APPLICATION OF FLAT PLATE SOLAR COLLECTOR FOR THERMAL DISINFECTION OF WASTEWATER EFFLUENTS

Received; revised; accepted Application of solar energy for wastewater treatment has shown to have the least negative effects and costs. This experimental research was carried out in pilot-scale on the effluent of the extended aeration activated sludge wastewater treatment system in Kashan. The plant is located at the Kashan University of Medical Sciences campus and receives about 100 m3/d sewage from official and residential building blocks. In this study thermal disinfection of the effluent in 55 ºC for 2 hours using flat plat solar collector (FPSC) was investigated. During the study in the beginning of every week, one day was selected randomly and the pilot was run. The pilot influent temperature was the same as ambient air throughout the day. If the liquid temperature within the pilot increased above 55 ºC, a thermostatic valve opened. Passed liquid was maintained for 2 hours in this temperature. Whenever the volume of disinfected effluent was measurable fecal MPN test and Nemathoda eggs count-up were done according to the Standard Methods and Leeds-II directions, respectively. In 200 days from April to November the geometric mean of fecal coliform never exceeded the WHO guideline (1000 MPN/100mL), but in 5 days (21 % ) it exceeded the Iranian standard (400/100mL). Mathematical mean of Nemathoda eggs was less than 1 per liter (Engelberg Index) persistently. The mean of hydraulic loading rates was calculated 83.25 L/d m2 while it decreased to 41.85L/d.m2 in the days without thermal reclamation