Iona Deep Sea Outfall...

Iona Island Wastewater Treatment Plant (WWTP) - History and Influence...

Iona Island WWTP is a primary sewage treatment plant for Vancouver Sewerage Area of the Greater Vancouver Regional District (GVRD). It treats sanitary sewage primarily from City of Vancouver and discharges to Georgia Strait. The plant operates under a plant permit issued by the Ministry of Environment that dictates the conditions of discharge. Under the permit the plant is not to exceed the following criteria :

• Flow - 1,530 ML / d
• BOD - 130 mg / L
• TSS - 100 mg / L

The Vancouver Sewerage Area sewer system is a combined sewer system: the Dry Weather Flow is sanitary sewage; the Wet Weather flow is sanitary and storm flow. Prior to the 1960's, effluent discharged directly to the Fraser River and Burrard Inlet for Vancouver Sewerage Area. GVRD was ordered to construct treatment facilities to treat combined flows and reduce English Bay pollution.

Constructed in Stages Beginning in 1960...

Stage 1: 1960-1963: influent pump station, 5 sediment tanks, 2 digesters, 4 sludge dewatering lagoons, effluent chlorination chamber and discharge to Sturgeon Bank channel Stage 2: 1972-1975: 5 sedimentation tanks added Stage 3: 1978-1979: sludge thickener and 2 additional digesters Stage 4: 1983-1984: 3 sedimentation tanks added Stage 5: 1986-1987: 5 sedimentation tanks and sludge thickener for original 2 digesters Stage 6: 1986-1987: effluent pump station (EPS] and outfall

The plant was constructed in stages beginning in 1960: The plant has an influent pump station, 15 pre-aeration/grit removal and sedimentation tanks, 2 sludge thickeners, 4 digesters, 4 sludge dewatering lagoons, and an effluent pump station and outfall. The plant treatment processes are characterized as: Coarse Screening, Grit Removal, Pre-aeration, Sedimentation, Sludge Thickening, Digestion, & Dewatering, and Effluent disposal.

In 1995, plant treatment characteristics included BOD removal average of approximately 30% and TSS (Total Suspended Solids) removal of approximately 50%, both at the upper limits of primary treatment capabilities. There is an influent BOD problem on occasion. Plant Operations is working with Source Control on identifying source reduction possibilities from system users. In 1996, Operations carried out a process audit aimed at identifying improvements to existing system for reasonable cost.

Plant Characteristics - 1995 Treatment...

Characteristics	Value
BOD removal (avg. daily)	27,520 kg
BOD removal efficiency	39 %
TSS removal (avg. daily)	31,470 kg
TSS removal efficiency	49 %

Iona Deep Sea Outfall...

GVRD was directed in a 1982 Court Order to construct facilities due to primarily to environmental impacts documented in the receiving waters of Sturgeon Bank. A task force recommended the Deep Sea Outfall as the most effective solution to the pollution of the banks area. The outfall was placed in operation in April 1988. It is a double barrel pipe with a 5km land section on jetty and 3km marine section below the water surface of Georgia Strait. The marine end of outfall is 100m below surface. A series of diffusers staggered over last 500m of outfall distribute the plant effluent. The end of outfall is in a "No Fishing" zone to protect the outfall.

Outfall Monitoring Program - Background...

A Waste Management Permit requirement of the outfall construction, a comprehensive environmental monitoring program in the Strait of Georgia adjacent to Sturgeon Bank was put in place. The program focuses on the area potentially affected by the deep sea outfall. The program began in 1986 with 2 years of pre-discharge monitoring. This comprehensive program costs about $150,000 per year. We balance environmental needs and costs (monitoring program) against the collection and treatment system issues and costs.

The first two years of monitoring were large-scale and multi-compartment programs. Since 1988, the program focus narrowed to monitor one or two compartments in any given year on a cyclic program. Monitoring objectives include :

• Evaluate baseline, pre-discharge environmental conditions
• Compare with post-discharge conditions
• Indicate possible short or long-term effects of discharge on Georgia Strait ecosystem

A committee with representatives from the GVRD, Environment Canada, and the BC Ministry of Environment meets annually to evaluate monitoring results & discuss further monitoring needs. The committee provides a forum to review the monitoring program results, and to suggest program adjustments where necessary. Reporting is on an annual basis and is sent to the BC Ministry of Environment Regional Manager as part of permit requirements. Monitoring reports are available for public viewing in the GVRD Library.

Program Framework...

The program is cyclic. Each complete cycle is 5 years, and 1997 marks the end of the second cycle. Monitoring compartments include :

• Effluent: chemical characterization - organics, heavy metals, conventionals
• Water Column:
• chemical analyses - heavy metals and organics
• fecal coliforms (to address human health concerns)
• floatables and slicks in the Strait of Georgia
• Sediment:
• chemical analyses - metals, organics, acid volatile sulphides (AVS) and simultaneously extracted metals (SEM)
• toxicity testing of sediments
• fecal coliform testing of sediments
• Biota:
• health and structure of infaunal community - fish, organisms - diversity
• body burden measurement of metals and organic contaminants
• histopathology

Monitoring Program Sites...

The receiving water conditions are as follows :

• discharge is to the Georgia Strait (not to Sturgeon Bank any more)
• the tides are north-south orientation
• a northern tendency to the movement of water in this area of Georgia Strait
• Fraser River influences include stratification of the water column and sediment input (a source of sediment, fresh/salt mixture).

Sampling sites vary depending on the component of the monitoring program. A north-south sample line covers a distance of 8 kilometres, centred on the diffuser. An east-west sampling line is about 3 kilometres long. To date results show the following trends :

• physico-chemical characteristics of sediments at all stations appeared to be naturally produced values
• no build-up of organic matter apparent in the sediment
• little or no change in sediment heavy metals concentrations since first measured some 2 decades ago
• infaunal community structure appears normal and healthy (last monitored in 1995)

There is no build-up of organic matter, as measured by total organic carbon and total volatile solids in sediment samples at the diffusers sampling station. There have been sediment heavy metal changes in comparison with the earlier monitoring work (done prior to the GVRD's pre-discharge monitoring) conducted by UBC's Grieve and Fletcher. Also, the testing of biota and benthic communities shows healthy communities.

UBC's results show silver in the range of 0.1 to 0.15 mg/kg. This is well below the Canadian draft interim marine sediment quality guidelines (threshold effects level of 0.73 mg/kg).

Drinking water pH management may see a reduction in effluent copper values in time that may have an impact on sediment copper. There is a high background copper level in the Fraser River at this time that may influence the Iona Outfall measurements. Reduction in Lead concentrations in surficial sediments may be attributed to source control management that saw lead removed from gasoline.

Concentrations of Copper in Surficial Sediments...
Historical Comparison from 1974 to 1994

Sampling station number	Location relative to the diffusers	Total copper concentrations in sediments (mg / kg DW)
		1974	1986	1990	1994
42	4 km N	46	-	44	43
30	2 km N	44	44	43	49
31	1 km N	44	41	42	47
33	Diffusers	43	42	41	33
35	1 km S	44	40	42	44
44	4 km S	40	-	-	44

Concentrations of Lead in Surficial Sediments...
Historical Comparison from 1974 to 1994

Sampling station number	Location relative to the diffusers	Total lead concentrations in sediments (mg / kg DW)
		1974	1986	1990	1994
42	4 km N	18	-	17	12
30	2 km N	16	18	16	13
31	1 km N	16	18	15	11
33	Diffusers	15	18	15	9
35	1 km S	14	17	14	11
44	4 km S	16	-	-	12

Plant and Outfall - Future...

Future Program components are to be determined after review of the second monitoring cycle, with input from committee. Review of the monitoring program to date (2 cycles) will take place in 1997 to have next cycle in place for start of 1998. The requirement for a monitoring program is currently specified in the Waste Management Permit for the Iona WWTP. A number of current activities that will influence the program include a process audit of plant processes, source control strategies based on user pay for service such as TLW fees and a BOD/TSS Industrial pricing strategy, system management including the CSO operational plan for Burrard Inlet and the North Arm of the Fraser River. GVRD is identifying local problems and developing local solutions linking environmental health & conditions with operational responsibilities and remedies.

Plant Capabilities...
Plant Characteristics - 1995 Flow

Characteristics	Value
25 % dry weather flow (DWF)	404.7 ML / d
Peak wet weather flow (WWF)	1,322.8 ML / d
Peak WWF / DWF ratio	3.27
Annual treatment flow	196,293 ML
Annual dry weather flow	147,460 ML