Water quality parameters were measured at the laboratory of the Department of Environmental Sciences, Jahangirnagar University and in the laboratory of Bangladesh Council of Scientific and Industrial Research (BCSIR). Then the coagulation of the sample water using Tamarindus indica, Litchi chinensis and Dolichos lablab seeds were done in the laboratory of Bangladesh Council of Scientific and Industrial Research (BCSIR). Preparation of sample water The sample water used throughout the study was obtained from the Bangshi River, located near the Dhaka city. Water was collected during monsoon season. The raw water is stored in the plastic bottle in the laboratory of BCSIR, Bangladesh. Stock solution of poly-aluminium chloride (PAC) Poly-aluminium chloride (PAC) were used in this study was supplied by Department of Environmental sciences, Jahangirnagar University, Savar, Dhaka. 1% solution of PAC (1 g of PAC in 99 ml water) in tap water was made. Then the required concentrations were used for different dosages as coagulant aids. Preparation of coagulants Locally available dry Tamarindus indica, Litchi chinensis and Dolichos lablab seeds were obtained from local market. Seed pods were allowed to mature and dried naturally to a brown color on the tree. The seeds were removed from the pods and covered. The seeds were kept in room temperature in the home. The seed kernels were ground to fine powder using a mortar and then kitchen blender to make it of approximate size of 0.005mm to achieve solubilization of active ingredients in the seed. Then the powder was stored in the BCSIR laboratory.
Jar test operations Experiments were carried out in the laboratory of Bangladesh Council of Scientific and Industrial Research (BCSIR).The treatments were done by varying concentrations of Tamarindus indica, Litchi chinensis, Dolichos lablab seeds powder. Each treatment was conducted on the response of turbidity, pH, electric conductivity, total dissolved solids, COD and heavy metals such as Hg, Ni, Zn, Pb, Cd, Fe, Ca,Cr, Mn, Mg, Na. First the samples ought to be measured for turbidity, BOD, and COD for representing an initial concentration. The experiment was carried out in a jar test operations. It was carried out as a batch test. Before operating the jar test the sample were mixed homogenously. Then the dry seed powder was measured by digital balance. Coagulants of varying doses were added in the beakers. Sometimes there was replica of concentration to understand the errors. pH of the sample water was enough for this test. 1or 2 drop coagulant aid was used in the beaker. Then the beakers were agitated at various mixing speed using orbital shaker, which consist of rapid mixing for 15 minutes and slow mixing for 12-15 minutes using orbital shaker for mixing the sample with coagulant. Finally turbidity, pH, TDS, EC, COD was measured The coagulation- flocculation process consists of three distinct steps. First, the coagulant was added to the raw water and a rapid high intensity (200 rpm) mixing is initiated. Second, the suspension was slowly (40 rpm) stirred to increase contact between coagulating particles and too facilitate the development of large flocs. Third, mixing was terminated and the flocs were allowed to settle. Then filter paper was used for filtration. After filtration turbidity, pH, and conductivity, total dissolved zxEFsolids, COD were measured.
Determination of the Physicochemical Parameter of the Samples The Physicochemical Parameter of the samples was measured to determine the quality of the sample water before and after coagulation. Turbidity reflects the transparency of the liquid sample. The turbidity of the samples is also measured by turbidity meter HANNA H193703 MICROPROCESSOR TURBIDITY METER, range 0.00-1000 NTU (Nephelometric Turbidity Unit). Basically the meter works on light scattering method. The pH of water was measured by using a pH meter (Model No.1161795), COD was measured by closed refluxed colorimetric method (Model no. HACH 980 USA), BOD5 by dilution metlhod, heavy metals such as Hg, Ni, Zn, Pb, Cd, Fe, Ca,Cr, Mn, Mg, Na was determined by AAS (Model NO.Shimadzu AA-7000 series )