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

Abstract

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.