INVESTIGATING REMOVAL OF PESTICIDES FROM WATER BY NANOFILTRATION MEMBRANE TECHNOLOGY

Abstract

Agricultural activities form the backborne of Kenya´s economy. Inorder to control crop losses, pesticides are used and in the recent past, more of the pesticides have been used to increase production. However,  the effect of pesticides on the environment is very complex as undesirable transfers occur continually among different environmental sections. This eventually leads to contamination of drinking water sources  such as rivers and  lakes located near active agriculture areas, including  flower farms around Lake Naivasha where poisoning of lake water by pesticides caused fish deaths. The aim of this paper was to investigate application of nanofiltration membrane technology in the removal of pesticides  from water. A pesticide, atrazine was selected for the study  due  to its extensive  use  in controlling weeds and the adverse environmental effects associated with it.  Membrane filtration was used using a laboratory scale crossflow filtration units that operated in total recycle mode to ensure even concentration of atrazine in the feed solution to seperate atrazine form water. Concentration of atrazine in aqueous solution was analyzed using high performance liquid chromatography (HPLC). Retention of atrazine by four nanofiltration membranes i. e. NF90, NTR7250, and NF270 was investigated.  The effect of feed solution pH, concentration and feed pressure were investigated, as was the effect of humic substances and titanium dioxide catalyst on retention by membranes. pH and feed pressure showed influence on retention of atrazine while initial feed concentration had little influence. The presence of HA led to  improved atrazine rejection efficiency but led to flux decline on all membrane tested while TiO2 led to high rejection efficiency and low flux decline. Of all four membranes, NF90 showed the best performance in retention of atrazine in water while NTR7250 showed the least. This indicated that with proper membrane selection, its possible to treat water contaminated with pesticides to acceptable levels.