A Study of Nitrogen Effluent Loads from Unlined Storage Ponds

Abstract

Animal wastes have been stored in unlined storage ponds. One concern is that nitrogen loads accumulated in soils would affect long-term water quality. At the A10 area in the Lake Kasumigaura basin, Japan, where pig production ranked high, field investigations were conducted in 1992 and 2002. Water quality and discharge in four sub-catchments were measured in detail. The nitrogen pollutant load was calculated using the unit pollutant load; the nitrogen effluent load was calculated using load-discharge regression curve. Consequently, in the sub-catchment, where pig production was ceased in 1990, nitrogen effluent loads from the retired unlined storage pond were 1.34×10₃kg·y^-1 (nitrate nitrogen load) for 1992 and 95kg·y^-1 (T-N load) for 2002. The effluent loads decreased 5% in terms of T-N load over 10 years. Furthermore, the calculated effluent rates in the sub-catchments, where pig production is performed currently, were approximately 40% for 1992 and 30% for 2002.