Performance of different filter combinations with surface and subsurface drip irrigation systems for utilizing municipal wastewater

Abstract

Large volumes of wastewater (WW) are being generated worldwide as a consequence of rapid urbanization and growth of industries. The reuse of WW finds increased application in irrigation but the presence of toxic elements and microorganisms limits its use for irrigation purpose. To reduce the contamination of WW for irrigation, drip system is seen as an appropriate choice due to restricted quantity of water application. Emitter clogging is viewed as the main problem associated with drip system for its large-scale use with WW. Physical and chemical characteristics of WW were determined and compared with groundwater (GW). Higher EC, pH, Mg, and CO3 were observed in the GW but higher turbidity, total solids, HCO3, and Ca were observed in the WW. The population of total coliforms (2.72 × 104 to 5.2 × 107) and E. coli (1.8 × 103 to 2.64 × 106) were detected in WW. The hydraulic performance of drip emitters was studied for 2 years with WW and GW using sand media filter (F1), disk filter (F2), and combination of both filters (F3). Higher removal efficiency for turbidity, total solids, Ca, Mg, CO3 total coliforms, and E. coli was observed with combination filter. Emitter discharge exponent was also close to 0.5 with combination filter. Emitter flow rate decreased (in the sequence of F1 > F2 > F3) with increase in time of operation. After 2 years of operation under F3, coefficient of variation was less than 4 % with both WW and GW. Thus, it showed good performance in surface placed emitters but it was 7.2 % with WW and 9.5 % with GW under subsurface (15 cm) placed emitters. Clogging of emitters was controlled by flushing. Flushed emitters placed at 30 cm depth resulted in 3.7 % reduction in discharge as compared to 8.7 % reduction in the absence of flushing, under filter F1. Emitters with F2 produced least improvement in discharge.