Sustainable Sewer

311944656_fa407a23c3_m Many parts of the world have no modern sewer system. In China, it is reported that about 41 trillion kilograms of untreated sewer is pumped into lakes and rivers every year. In Mumbia, one report states that there is an area where one toilet serves 5,440 people, (source: Blue Covenant, Maude Barlow, 2007). In North America we are blessed with sanitation, and considering that there is estimated to be almost one toilet in the US for every one of the more than 303,000,000 people, I think we have very little to complain about. North Americans waste billions of litres of water of water everyday, and a lot of this goes into the sewer system – that is not a sustainable situation. Locally, the Regional District of Kootenay Boundary (RDKB) is in the process of wrapping up Stage 1 of their Liquid Waste Management Plan (LWMP). This stage of the process is designed to gather background material and preliminary concepts for the future requirements based on population and legislative requirements. The next stages plan out the details of a proposed system and identify costs and action items required.¬† Read more after the jump…

Decentralized Systems

I’ve been part of the technical review committee on the LWMP, and appreciate the effort that has gone into the process so far. It’s just surprising that very little vision casting is required under this process, instead, stock standard off the shelf options are identified as sensible options, with minimal innovation. The very nature of having sewer as a regional function is contentious, as areas such as Warfield, Rossland and parts of Trail require large pump stations to get the sewer from these towns to the regional sewer treatment plant – along the banks of the Columbia River. The benefit of collecting sewer from all over, and treating it in one place is in the centralization of the service, and the localization of the associated risks. But in today’s enlightened engineering world, bigger is not always better, centralization is not always the greatest answer. A related example is the recent popularity of rainwater collection for toilet flushing and outdoor irrigation. Until a couple of years ago, society seemed to feel that water from the sky was somehow inferior to that from their municipal water service, now people are viewing it as an alternate supply stream to be tapped rather than disposed.

1434741850_faf489ac7e_m Something similar has happened in sewerage systems around the world. We went from no, or minimal treatment, to onsite treatment, to large scale municipal treatment, and I think the curve is returning back to smaller scale, lower energy solutions where possible. For example, many greenfield sites in Australia were on the outskirts of serviced areas, and had the option of connecting to the municipal system at a high cost of capital construction, or instead,¬† developing a small scale alternative. Systems such as the Biolytix, which I’ve written about before, present¬† an option that is lower cost for many developing communities, and even in retrofit examples. However the market and design codes are tied up in traditional methods and philosophies. (I use this word, but don’t believe for one second that sewer technology developed over the past 150 years represents traditional methods!) Considering that the region is considering spending some 40-50 million dollars (in today’s terms) for an upgraded plant, surely the option to decentralize at least some of this treatment should be examined, and not just as a satellite plant for Rossland.

Diverting the Waste Stream


Another serious consideration is finding ways to reduce the generation of sewerage, i.e. diverting the waste stream into useful water. Examples are low flush or high efficiency toilets, (or even composting toilets and waterless urinals), low flow showerheads, greywater recycling, cross connection identification, and minimizing infiltration issues. If through behaviour and technological improvements to a water system, a municipality is able to reduce consumption by over 30%, it must be possible to find 10-20% reductions in the household consumption that ends up in the sewer anyway. These measures are not being investigated aggressively enough considering the cost of delivery of water and the removal and treatment of sewerage.

Long-term Sustainability and Environmental Leadership

The LWMP process is a useful one, but the big picture of long term sustainability needs to be addressed at all stages of the process. This sustainability needs to reflect energy demands of the system, long term operating and maintenance costs, and reductions in the per capita sewer that should be generated if people started to use water more wisely. Servicing the needs of a growing population is always tough, particularly when expectations of what that service looks like, (or in the case of sewer, does look like, i.e. remains invisible to most people), remain the same. Leadership in these issues is needed. Raising the bar on expectations is a good thing, whether a centralized system is the preferred option, or innovative small scale systems are proposed, true leadership involves making far reaching decisions with the available information and technology.

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