Helminth eggs removal by microscreening for water reclamation and reuse

Abstract

Irrigation with reclaimed water is becoming a practical alternative to conventional irrigation in semi-arid areas of the Mediterranean like Spain, but it requires a reliable treatment process to provide a safe water supply. Helminth eggs are one of the main concerns for the safe use of reclaimed water, as they can survive adverse environmental conditions and they are highly infective. Spanish water quality criteria and International guidelines set a limit of 0.1 eggs/l for water uses with unrestricted human exposure. Two microscreening processes have been tested to determine their potential for helminth eggs removal, after a conventional physic-chemical reclamation process. Hydrotech Drum and Discfilters, provided with 10 microm pore size filter cloth, were tested to determine their efficiency for helminth eggs straining. An experimental test was conducted using 20 microm spherical latex particles, as surrogates for helminth eggs, to test the removal efficiency of a small full-scale drumfilter. In a subsequent laboratory test, actual Trichuris suis eggs were strained using a 10 microm pore size filter cloth from a discfilter. Results from both tests indicate that drum and discfilters are able to achieve 99% removal efficiency for spherical latex particles and a complete removal for helminth eggs in reclaimed water.