By Dragan Rokic, P. Eng., WorleyParsons Komex
Wastewater and Sewage Treatment on Site at Dockside GreenEngineering
At Dockside Green, a wastewater collection, treatment and disposal system has been constructed to minimize the environmental impacts of effluent discharge to the environment. It creates a closed loop ...
At Dockside Green, a wastewater collection, treatment and disposal system has been constructed to minimize the environmental impacts of effluent discharge to the environment. It creates a closed loop cycle where the treatment of wastewater on-site reduces operating costs and provides reclaimed water for toilet flushing, landscape irrigation and a water feature. The reclaimed effluent will meet the Municipal Sewage Regulation (MSR) criteria for unrestricted public access.
The wastewater system includes sewage collection mains, tertiary-level treatment facilities and provisions for reuse of reclaimed wastewater (see diagram p. 25). It also provides for a discharge of surplus reclaimed wastewater, and off-site disposal of screenings and dewatered sludge.
Technologies combine preliminary treatment (fine screening) with flow equalization and biological treatment based on a suspended-growth, activated sludge process. This is coupled with in-tankage membrane solids and liquid separation. Hollow fibre ultra-filtration membranes with a nominal pore size of 0.04 m are used for this purpose.
Permeate from the membrane bioreactor tank is transferred to UV disinfection post-treatment and finally to an effluent storage tank prior to reuse. Residual chlorination is employed to a portion of the effluent volume which is recycled to buildings for toilet flushing and green roof irrigation.
The wastewater treatment system will treat all domestic sewage flows generated on site. Two similar parallel customized process trains each rated for 190 m3/day will be installed, one in phase I and the second in phase 2. Each of these trains can handle continuously 50% of the total design flow, and temporarily 100% of the total design flow, at full build-out. The total ultimate wastewater system treatment capacity will be 380 m3/day.
With two identical trains constructed in parallel, one can function satisfactorily while allowing for periodic maintenance of the other. All process and mechanical system components have full redundancy so that all effluent quality requirements can be maintained during routine maintenance work.
The up-front equalization tank will provide flow equalization and attenuation of diurnal fluctuations and hydraulic surges to the plant. This tank has an emergency bypass/overflow to the city of Victoria municipal sewer system.
A high pressure pumping system will supply reclaimed water for toilet flushing, rooftops and balcony planter irrigation in all buildings. Sodium hypochlorite is added to this water to maintain a residual disinfectant. Organic blue dye is also added to distinguish the water as reclaimed and to mask a yellow tinge that may occasionally be apparent in the permeate.
A low pressure pumping system distributes reclaimed water to the central waterway to augment rainwater flows and to nourish the flora and fauna in the greenway through a drip-irrigation system. This water is not chlorinated, but it is pre-disinfected with ultra-violet light. The pumping system can also be used to recycle water from the lower pond at the north end of the site to the upper pond near the south end to enhance “polishing” of the water in the waterway.
Finally, surplus reclaimed water and rainwater are discharged from the waterway to the Victoria Harbour via a shoreline dispersal outlet.
Dockside Green Developers: Windmill West, Vancity
Architects: Busby Perkins + Will architects (phase 1), Dysarchitecture (phase 2)
Consultants: WorleyParsons Komex (civil), Stantec Consulting (mechanical, electrical, LEED coordinator), C. N. Ryzuk & Associates (geotechnical), SNC-Lavalin Morrow Environmental (environmental), Read Jones Christofferson (structural), Focus (surveyor), PWL Partnership (landscape)
Contractor: Farmer Construction