Inclined Tubes Clarifier for Effective Removal of Suspended Solids from Canal Water Prior to Groundwater Recharge

Abstract

Groundwater recharge, through surplus supplies of canal water, may prove to be an important strategy for replenishing the rapidly depleting groundwater in Punjab and managing sustainably the groundwater resources. However, presence of suspended silt load in the canal water results in clogging of recharge wells and subsequent reduction in recharge rates and capacity of filters. In present study, an inclined tubes clarifier having filtration capacity of 1.8 L s-1 was designed and fabricated to filter the silt-loaded canal water. In the clarifier, tubes of poly vinyl chloride (PVC) media of 1-m length were attached one over the other to form an inclined honeycomb like structure through which canal water enters as inflow from the bottom and the clarified water exits as outflow from the top of the clarifier. Efficacy of the designed clarifier was tested at different total suspended solids ranging from 500 to 3000 mg L-1 in the canal water and at pumping rates varying from 0.3 to 2.1 L s-1. The results revealed more than 85% sediment-removal efficiency of the clarifier at flow rates above 0.8 L s-1. The results further indicated that efficiency of removing total suspended solids (TSS) reduced drastically at inflow rates more than 1.2 L s-1. Also, at all the flow rates, the efficiency was 6% higher for water samples having TSS more than 2000 mg L-1 in comparison to samples having TSS less than 1000 mg L-1. The clarifier makes no significant difference to the values of total dissolved solids, electrical conductivity, total solids and pH of the canal water.