Uniformity of Domestic Wastewater Effluent Application in a Subsurface Drip Distribution System

An on-site wastewater treatment project with two separate drip fields was operated for 6 years and received no maintenance. The two drip fields (with different design configurations) contained pressure-compensating emitters (PC) and non-pressure-compensating emitters (NPC), respectively, and received wastewater with an average 5-day biochemical oxygen demand concentration of 23 mg/L. Flowrates of the PC emitters reduced from rated average of 3.50 to 1.00 L/h, and the average flowrate of the NPC emitters reduced from 2.00 to 1.53 L/h. The statistical uniformities were 48 and 71%, and the uniformity coefficients were 70 and 86% for PC and NPC emitters, respectively. Significant, but incomplete, recovery was achieved with field-flushing and consecutive shock-chlorination treatments of 500 and 1000 mg/L.