The investigation of the advanced treatment of municipal wastewater by modular flotation-filtration systems and reuse for irrigation

Abstract

The objective of this study was to provide clarified municipal wastewater effluent at the turbidity level of less than 2.0 NTU and reuse for landscape irrigation (golf course). For that purpose, during pilot -study first was used a combined flotation-filtration module-clarifier alone (Alternative I). A particularly designed configuration of the primary flotation unit and combined flotation-filtration clarifier, as a modular clarification system was used in the next step of the investigation (Alternative II). In addition, start up of the full scale plant was performed as well. In the first phase of this study, the impact of the type and concentration of coagulant and flocculant was tested. As a result, mechanisms of flocculation were proposed. Only under the moderate hydraulic loads (75.7-151.4 LPM) during pilot tests by Alternative I, was it possible to reach satisfactory turbidity reduction. By the Alternative II, the clarification performance was improved under the higher hydraulic load (302.8 LPM). The kinetics of the investigated flotation systems were assesed by empirical flotation models. Based on the pilot-study, Alternative II is recommended in order to reduce the high solids loadings under a higher hydraulic load, and it provided irrigation water at a required rate of 3785 m3/d during start up and optimization of the full scale plant.