Effect Of Ions On Clogging And Biofilm Formation In Drip Emitters Applying Secondary Sewage Effluent

On-site drip irrigation experiments that were continued for 54days with a daily operation of 12h with sewage effluent and groundwater application were conducted to investigate the effect of two typical ions (Fe2+ and Ca2+) on emitter clogging. At the end of the experiment, several representative emitters were sampled to investigate the clogging mechanism through measuring the dry weight of biofilm substances (DW) and analysing the mineral constituents of clogging solids and the extracellular polymeric substance (EPS) of attached biofilm. The plain emitters demonstrated significantly better anti-clogging performance than the labyrinth emitters. For sewage application, the ions added increased the EPS and DW compared with sewage without ions added. Moreover, clogging in the labyrinth emitters increased with an increasing ion complex and concentration. Different irrigation water qualities produced similar mineral constituents of clogging solids: quartz, Ca+Mg carbonate, silicate, and iron oxide. However, the clogging risk and inducing mechanism varied with the types of ion added. Fe2+ promoted production of microorganisms and precipitation of solid particles, increasing the risk of biochemical clogging, while Ca2+ mainly caused chemical precipitation. A complex of Fe2+ and Ca2+ increased the risk of biochemical clogging under sewage application, while it caused chemical clogging for groundwater application. Therefore, the strategies for protecting emitter clogging should be developed through comprehensively considering water quality and emitter type used. Copyright (c) 2017 John Wiley & Sons, Ltd.