Residential and commercial blackwater and greywater recycling systems have entered the Canadian marketplace with continual support from certifying bodies like the National Sanitation Foundation International (NSF Canada), Bureau de Normalisation du Québec (BNQ) and European Union EN12566-3 certification. (See Thomas W. Bain and Allan Hazelton’s “Complete Wastewater Resuse [sic]: The Ultimate Solution for Onsite Wastewater Treatment,” which was published in the June 2016 Ontario Onsite Wastewater Association conference-edition newsletter. Visit www.oowa.org.) These third-party agencies review the technologies with testing and provide certification to global safety standards. NSF International establishes criteria to improve awareness and acceptance of water reuse technologies that reduce impacts on the environment, municipal water and wastewater treatment facilities, and energy costs.
The treated wastewater (i.e. high-quality effluent) from a certified NSF 350 system can be used for restricted indoor water use and/or unrestricted outdoor water use. Such membrane bioreactor systems can be suited for water reuse applications due to the low-foul, durable, flat-sheet membranes that use micro-sized pores for physical separation of solids from the wastewater. These systems typically have a recirculating feature to aid in nitrate removal. This decentralized treatment system offers lower costs than centralized sewering, and is often ideal for single homes or small communities. Proprietary products with low maintenance needs can be especially ideal for the residential market, but other membrane bioreactor systems have mandatory chemical ‘clean-in-place’ (CIP) control for cleaning every two weeks.
Capturing and treating the indoor greywater to be reused for outdoor applications can halve water usage, decreasing the freshwater demand of the home or facility. Close to half of the homes in Nova Scotia are already on septic systems, equating to more than 1 million L (264,175 gal) of wastewater generated per day and dispersed below the ground surface.
Of course, homes are not the major consumers of local water sources—commercial and major manufacturing facilities have far bigger impacts. For instance, in Prineville, Oregon, Apple Inc. used 102,000 m3 (133,400 cy) of water last year to run its facilities and evaporative cooling systems in its data centres. (See Sara Jerome’s article, “Apple Enters the Wastewater Business” in Water Online.) Due to the high volume of water consumption, many large corporation campuses and high-rise buildings look to developed their own wastewater treatment facilities and reroute the piping to reuse water.
General guidelines for water quality standards
While the U.S. Environmental Protection Agency (EPA) has published guidelines for reuse of wastewater, these are only recommendations and are not typically enforceable. It requires similar recommended permit limits set by the World Health Organization (WHO). WHO also addresses microbiological water quality of <1 fecal coliform for the last seven days, with no single sample to exceed 14 fecal coliform CFU /100 ml. Additionally, it requires an additional contact tank for a ≥ 1 mg/L 30-minute chlorine residual for adequate disinfection.
Canada has developed similar guidelines for household-reclaimed water for toilet and urinal flushing. These require turbidity to be ≤ 2 NTU median and ≤ 5 NTU maximum, as an alternative to monitoring total suspended soils (TSS). Additionally, a free chlorine residual of ≥ 0.5 mg/L is required at the point where the treated effluent leaves the reservoir or storage.
To compare the permit limits for reuse, Figure 1 illustrates side-by-side requirements for outside surface irrigation. It shows how water quality of reused treated water inside of the home or building is under stricter treatment requirements and regulations. Some Canadian provinces have also adopted water reuse water quality criteria, including Alberta, Manitoba, Prince Edward Island, and Saskatchewan.
| RANGE OF BENEFITS |
| The benefits of reusing treated water to reduce freshwater demand for the onsite irrigation of green spaces, landscaping, and lawns are numerous.Recharge groundwater Greywater recycling for irrigation replenishes ground water, helping the natural hydrologic cycle to keep functioning.Reduce strain on septic system or treatment plant Greywater makes up the majority of the household wastewater stream, so diverting it from the septic system extends the life and capacity of the system. Develop otherwise unsuitable real estate Maintain soil fertility Support plant growth |
