The utility of drip Irrigation for the distribution of on-site wastewater effluent
On-site drip irrigation of treated wastewater has been suggested as an alternative where traditional wastewater treatment methods are not available or not appropriate. Emitter clogging is a major concern when irrigating wastewater. Investigating emitter clogging is important to ensure the long-term success of drip irrigation systems distributing wastewater. Four types of drip irrigation emitters distributed influents of different qualities. The experimental emitters were specifically designed for use with treated wastewater. The control emitters were not. The emitters distributed tap water, primary septic tank effluent and secondary sand bioreactor effluent. Each effluent was distributed through each emitter type for ten minutes every six hours, seven days a week for twelve months. Emitter flow rates were measured each month to identify clogged emitters. The control emitters exhibited the greatest reduction in flow rates and were detectably different than the experimental emitters. The experimental emitters were not detectably different. Emitter clogging was gradual and incomplete. Flow rates fluctuated over time. Many of the clogged emitters recovered to near their original flow rates as time progressed. The emitters distributing the septic tank effluent exhibited the most significant reduction in flow. The sand bioreactor, which reduced the effluent 5-day biochemical oxygen demand from 147 mg/l to 0.5 mg/l and total suspended solids from 55 mg/l to 3 mg/l, also reduced the degree of clogging in all four types of emitters. Biofilms were analyzed to determine their influence on emitter performance. ATP measurements revealed that the emitters distributing septic tank effluent contained higher amounts of biomass than those distributing both tap water and sand bioreactor effluent. The ATP measurements did not show a strong correlation with flow rate reduction, therefore biofilms were not shown to be the cause of emitter clogging. The results of this study show that wastewater quality was a determining factor in emitter function. Secondary treatment of influent wastewater reduced the incidence of emitter clogging. Wastewater quality was a determining factor in biofilm development. Secondary treatment of influent wastewater reduced the extent of biofilm development in the emitters. After one year, the three driplines designed for irrigating wastewater were functioning as designed.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:atp luminescence drip irrigation emitter clogging sand bioreactor wastewater
Date of Publication:01/01/2004