Cultus Lake Park Sanitary Sewer Infrastructure Assessment

Fraser Valley Regional DistrictCultus Lake Sanitary Sewer Infrastructure Assessment – Final ReportFigure 7: Moving Bed Biofilm Reactor (MBBR) Schematic4.4.5 Evaluation of Secondary Treatment ProcessesTable 9 summarizes the advantages and disadvantages of the secondary treatmentprocesses discussed in previous sections.Table 9: Secondary Treatment – Advantages and DisadvantagesAlternative Advantages DisadvantagesSequencing BatchReactors (SBRs)Rotating BiologicalContactors (RBCs)• Eliminates need for secondaryclarifiers and sludge returnpumping facilities;• Large flow variations can betreated• Low operational attention• Simple operation;• Eliminates need for sludge return;• Readily covered;• Lower power requirements.• Proven technology• Easy to operate• Covered units eliminate odorous• Complex control technology• Scum removal can be difficult;• Reliability of the decant mechanismhas been a concern in the past• Intermittent operation requires largeraeration systems, and a higherelectrical peak demand charge.• Maintenance more complex thanother biological processes• Downstream filteration or finescreening is required to prevent solidscarry over to disposal fields• Effluent equalization required fordownstream processes• May have difficulty in consistentlymeeting effluent ammonia limits;• Poorer cold weather performancethan other options;• Must be conservatively designed dueto concerns with shaft failures andtemperature effects on performance• High capital cost.Project No. 30825 – September, 2012 Page 17