Wastewater Treatment Innovations
Thinking of Wastewater as a Resource
Innovations in the area of wastewater treatment focus on the premise that wastewater can be a resource. Though innovations in countries such as Sweden often use new technologies and ideas, their underlying philosophy revolves around one of simple common sense. Reuse of waste results in the production of less waste overall and thus saves the environment from further need for resource extraction. It's a good premise, and one that the CRD is exploring when making decisions about wastewater treatment.
The most intensive resource recovery projects to date have taken place in Europe. The degree to which these technologies can be implemented in British Columbia will depend on a number of factors, including operating costs, potential revenues, the value of the resources and public acceptance levels for wastewater resources and the engineering needed to create them.
What do innovations in treatment accomplish?
Innovations can be described by the difference they make to communities. Wastewater treatment innovations satisfy a number of different criteria:
- to integrate planning with other local services, such as solid waste, organics composting programs, energy and public services so that a community benefits from wastewater treatment in a variety of ways
- to lower the costs of wastewater treatment through waste recovery and reuse
- to minimize environmental pollution
- to embrace flexibility, so that new innovations and technologies can be employed as they become available
Treatment Design Innovations
Decentralized Treatment Plants
Decentralized wastewater treatment was used in the past most commonly to serve sparsely populated communities that were too far from larger areas to have sewers extended to them. As cities grew and overtook these communities, they were brought into centralized systems for reasons of health and cost. Recently, however, decentralized treatment has seen a resurgence. Sewer pipeline construction can be costly in established neighbourhoods and membrane-based technology has dropped in cost and become more available, allowing for smaller, more locally based treatment plants.
Satellite Water Reclamation Plants
Satellite reclamation plants remove flows from nearby sewers to produce reclaimed water closer to the use area. This approach can reduce the need for infrastructure such as pumps and pipes, which are often required to return reclaimed water from a central plant. These plants, if feasible, have a number of advantages:
- a smaller footprint, which allows them to blend into existing communities
- excellent odour-removing abilities
- an ability to produce a valuable industrial, non-potable water supply close by that can ease the strain on local water supplies
Membrane Separation Technology
Membrane separation technology involves the separation of liquids from solids, using a variety of methods. A wastewater stream is passed through a series of membranes where impurities are removed. Three common separation systems include ultrafiltration, microfiltration and reverse osmosis. Wastewater treated using membrane technology can actually be rendered so clean that it is potable, though most applications of reclaimed water are for grey water and irrigation use.
Resource Recovery Innovations Around the World
Biodiesel from Fats, Oils & Grease in Wastewater
Biodiesel is made from oil. Biomass to biodiesel conversion technology is developing rapidly in Canada. Fats, oil, and grease (FOG) from wastewater is collected during treatment in plants such as those in Europe and converted to biodiesel through esterification and hydrogenation.
Electricity & Heat from Co-generation
Biogas fueled cogeneration systems can allow a wastewater facility to utilize energy from the treatment process itself. Cogeneration systems produce electricity and hot water from biogas, a naturally occurring byproduct of sludge dewatering. The electricity produced can be used to supply power to anaerobic digesters in the plant, thereby offsetting electricity purchases from the power grid.
Electricity from Biogas or Sewage Powered Fuel Cells
Methane from sludge dewatering plants can be converted into biogas, but it can also be converted into hydrogen, which can be used in direct fuel cells. This provides an option other than the traditional internal-combustion engine for the powering of wastewater plants. Some of these fuel cells are already in operation in various locations in the United States and Europe.
Water-Source Heat Pumps
Water-source heat pumps are being used in Japan to extract residual heat energy from wastewater, after treatment and before discharge by outfall. Similar heat extraction technology is now developing for extracting heat from wastewater in sewer pipelines. Wastewater temperatures average around 16 degrees Celsius. This heat can be used as an energy resource.
Reclaimed Water from Wastewater
Reclaimed water from wastewater is a technology which is being implemented in wastewater treatment plants around the world. Using membrane technology, water can be purified and used in grey water applications, in irrigation or as a supplement to existing ground and surface water sources during times of low flow.
Biogas from Wastewater & Sludge
Biogas is produced from methane, which is a biproduct of biosolids processing. Methane escapes from sludge as it is digested by microorganisms during the dewatering process in a solid waste facility. Anaerobic digestion has also been shown to degrade persistent organic pollutants such as dioxins and chlorobenzenes.
Biogas, in many countries in Europe, is already being used to fuel cars, taxis, trucks and public transportation. As a fuel source it can be refined as a cooking fuel, for use in homes and restaurants; biogas can also be burned in plants along with wood or other waste in order to power factories.