Wastewater Isn’t Useless Water: Improving residential water consumption onsite

by Katie Daniel | March 7, 2017 10:14 am

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By Jennifer Cisneros
By 2027, the world’s population is predicted to double, meaning millions more people will be denied access to clean water. Scientists from around the world are urging an immediate adoption of clean waste-processing technologies, along with the development of infrastructures to protect water resources and areas with delicately balanced ecosystems. Even in countries like Canada, having access to clean, fresh water is too precious to take for granted.

While onsite wastewater treatment systems (e.g. septic systems) are nothing new, the idea of recycling water generated on properties is becoming very popular. Onsite septic systems are called by many different industry terms, including:

• advanced, wastewater treatment systems;
• scalable, distributed sewer systems;
• residential blackwater/greywater treatment systems; and
• decentralized water/wastewater management systems, etc.

Regardless of the terminology, they can help resolve the many issues concerning infrastructure alternatives, budget constraints, and site planning. Most national and international environmental protection agencies’ policy literature identifies finding a viable distributed approach to achieving a water management solution as an issue of economic, legislative, and institutional importance.

Water recycling is a key component of sustainable water engineering. However, water and wastewater treatment are two separate and broad fields, involving a number of technical disciplines for best practices. Water treatment standards are mainly guidelines involving finer filtration (e.g. reverse osmosis [RO]) or disinfection (e.g. chlorine or ultraviolet [UV]); they are rarely included in water recycling or reuse schemes involving wastewater treatment, have any legal basis, or are subject to enforcement.

Significant potential with the urban core
While municipal treatment plants tend to be perceived to be the best option available, there are many other methods communities can adopt. The layout, engineering, and integrated design allows smaller systems to treat wastewater and stormwater at its source, while reducing the need for large piping, site disruption, or enormous amounts of energy to pump untreated or partially treated water through kilometres of a sewer network, never to be sent the water back to its original source.

Additionally, utilities are beginning to recognize the benefits of these technologies for overloaded plants. While not yet common practice, they have been installed on commercial properties to pretreat the wastewater, screen it, and remove most of the organics prior to the municipal treatment plant. These systems can address compliance issues for small communities and/or remote areas, and can be designed for varying levels of wastewater treatment, depending on the discharge location and requirements.

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Residential onsite water-recycling can have significant potential benefits beyond utility bills for homeowners. For example, compared to conventional water-efficient homes built using low-flow fixtures, residences with water recycling systems could use almost half as much water (due to treated greywater being circulated to the toilets), while generating only one-sixth the peak sewage.

For municipal systems, the decrease in loading caused by pretreatment with onsite systems on commercial properties may mean more effective treatment for undersized wastewater treatment plants. Water reuse enables municipalities to decrease displacement and discharge into surface waters, decreasing demand on the local potable watershed. This could lead to lower fees for water rights and sewer tie-in fees for builders, while significantly stretching allocations for reduced water.

Ecological water management systems and both decentralized residential and commercial wastewater (i.e. blackwater/greywater) treatment technologies can satisfy project goals and provide more options for using treated water. With a long, proven history, these systems perform exceptionally well in achieving the new higher levels of nitrogen removal, net-zero water goals, and optimal effluent quality with automated, energy efficiency.

What are the specific challenges of water recycling?
Some companies are actively involved in the stewardship of the wastewater and sewage treatment industry, working with provincial and national regulatory health authorities to advance technologies safeguarding public health and protect fresh water resources.

The largest potential source of onsite water in homes is greywater drained from showers, laundry rooms, and sinks. Typically, two-thirds of indoor water is greywater, with the remaining one-third blackwater from the toilet. It is believed “adoption of off-the-shelf residential technologies could reduce indoor water use from approximately 200 L per day to 89 L [53 to 24 gal] per day.” (For more, see Elizabeth Hendriks and Sarah Wolfe’s article in ForesterDailyNews online here[3],  retrieved 07/21/2016.) Some septic homeowners’ guides suggest the typical single-family home indoor water use average can be about 1000 L (264 gal) daily, with leaky toilets wasting as much as 900 L (238 gal). (This comes from Waste Water Nova Scotia Society [WWNS] and Nova Scotia Environment’s [NSE’s] A Homeowner’s Guide to Septic Systems, published in November 2009. For more, click here.[4]) Greywater composes 50 to 80 per cent of residential wastewater generated from all of a household’s sanitation uses.  (For more, see Alberta WaterSmart’s 2011 “Greywater Recycling and Reuse in Alberta Report,” which was posted online at www.albertawatersmart.com[5].)

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Wastewater treatment is a complex process that demands a combination of solutions, rather than a one-size-fits-all approach. All septic systems require oxygen so bacteria can properly convert complex molecules into basic ones like carbon dioxide (CO₂), water (H₂O), and nitrogen, as well as eliminate viruses like e.Coli. Therefore, the major difference between the tertiary systems is how the oxygen gets to the bacteria. Some pump air into the sewage, while others put the sewage into an area with oxygen.

All daily flow calculations start with the number of bedrooms, but this is not the case when it comes to other factors. Average daily use per person is approximately 275 L (72 gal); therefore, the maximum daily flow could be around 500 to 600 L (132 to 158 gal) per bedroom. For example in Ontario, the following Ontario Building Code (OBC) ‘bedroom rate’ guideline, provided by the Ontario Onsite Wastewater Association (OOWA), assumes for every bedroom there are two people living in a residence. For example:

• one bedroom: 750 L (200 gal);
• two bedrooms: 1100 L (317 gal);
• three bedrooms: 1600 L (422 gal);
• four bedrooms: 2000 L (528 gal); and
• five bedrooms: 2500 L (660 gal).

A professional should always be consulted for site parameters and other factors to take into consideration. In Ontario, all septic systems within a single lot and rated to accept a total daily flow rate of <10,000 L (2640 gal) must comply with OBC, while other local or provincial regulations for sizing onsite systems are in play elsewhere. Other factors to consider for water usage will be the terrain/soil site conditions, along with the fixtures used—that is, the types (low-flow, high-efficiency, or not) and number of washers (dish/laundry), faucets, showers, tubs, and floor drains used or installed on the premises.

Ever-evolving system options
For most advanced treatment systems, whether they are integrated fixed-film activated sludge treatment, trickling filter systems, extended aeration systems, or onsite membrane bioreactors (MBR), the technology easily scales up to accommodate the flows between small-scale packaged systems (as low as 1-m³ [35-cf] daily flows) and full-scale wastewater treatment plants (beyond 600 m³ [21,190 cf]). Since each system has a slightly different setup, depending on the site conditions will affect the level of maintenance willing to be undertaken.

The following are adaptive wastewater technologies that employ highly efficient treatment processes:

• effluent screening (provides pre-treatment)—septic-tank deflection devices designed to screen (down to 3-mm
  [118-mil] solids) insoluble debris from wastewater to promote natural attenuate flow and sedimentation (and has a cleaned-in-place swabbing feature);
• submerged aeration (typical treatment)—fine- or coarse-bubble supplementary aeration that creates a vortex circulation, mixing the liquid in the wastewater to promote removal of biological oxygen demand (BOD);
• extended aeration (typical treatment)—a complete mixed-activated treatment system utilizing submerged aerators for suspended-aeration wastewater treatment process;
• trickling filter (enhanced treatment)—automated, recirculating, pre-engineered, advanced wastewater treatment system employing a spray function to saturate textile-media;
• fixed-film technology (integrated, enhanced treatment)—submerged, oxygenated, attached growth media system
  to create robust growth with naturally occurring bacteria and a nitrified/denitrified recirculation action to treat wastewater; and
• membrane bioreactors (ultrafiltration)—in this strategy membranes and aeration process act as an impenetrable physical barrier to produce water filtrate that is
  99.9 per cent removed of pollutants.

ALTERNATIVE REGULATORY PATHWAYS

For more information on alternative regulatory pathways to innovation, see: the province of British Columbia’s 2015 “Onsite Sewage Systems” at www2.gov.bc.ca/gov/content/environment/waste-management/sewage/onsite-sewage-systems; Union of British Columbia Municipalities’ 2008 “Sewerage System Memorandum of Understanding (MOU)” online at www.ubcm.ca/assets/Resolutions~and~Policy/Policy~Papers/2008/PolicyPaper5SSRMOU.pdf; Ontario’s 2015 “Showcasing Water Innovation Final Report: Communities Adopting Innovative and Sustainable Water Management;” “Alternative Solutions: Case Studies from: Mississauga, Burlington, Kitchener,” which was presented at the 2011 Ontario Building Officials Association Conference; and Ontario Ministry of Municipal Affairs and Housing (MAH) Building Materials and Evaluation Commission website found at www.mah.gov.on.ca.

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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[8].) 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[9].) 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 A greywater recycling system can enable the development of land unsuitable for a properly sized septic system. Maintain soil fertility The nutrients in the greywater are broken down by bacteria in the soil and made available to plants. This helps maintain soil fertility. Support plant growth Greywater can support plant growth in areas that might not otherwise have enough water.

Conclusion
It is imperative wastewater be treated before discharging to surface waters, and discharge should be minimized to protect the surrounding ecosystems. Wastewater management has historically shifted toward a centralized scheme, with the public perception being a centralized sewer best protects the public and environmental health. However, water tables are dropping at drastic rates, and sewers continue to discharge trillions of litres of untreated sewage into surface waters worldwide every year.

The environmental and health effects of this political negligence are unacceptable. Engineers and regulators in the wastewater industry need to protect both public and environmental health in the most effective and sustainable manner. For this to happen, many in the water sector need to consider alternative approaches that could be implemented in both new development and infrastructure upgrade projects. Water reuse and soil-based wastewater treatment systems are only two of the many options available to provide communities with flexible and sustainable solutions.

All options need to be evaluated, especially when considering systems that provide greater protection of public and environmental health. Future developments in policy will include guidance on treatment strategies, cross-connection protections, and better management of an important resource.

RANGE OF BENEFITS

Possible Water Efficiency (WE), Sustainable Sites (SS), and Innovation points can be achieved with water reuse systems for projects seeking certification under Canada Green Building Council’s (CaGBC’s) Leadership in Energy and Environmental Design (LEED) rating programs. For example, for projects certifying at the building scale using LEED Homes Mid-rise v3, the following credits can be earned for building wastewater recycling and reuse: SS credit 2, Landscaping (this is the WE: Outdoor Water Use under LEED v4); WE credit 1, Water Reuse (this is WE: Total Water Use under LEED v4); and Innovation in Design (ID) credit. For projects certifying at the district scale using LEED Neighborhood Development v3 or v4, credits that can be earned include: Green Infrastructure & Buildings (GIB) credit 4, Water-efficient Landscaping; GIB credit 14, Wastewater Management; and ID credit. For projects using LEED Commercial Interiors Mid-rise v1, there is SS: Innovative Wastewater Technologies, while Beyond LEED Homes Mid-rise v3 offers Energy & Atmosphere (EA) credit 1, Testing & Verification.

[10]Jennifer Cisneros is the director of marketing at Bio-Microbics, and also chairs the Marketing Committee for the National Onsite Wastewater Recycling Association (NOWRA). She has worked for the past eight years with the Technical Practices and Education Committees at NOWRA, along with various departments at Bio-Microbics, to create, write, and distribute content for the water industry. She can be reached at jcisneros@biomicrobics.com.

Source URL: https://www.constructioncanada.net/wastewater-isnt-useless-water-improving-residential-water-consumption-onsite/

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