Controlling Mechanism of Chlorination on Emitter Bio-clogging for Drip Irrigation Using Reclaimed Water

Author(s): Song, P.; Li, Y.; Feng, G.

Emitter clogging has been one of the bottlenecks restricting the drip irrigation application and promotion. Drip irrigation using reclaimed water or polluted surface water may causes the greater risk of bio-clogging, which is the most typical and complex clogging type. With the strong oxidizing effect, chlorination has been considered as the most effective method of controlling emitter bio-clogging. However, its mechanism is still unclear. Meanwhile, there were no unified standards established for chlorination to refer to. Field experiment using reclaimed water treated with Cyclic Activated Sludge System (CASS) process was carried out in the sewage treatment plant, in order to study the controlling mechanism and impacts on emitter bio-clogging with three types of chlorination modes. The results showed that the chemical chlorination could effectively regulate the microbial growth in the emitter clogging substances, with the microbial Phospholipid Fatty Acid (PLFAs) decreased by 8-36%, and the microbial types reduced by 2-3, and the microbial activity decreased by 3-23%, and the secretion of sticky Extracellular polymeric substances (EPS) decreased by 20-43%. The bio-clogging substances were well controlled, and the contents of solid particles (SD) decreased by 5-48%, while the discharge ratio variation (Dra) and Christiansen uniformity coefficient (CU) were improved by 15-23% and 7-20% respectively. However, the effects of different chlorination modes varied significantly, the chemical chlorination with low concentration and long contacting duration (2.5mg/L+2h) was recommended to control bio-clogging in the drip irrigation system using reclaimed water treated with CASS process.

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