Evaluating the performance of clarification and ultraviolet units in disinfection of Isfahan North waste water treatment plant (WWTP) effluent in pilot plant

Usage of municipal waste water treatment plant (WWTP)، especially in agricultural applications، requires disinfection to standards level. Application of UV radiation due to fewer disadvantages in comparison with other disinfectants is being increased around the world. The aim of this study was to evaluate treatment and disinfection of Isfahan North Wastewater Treatment Plant effluent by clarification and UV radiation.

The combined system was used in series in pilot scale including: Clarifier + Low Pressure (LP) + Medium Pressure (MP) UV Lamps. Total coliform (TC)، fecal coliform (FC) and fecal streptococcus (FS) were analyzed as microbiological parameters in all effluent samples. TSS، iron، total hardness، absorbtivity and transmittance (%UVT) were tested as physicochemical parameters before and after of units.

Results of this study showed that the mean value of UVT in 254 nm and absorbance in clarified effluent were 34 percent and 0. 47 au/cm، respectively. In disinfection of clarified effluent with LP، MP، and combination of LP and MP lamps، doses of 400، 576 and 407 mws/cm2، the number of TC، FC، and FS was declined to standards of 1000 TC، and 400FC/100ml for effluent discharge. In addition، in doses of 400، 422 and 407، number of FS was reduced to 5 Log. Maximum regrowth of coliforms was seen after LP lamp and it was 7 percent. Maximum fouling on quartz sleeve was formed in TSS of 48mg/l، while concentration of iron and hardness was 0. 48، 249 mg/l، respectively.

Improving UV light penetration due to removal of coarse particles and flocks in clarifier، disinfection of clarified effluent with high irradiation time was possible in conventional doses. However، for upgrading the effluent quality and disinfection of high flow rate، using advanced treatment systems such as filtration is recommended.