Upgrade of horizontal sedimentation tanks with the use of dissolved-air flotation

Summary

The analysis of the efficiency of low turbidity colored water of the Vychegda River purification at the water treatment facilities of Syktyvkar in horizontal sedimentation tanks operating in the mode of coagulation at 2–3 times lowered hydraulic loading is presented. The necessity of upgrading the sedimentation tanks by redesigning their exit sections into flotation chambers is substantiated. The enhancement of the sedimentation tank operation by equipping with a flotation chamber provides for meeting the regulatory requirements to the drinking water quality under the conditions of significant seasonal fluctuations of the raw water quality indicators and temperature. Enhanced clarification of the water being coagulated is ensured before the filtration stage; at that the flow rate of backwash water decreases 3 times, the number of filter washes per day decreases to 0.5 times and less (filter run increases to 2 days and more). Backwash water purification together with raw water provides for streamlining the process flow scheme and chemical facilities (the number of chemical injection and dosing points decreases); facilitating the operation of the facilities, 8% operational expenses saving and plant demand decreasing to 3%. The upgrade of horizontal sedimentation tanks with the use of dissolved air flotation is more economically and environmentally feasible than the reconstruction of the two-stage filtration facilities. It provides for doubling the sedimentation facilities output, decreasing the amount of wash water and combined with raw water handling.

Key words

wash water , horizontal settling tank , filtration , pressure flotation , low turbidity colored water , hydraulic loading , water treatment plant