Experiments On Tube Settler For The Treatment Of Fbw And Optimization Of Plant Operation For Residual Reduction

Conventional water treatment plant generates two types of process wastes, filter back wash water and sludge. Characteristic studies of these wastes reveals that it contains high solids content, metals and bacteriological concentration, which are generally more than permissible disposable standards. Direct disposal of these wastes in to natural stream pollutes the receiving streams, affects human health on downstream users and violation of disposal standards. These wastes constitute considerable amount of water and direct disposal of filter back wash water causes wastage of these scare resources. Thus direct disposal of water treatment plant waste will affect the natural ecosystem. This study intends to develop a residual reduction and reuse plant for filter back wash water in conventional water treatment plant. The main objective of the present study is to reduce the amount of filter back wash water generated, by modifying the operational conditions of filter back wash and to know the potentiality of tube settler on the removal of FBW sludge. This study also encompasses the reuse of FBW sludge as a raw material for brick manufacturing. Optimization studies on filtration as well as back wash processes were conducted at Chavasseryparamba water treatment plant, Kerala and operational modifications mainly focused on the reduction of residual generated during back wash. Characterization of filter back wash water and sludge were carried out to assess the pollutant loading, degree of treatment and possible reuse options. Laboratory scale tube settler experiments were conducted to study the settling character of filter back wash water. FBW sludge has been characterized and the result of which reveals that, it contains metal oxides such as SiO2Al2O3, CaO, Fe2O3 and MgO.FWB sludge has mixed with brick earth for different proportions, molded to the standard brick dimensions and sun dried over a period of seven days. Results of optimization studies on the operation of rapid sand filter and its back wash shows that the optimum filter loading rate and filter run volume are found to be 8m/hr, and 560m 3 /m 2 respectively. With the above mentioned optimum operating conditions the filter back wash volume reduce up to 18%, Results of characteristic study of FBW reveals that filter back wash water contains high solid content and bacterial density of 53 NTU and 3286 MPN/ 100ml, respectively. Experimental studies on tube settler show that both theory of discreet particle settling and flocculent settling are applicable for the treatment of filter back wash water. From the tube settler studies, it is observed that optimum settling velocity of 6.40x10 -4 m/s is found to be more suitable for tube settler treatment of FBW water with recycle in conventio0nal WTP (effluent turbidity < 30 NTU).How ever if we need to treat the FBW water without passing through conventional treatment, i.e., directly passing the FBW water through tube settler along with disinfection process, then the ideal settling velocity through tube settler found to be 3.27 x 10 -4 m/s. At this velocity the effluent turbidity of the tube settler is found to be less than 10 NTU. Characteristics of FBW sludge reveals that it contains higher organic material (26.50%) and metallic oxides. Mineralogical studies reveals that sludge contain higher percentage of clay and silt(57%). Presence of metallic oxides and fine clay and silt particles make WTP sludge favorable for the usage in brick making, however, the presence of higher organic content limits the usage. The optimum sludge usage in brick making was found to be 25percent by volume. The compressive strength of brick made with WTP sludge are found to be on par with BIS requirements. Brick made with 25 % sludge have compressive strength of 111.65 kg/ cm 2 which comes under class10 of IS 1077(1992) which can be used for all type of construction. KEYWORD: Experiment, Tube Settler, Treatment Of Fbw, Optimization, Plant Operation, Residual Reduction