Microsieve Technology Applied to Lagoon Wastewater Treatment Facilities

Abstract

Water resource recovery facilities such as wastewater treatment lagoons are under increased pressure to upgrade and improve their effluent quality due to increased loadings and increasingly stringent effluent targets and regulations. Lagoon technologies have inherent advantages for rural communities, however, this technology remains prone to effluent compliance issues. The upgrading of existing lagoons with economical, small footprint, low intensity technologies would enable rural communities to meet stringent regulations. A knowledge gap was identified with respect to economical, compatible, and appropriate technologies for the removal of solids from lagoon effluent, particularly with respect to modern microsieve technologies and their potential to guarantee solids effluent compliance of lagoon wastewater treatment systems. As such, the objective of this thesis is to study the performance of a microsieve technology, the discfilter system, as applied to lagoon wastewater treatment facilities and to study its potential to meet effluent solids concentration compliance. The study was performed at pilot scale, at the Casselman, ON, Canada lagoon wastewater treatment facility. The study quantified the solids removal performance of the discfilter system using various filter cloths at various hydraulic and solids loading rates. Moreover, the study determined related peripheral benefits of the discfilter system applied to lagoon facilities, specifically the removal of total phosphorus and algae from lagoon effluent. Two filter materials with pore-sizes of 10 µm and 5 µm were investigated across various hydraulic loadings of 4.0 to 9.2 m/h and solids loadings of 15.7 to 574.1 g-TSS/m2 /h. The performance assessment highlighted a maximum hydraulic load of 6.85 m/h for the 5µm filter cloth, with the 10 µm filter cloth not showing hydraulic limitation within the applied hydraulic loadings of this study. The 10 µm filter cloth solids removal performance was dependent upon the operation of the upstream lagoon facility, particularly on the application of the aeration system. The 10 µm filter cloth demonstrated a solids removal performance that meets current federal Canadian total suspended solids concentration regulations (<25 mg/L) for all data sets studied during nonaerated operation of the final lagoon cell of the upstream lagoon facility. However, the 10 µm filter cloth showed susceptibility to changes in solids characteristics during aeration of the final iii lagoon cell, with 80% of the total suspended solids concentration data being non-compliant (>25 mg/L). The solids removal performance of the 5 µm material achieved a high effluent total suspended solids quality (<10 mg/L) in all conditions. The assessment of peripheral benefits showed total phosphorus removal from influent concentrations of 0.3 to 0.8 mg-P/L to levels at or below 0.3 mg-P/L. In addition, the discfilter maintained an effluent algae/Chlorophyll α concentration of 7 µg-Chl.α/L or less for influent concentrations ranges of 4 to 24 µg-Chl.α/L.