Until October 30, 2015, The City of White Rock’s water utility was privately owned and operated. The water supply for the city that comes from the Sunnyside Aquifer has naturally occurring arsenic and manganese. Although the maximum acceptable concentration (MAC) of these elements were within Health Canada’s guidelines, the City took immediate steps to improve water quality. One of these steps was studying which water treatment techniques could reduce these elements in the drinking water.
The City collaborated with RES’EAU-WaterNET, to develop a mobile water treatment pilot plant to conduct testing of various combinations of technologies and identify a sustainable and robust water treatment system capable of removing naturally occurring arsenic and manganese from the groundwater sources. The mobile facilities allowed for faster, accurate, and more cost-effective assessment of potential technologies than traditional methods.
The City submitted grant applications towards the construction of a water treatment plant for arsenic and manganese treatment, under Canada’s and the Province’s Clean Water and Wastewater Fund (CWWF). In March 2017, the City of White Rock received $11.79 million in grant funding from the Government of Canada and Government of British Columbia. The funding went towards the City’s $14.2 million arsenic and manganese water treatment plant to address the City’s water quality and ensure a healthier community.
Arsenic is a natural element that is present in the earth’s crust. It is often found naturally in groundwater, through erosion and weathering of soils, minerals, and ores. Higher arsenic concentrations are usually present in ground water, and could pause a serious threat to human health. Arsenic is one of the many chemicals for which Health Canada has set guidelines. The guideline has been established at 0.010 mg/L (10 µg/L). The guideline is based on lifetime exposure to arsenic from drinking water and takes into consideration the ability to measure arsenic and to remove it from drinking water supplies (Health Canada, 2006).
The Guidelines for Canadian Drinking Water Quality includes an aesthetic objective for manganese in drinking water with a value of 0.05 mg/L (50 µg/L). At higher concentrations, manganese could have an impact in causing stains on laundry and leaves deposits on supply pipes in the distribution system and in residential plumbing that may give water a metallic taste. The presence of manganese in water may lead to the accumulation of microbial growths in the distribution system. Even at concentrations below 0.05 mg/L, manganese may form coatings on water distribution pipes that may slough off as black precipitate. In May 2019, Health Canada established a new guideline for manganese. An MAC of 0.12 mg/L for total manganese in drinking water, and an aesthetic objective (AO) of 0.02 mg/L (20 µg/L) for total manganese in drinking water.
The White Rock Water Treatment Plant is designed to treat the City’s existing groundwater supplies to remove naturally occurring manganese and arsenic. The drinking water sources are the Sunnyside Uplands Aquifer and 7 wells located throughout the City. The utility serves a population of approximately 20,000 people.
The water treatment plant process is multi-stage and includes the following key treatment components:
- Pre-Oxidation with ozone for arsenic and manganese in the raw water supply;
- Removal of manganese using Greensand Plus media filters;
- Removal of arsenic using Bayoxide E33 media filters;
The treatment objectives of the White Rock Water Treatment Plant are to deliver drinking water meeting the following operational targets:
- Mn < 0.02 mg/L
- As < 0.002 mg/L (95% of the time, 0.005 mg/L for 5% of operation)
All other water quality parameters shall meet the objectives of the Guidelines for Canadian Drinking Water Quality (GCDWQ).
The research conducted by the City of White Rock and Res’eau-WaterNET showed that the use of ozone as a pre-oxidant, followed by greensand and adsorption filter media for the removal of manganese and arsenic, respectively, is effective for groundwater sources like White Rock’s water supply. The design team chose filtration using Greensand Plus media for manganese reduction, and AdEdge E33 adsorption media, for arsenic polishing to achieve the low target levels required by the City.
The system is designed to provide up to 1 mg/l of ozone dose for up to 15 MLD of water to treat. The design of the White Rock Water Treatment Plant includes pre-oxidation with ozone injected via side stream injection; the concentrated ozonated water is injected into the raw water through an in-line mixer to oxidize metals in raw water. On-site generated ozone is used to pre-oxidize the arsenic and manganese in the raw water. The ozone converts the arsenite form As(III) to the arsenate form As(V). It also converts Mn(II) to Mn(IV). Both oxidized forms are more readily removable in downstream filtration and adsorption processes.
Greensand Plus filter media was selected for removing manganese from groundwater supplies. A Greensand Plus manganese dioxide coated surface acts as a catalyst in the oxidation reduction reaction of manganese. The silica sand core of Greensand Plus allows it to withstand waters low in concentrations of silica, TDS, and hardness without breakdown.
AdEdge Water Technologies Bayoxide E33 was selected for Arsenic removal. The E33 media provides significant reduction of total arsenic, including both arsenic (III) and arsenic (V). It is also effective in reducing other heavy metals such as lead, antimony, and others. This ferric oxide-based product has been successfully used in hundreds of installations around the globe.
The Engineering and Operations staff at the City of White Rock worked with the EOCP to pre-classify, and officially classify the plant as a Level III water treatment facility. The facility became fully operational in May 2019. Detailed information on water quality and testing can be found at the City of White Rock’s Water Page – http://whiterockcity.ca/230/Water