For COD determination closed reflux, calorimetric method included digestion at 150 C for 2 h in COD vials followed by spectrophotometer reading at 530 nm (APHA, 2005). The pH was measured using a digital pH meter (HANNA, HI 991003 Sensor Check pH), TDS and conductivity by HANNA, HI9835 Microprocessor for conductivity/TDS. At least three readings were taken for each parameter each time and then mean value was calculated.