Biological treatment is a flexible solution for removing pollutants and other contaminants from wastewater.
Biological treatment systems can remove multiple pollutants in a single treatment step including organic contaminants and nutrients such as nitrogen or phosphorous. Generally, this makes it a more cost-effective solution than chemical or physical treatment. This also makes biological treatment ideal for large scale facilities in the municipal and industrial sectors.
WEC Projects can engineer systems across the spectrum of requirements from large treatment facilities for municipal and industrial applications to smaller systems addressing individual needs.
While biological treatment alone can be utilised in applications where the standards for the effluent are lower, WEC Projects can also develop systems that combine biological treatment with chemical and/or physical treatment (filtration, solid/liquid separation, membrane technology etc) to meet specific effluent quality standards or for water reuse.
Resource recovery and re-use has become a critical issue for many water users looking to improve their overall environmental impact. Biological treatment can address this need, allowing users to re-use water for industrial processes, irrigation or to return to source and to potentially generate biogas which can be used for power generation or heating applications. Moreover, sludge can be beneficiated for use as an agricultural fertiliser. Biological treatment thus fits well into the circular economy where the emphasis is on waste elimination through re-use and recycling.
Aerobic and Anaerobic Digestion
Biological wastewater treatment essentially utilises the natural processes of microorganisms (biomass) to breakdown nutrients and organic compounds. The process can take place either aerobically, i.e. in the presence of oxygen, or anaerobically, i.e. without oxygen, depending on the requirements.
Aerobic digestion requires the presence of oxygen in order for the biomass to operate effectively. As a result, air is circulated through the treatment tank. The system is capable of removing both nutrient and organic pollutants, making it suitable for applications such as domestic water treatment. The retention time in an aerobic reactor is short due to the high growth rate of the biomass, allowing for larger amounts of wastewater to be treated. The by-products of such a treatment method include nitrogen compounds and phosphates which can be used for agricultural fertilisers.
Anaerobic digestion utilises a biomass without the need for oxygen. This process differs from the aerobic process in that it cannot remove nutrients from the wastewater, thus it is used more commonly as a primary treatment to treat industrial wastewater. In municipal applications anaerobic digestion is commonly used for sludge stabilization. A particularly valuable by-product of the anaerobic digestion process is biogas, which contains methane. Biogas can be used in applications such as power generation and heating. The biogas produced by the anaerobic process can be used to power the treatment plant itself, drastically reducing its operating costs.
Anaerobic digestion is a sensitive process requiring a delicate balance in temperature and pH level. The process also has a higher retention rate in the digester, which results in the need for larger digesters to treat similar amounts of waste compared to aerobic digestion. However, it can also cope with waste that has a higher organic solids content.
Technology to Maximise Water and Resource Recovery
Among the biological treatment technologies available to WEC Projects is Nereda®, an advanced treatment process which utilises a unique aerobic granular biomass capable of simultaneously removing nitrogen and phosphorous to produce a high-quality effluent. Additionally, Nereda® has a much smaller physical footprint and saves 50% in energy consumption.
WEC Projects also has the exclusive African rights to Struvex® technology, a patented process for recovering nitrogen and phosphorous from sewage sludge in the form of magnesium ammonium phosphate (MAP). It can be deployed either upstream or downstream of digestion. MAP has a number of uses including as a slow-release fertiliser.
WEC Projects’s partnership with Modern Water enables it to offer the proprietary all membrane brine concentrator (AMBC) technology for recovering high quantities of water from highly saline wastewater streams or brine concentrate streams from reverse osmosis plants for water reuse applications. The process can achieve brine salt concentrations as high as 200 000 mg/l , producing clean, reusable water and a concentrated brine feedstock from which resources can also potentially be recovered.
NewGeneratorTM is a compact, portable and modular sewage treatment solution incorporating an anaerobic digestor. 99% of the water can be recycled for water reuse applications, such as flushing of toilets, reducing consumers’ reliance on local water supply. The treatment by-products include a nutrient rich solid waste ideal for agricultural uses, and biogas which can be for domestic heating and cooking. The system can be powered by grid electricity, solar or generator.
From Consultation to Turnkey Projects
WEC Projects offers turnkey packaged or custom engineered solutions for both aerobic and anaerobic wastewater treatment.
For anaerobic solutions the company can offer a number of process options such as Continuously Stirred Tank Reactors (CSTR), Expanded Granular Sludge Bed Reactors (EGSB), and Upflow Anaerobic Sludge Blanket (USAB) systems. Aerobic solutions include conventional activated sludge, trickle filter, membrane bioreactor and mixed bed bioreactor process configurations.
In addition to singular biological solutions, WEC Projects offers multiphase systems incorporating pre-treatment, filtration, biological treatment and chemical treatment as well as sludge beneficiation and biogas recovery to suit specific requirements and effluent standards. The company can develop solutions to meet any requirements from large scale municipal and industrial facilities to smaller systems ideal for use in small and remote communities, tourist facilities, schools and small businesses.
For the latter, WEC Projects can offer the locally manufactured NewGeneratorTM, a unique and highly flexible packaged sanitation system ideal for smaller applications.
The company’s laboratory services can provide biological testing and, through WECAssist, offer ongoing operational support and service level agreements where necessary.
Through its partnership with WEConsult, the company can provide full consulting services to clients to assist them in developing the most efficient and cost-effective solutions, including feasibility studies; capex and opex analyses; practical and cost analyses for resource recovery and recycling, e.g. biogas (for energy, heating etc), sludge (for fertiliser), and water (for irrigation, industrial processes or even human consumption) and more to meet the growing need for environmental compatibility.
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