Optimization of operation modes and improvement of operation conditions of surface runoff treatment facilities

Summary

Common drawbacks of packaged units for urban runoff treatment are considered. The task of the study was regulating and optimizing the operation modes of the existing facilities in order to improve the effluent quality to meet the standards. By the example of the unit that was most suitable for the generally accepted treatment process flow scheme the analysis of the operation of a laminar sedimentation tank module under design conditions was carried out. To determine the operation efficiency in the hydrodynamic mode physical experiments (by adding a chemically inactive tracer to wastewater being treated) and computer simulation were carried out. To upgrade the laminar sedimentation tank the chemical treatment stage was introduced into the process flow scheme. Adding coagulant provided for improving the treatment efficiency; however, the required concentrations of suspended solids in effluent downstream the sedimentation tank (10 mg/dm3) were not met. The efficiency of the sedimentation tank in hydrodynamic mode was improved by using stepped feed and distributed collection of wastewater in a modular unit as well as by using an air distribution system located in the lower central part of the laminar sedimentation tank module. This type of the design provided for coarse bubble aeration over the entire surface area of the chamber at the required mixing rate. The implemented design changes in the laminar sedimentation tank module resulted in the efficiency of urban runoff treatment before the further tertiary treatment meeting the regulatory requirements.

Key words

reagent treatment , lamella settler , computer modeling , urban runoff , packaged modular water treatment unit , hydrodynamic mode , air distribution system