Water Treatment: Tick, tock for tech solutions
It is that time of year, when we reflect on what has happened, and what might happen.
Sometimes that can be interesting. Yet the water and wastewater industry tends to deal with incremental and slow change. After all, the basic principles of water treatment have not changed much since the Romans refined the aqueducts into engineering marvels nearly 2,500 years ago. Back then, the solution to pollution was dilution, achieved with small populations and lots of water constantly flushing through the bathhouses.
Today, we still have some Roman aqueducts in operation, albeit the infrastructure has largely been reconstructed over the centuries. It’s hard to imagine how much it would cost in today’s dollars to construct something for centuries of use, as it used to — especially given even the best equipment today only has 60- to 100-year lifespans.
Today, the biggest issues are climate change, water scarcity and carbon credits. Part of this is due to the concentration of populations in urban areas and our desire to shape the landscape to our permanent residency. As a result, the water and wastewater industry has found ways to enhance the natural hydraulic cycle and introduce the human hydraulic cycle so that the 1.8 billion people anticipated to be living in areas of water scarcity by 2025 might continue to have safe and reliable sources of drinking water and sanitation. Industry has developed fine filtration, ultra-filtration, nano-filtration and ever finer to continually improve ways to enhance water treatment and make out water safer. It also continues to find ways to reduce water use, through conservation, maintenance and low-use fixtures.
At the end of the day, the water and wastewater industry is still dealing with the solution to pollution. When operators use a filtration system among the treatment processes, such reverse osmosis, it can obtain a high quality of water. However, they still have high levels of reject water with concentrated contaminants due to solubility limits. This is either further treated or disposed. A simple example would be a desalination plant with an intake for raw sea water, and then an effluent pipeline for reject water, which can have four times the salinity and requires dilution to reduce the toxicity and separation from the intake to avoid cross contamination.
However, if plant operators take our onceused water resources and bring them back through water treatment systems, they can mitigate the impact of first-use systems and obtain a valuable new source water with a reduced reject flow, and subsequent disposal impacts. We have a number of systems employing various technologies to achieve high-quality water for reuse in industrial processes. Yet at the end of the day, we are not at a closed-loop water system. NASA has somewhat of a closed loop system, and recycles much of the water for reuse on the space station.
Through adsorption processes — for organic molecule removal, filtration for contaminate and salt removal, and bacteriological treatment and disinfection — they are able to substantially reduce the amount of fresh water required to be delivered to the space station to meet the basic two litres per day per astronaut required. The end result is a stable concentrated brine solution and potable water. It’s unclear if the brine is disposed in space, or returned and burned upon reentry, but it is surely disposed of at far greater cost than we can afford here.
Canada’s water and wastewater systems may not be able to achieve similar water demands, as they still rely on flush toilets and hot showers. Most cannot readily afford the technologies utilized by NASA. However, operators can take incremental steps to achieve reductions in water demand, improvements in treatment to enable reuse of the water and recycling back to nature for eventual reuse. Infrastructure redevelopment is being implemented through a number of federal and provincial grant funding programs. Some projects are public-private partnerships.
The demand for funding outstrips the available funding, so innovation is often used to attract the funding, and for those smaller systems not subject to government trough funding, innovation is key to minimizing the costs to the users. A number of innovations being considered on new projects are slowly entering practical use and are being considered as effective measures. For example, energy costs for treatment are often a key consideration in the selection of equipment. Through reductions and innovative pressure reduction, there can be operating cost savings. There can be reductions at the source through effective monitoring of the treatment processes such as aeration.
When the dissolved oxygen levels can be maintained by slower running or smaller aeration blowers there are capital and operation benefits. Utilizing micro-generators in pipe flow systems as a pressure reducing valve can result in generating power for feeding back into the electrical grid, or consumption at the point generated. Other means of energy savings can be through heat-recovery systems. Sewer systems are being considered for the available heat energy of incoming water, through heat exchange systems for heating in winter, and conversely, the water can be used as a heat sink for cooling the building in summer.
Meanwhile, the use of membrane treatment for water and wastewater continues to gain favour as a cost effective and space saving means of treatment. Incremental improvements in the monitoring processes for better understanding of the flux rate variations to temperature and specific gravity of the process water are enhancing the treatability and reliability of systems. This is aiding in operating costs, and longer term life cycle savings.
These are just some examples of ongoing innovations and incremental improvements in the water treatment industry. Moving forward, operators need to find a way to make new technologies such as NASA’s cost effective and able to be implemented on a larger scale, and find ways to utilize the residuals to get to the full reuse stage.
Mike Seymour has more than 25 years’ experience in water and wastewater treatment for small decentralized systems throughout B.C. He is currently involved with the BC Water and Waste Association. Seymour is also the principal with MSR Solutions Inc. in Victoria. He can be reached at 250.479.5164.