Water treatment technologies and innovations have become the focus of many governments and policy institutions due to the increasing global scarcity of the resource, especially in the last decade.
Conventional treatment processes remove the suspended material and disinfect the water prior to pumping to local authorities, the mining industry and other large industrial concerns. Each stage in the purification process is accompanied by changes in the physical and chemical composition of the water. These changes are constantly monitored and corrective action is taken to prevent the water quality from deviating from the prescribed limits.
According to Dr Jo Burgess, mine water treatment and management research manager at the Water Research Commission (WRC), there are two types of water treatment technologies.
Low water technology, according to Burgess, is adapted from standard technologies to suit rural conditions. These technologies are not necessarily “low-tech”, despite what the classification suggests. Low water technologies include:
• Standard and slow sand filtration.
• The up-flow or down-flow of deep-bed filtration.
• Dissolved air floatation (DAF).
• Robust, inexpensive point-of-use solar stills.
• Fog-collection systems.
Burgess identifies the second category as high or innovative technologies. These systems typically include:
• Solar-powered reverse osmosis (RO) and remote control.
• Wave-powered RO for coastal communities.
• A teeter bed system for natural organic matter (NOM) removal.
• Nano-sponges and nanotech for water treatment.
• Small ultra-filtration systems for rural areas.
• Woven fibre membrane filtration systems for rural areas.
Over the past decade, much attention has been devoted to the engineering, science and technological aspects of wastewater treatment in South Africa. More recently, attention has been redirected to assess the performance and compliance status of wastewater treatment facilities, and to identify the challenges and root causes that underpin poor performance – in particular by municipal institutions. When examined, it has been found that the existing systems failed due to poor maintenance, a lack of skilled operators and a lack of capacity, and not due to the technology itself.
A recent study by the WRC in partnership with the South African Local Government Association (SALGA) considered a national representation of municipal wastewater treatment facilities, and assessed these in terms of the appropriateness of their technology choices in relation to the current ability of the municipality to implement and administer such choices. The study concluded that many municipalities seem to follow a reactive maintenance approach, whereby assets are run to failure. Jay Bhagwan, WRC executive manager for water use and waste management, says “When applying the 44% statistic to a comparative national base (consisting of 850 municipal plants), it would translate to approximately 374 plants that potentially have unsuitable technologies in place. This number is significant enough to support further investigation and measures to mitigate this as a key risk to sustainable and improved performance in the municipal wastewater services sector.”
The study indicates a history of issues relating to factors such as sewer pipe blockages, aging of the sewer infrastructure, vandalism of cables at sewer pump stations, design issues and maintenance backlogs.
The Department of Water Affairs’ (DWAF’s) wastewater services regulation programme has identified innovative approaches and appropriate technologies that might address these issues and ensure that sustainable choices are made by municipal decision-makers.
Membranes, through which water passes to be filtered and purified, are integral to modern water treatment processing. The pores of membranes used in ultrafiltration can be just 10 or 20 nanometres across – 3 000 times finer than a human hair.
But while membrane chemistry has been around for several years, it remains a source of intense research and development.
“Chemistry significantly contributes to innovative water treatment solutions, such as turning saltwater into freshwater suitable for human consumption.” – Yannick Fovet, head of global development for water, BASF
According to Burgess, membrane processes are playing an important role in water purification. These processes include microfiltration, ultrafiltration and nano-filtration for water and wastewater treatment.
Membrane processes are key components of advanced water purification and desalination, the continuous search for new materials and water purification technologies.
In its report, CEO 360 Degree Perspective on the Global Membrane-based water and wastewater treatment market, Frost & Sullivan says the market recorded a revenue of US$5,5 billion in 2012 and is estimated to reach US$12 billion by 2020.
According to Paulina Szyplinska, Frost & Sullivan’s energy and environmental industry analyst, new water treatment solutions are adopting membrane-centric approach to focus on water purity, wastewater reuse and recycling.
New technologies are often aimed at transforming wastewater into a resource for energy generation and a source of drinking water. Modular hybrid-activated sludge digesters, for instance, are now removing nutrients to be used as fertilisers and are, in turn, driving down the energy required for treatment by up to half.
According to the World Health Organisation, 1,6-million people die each year from diarrhoeal diseases attributable to a lack of safe drinking water as well as basic sanitation.
Water purification systems that use nanotechnology have become all the rage, especially in developing countries such as India. The technology removes microbes and bacteria from water using composite nanoparticles, which emit silver ions that destroy contaminants.
Reverse osmosis (RO) is a process of mechanical filtration to remove particles, absorb carbon and remove chlorine, taste, odour and chemical contaminants. The technology removes up to 99,9% of undesirable water contaminants by forcing untreated water through a semi-permeable membrane that separates down to .0001 micron. The reverse osmosis water purification membrane removes dissolved solids at the ionic level. Water pressure forces the water to flow in the reverse direction to the direction of flow in natural osmosis.
A total of 70% of the world’s freshwater is used by the agricultural industry.
Applying a more intelligent approach to water management by deploying precision irrigation systems, computer algorithms and modelling, is already beginning to bring benefits to farmers in developed countries.
Although holding much promise for the future, seawater desalination is still extremely expensive, with reverse osmosis technology consuming a significant amount of energy: about 4KWh of energy for every cubic metre of water.
Biomimicry mimics the biological processes by which mangrove plants and euryhaline fish extract seawater – using less energy than traditional desalination methods. Another approach is to use biomimetic membranes enhanced with aquaporin.
The findings from a recent Water Research Commission (WRC) and South African Local Government Association (SALGA) study indicate that 44% of the studied wastewater treatment plants may have opted for less suitable technologies when considering their resource base, capacity to manage and provide effluent quality requirements, whereas 33% technology options were questionable.
Scientifically speaking The Council for Scientific and Industrial Research (CSIR) pioneered an innovative water treatment process that reclaims high-quality precipitated calcium carbonate from calcium-rich industrial solid waste. The patented technology can also be used as a waste management tool that can create new enterprises in the water management sector, providing job opportunities and simultaneously reducing the amount of solid waste that could impact negatively on the environment.
High-quality calcium carbonate is useful for various specialised industrial applications such as gastric acid treatment, tablet filling in pharmaceuticals, plastics, paint and adhesives, and pulp and papermaking.
Additionally, the technology may offer a solution to acid mine drainage. The research group is focused on recycling technologies that would make the extraction of effluent cost-effective. The method appears to be effective with streamed water, although it is unlikely to be effective where groundwater is contaminated. Regulators need to take a holistic and strategic view of the implementation of the proposed technologies, based on the sustainability of the business of water services, and adopt design principles appropriate to the rural to small municipalities, providing leadership through their sector support and approval units.
Full thanks and acknowledgement are given to the Water Research Commission (WRC), CSIR, Rand Water and the Department of Water Affairs for the information given to write this article.