PERFORMANCE EVALUATION OF SOLAR DISINFECTION AND CARBON NANO-MATERIALS FOR REMOVAL OF MICROPOLLUTANTS IN TREATED EFFLUENT FROM NUST SECONDARY TREATED WASTEWATER

Abstract

Pakistan’s water availability per capita is decreasing, thus turning the conditions from water scarce to water stressed, and the issue is worsening due to increasing havocs of the climate change and environmental degradation. Thus, in order to meet the water demands of the nation, there is a need for water recycling and reuse, and for water management to decrease the water stress conditions. The MBR and phytoremediation plants located at NUST H-12 sector, Islamabad, are aimed at wastewater treatment to recycle and reuse it horticulture purposes. However it is not obvious if the treated effluent is safe for reuse this study aims to seek the answer for this question. This study starts with the screening of organic micropollutant in treated effluent using innovative passive sampling techniques. then, the removal of detected micropollutants in the effluent was evaluated using conventional adsorbent and emerging adsorbent. In order to test the capability of the adsorbent for emerging contaminants sulfamethoxazole (SMX) was used as model contaminant alongside these adsorbents a parabolic trough collector were also evaluated The Gas chromatography- Mass spectrometry (GC-MS) analyses of low density polyethylene (LDPE) passive sampler that were deployed in storage tank of membrane bioreactor and phytoremediation plant for 15 days indicate the presence of several micropollutants. The sorption results indicate that neutral micropollutants can be removed up to 99.2-99.8% and 84.76%-89.46% respectively through carbon nanotubes and graphene oxide, while conventional adsorbent provided removal efficiency 69.10-74.09%. For pharmaceutical drug sulfamethoxazole, the activated carbon and carbon nanotubes showed removal efficiency of 66% and 68% respectively at 15mg/L for 1ppm solution at pH 6.5.The slightly less removal percentage may be attributed to the fact that at environmental pH the SMX is in ionized form. For removal of phosphates and sulphate, carbon nanotubes proved to be more efficient adsorbent than graphene oxide and activated carbon with removal percentages of 85-90% at flow rate of 1 mL/min with increasing flow rate adsorption capacity decreased for all the adsorbents. Alongside these adsorbents the performance of parabolic trough collector (PTC) was also evaluated for removal of phosphate and sulphates. The PTC did not show significant effect on the removal of ionized species. In this study, I realized the effluent is a very complex system which contains hundreds of thousands of micropollutants. For such a complex system, I screened 125 stationary phases for the optimum separation of nitrogen-contatining heterocyclic aromatic organic micropollutants for comprehensive two-dimensional gas chromatography (GC × GC).I also identified a set of two columns appropriate for estimating environmental properties. 2 Taken together this study highlights that the treated effluent is not safe for reuse without further polishing. A combination of sorption based technique and PTC can act as appropriate polishing unit. The GC×GC columns should be evaluated experimentally for their performance to separate complex mixture of micropolluatants and estimate their properties. . Key words: MBR, Phytoremediation Plant, Organic Micropollutants, Carbon Nanotubes, Activated Carbon, Graphene Oxide, Physicochemical Parameters, Pharmaceutical drug, Risk assessment