Laboratory methods
Total suspended solids were determined in accordance with the method outlined by APHA (1989). A known quantity (25 ml) of a well-mixed sample was filtered through a pre-weighed Whatman GF/C filter with a pore size of ~ 0.45 ~tm. The filters were then dried at 105 °C, cooled in a desiccator and weighed. The cycle of drying,cooling, desiccating, and weighing was repeated to ensure constant weight was obtained.Turbidity was measured using a laboratory turbidimeter
(ttach Model 2100A) and was expressed in NTU(Nephelometric turbidity units). A standard reference turbidity tube of 79 NTU was used at each time of operation as an additional measure of turbidity.All nutrients were determined using Hach reagents according to Hach protocols and standard methods (APHA 1989). Phosphorus analysis embodied two general
procedural steps, conversion of phosphorus to orthophosphate using acid hydrolysis (acid persulfate oxidation
technique) and determination of orthophosphate(ascorbic acid method). Total nitrogen was determined using a persulfate digestion method, nitrate using a cadmium reduction method, nitrite using diazotization method and ammonia using Nessler method (APHA1989). The calibration of all methods was determined with known standard solutions.