptake and performance of infiltration studies to determine unsaturated zone flow rate.