Civil Engineering June 2021 | Vol 29 No 5

Civil Engineering June 2021 21 it into the City’s water supply upstream of a conventional water treatment plant. RECENT TECHNOLOGICAL INNOVATIONS An important aspect of engineering is the need to adapt our thinking to the evolution of technologies, understanding not only that engineering drives tech- nology, but that technology also drives engineering. At times, we must reconsider the narrative regarding what technology is seen as the default and essential. This is particularly evident in the world of water reuse, where faith in reverse osmosis (RO) filtration as the ultimate bar- rier against contaminants is unparalleled. However, by defaulting to designing an entire water reuse scheme around RO we risk missing out on opportunities for a more reliable, affordable, energetically optimised, and environmentally responsible solution. In the last decade there has been a move towards adopting alternatives to RO that rely on biological (living) processes, together with other technologies, to en- sure safe removal of contaminants. These alternatives can significantly reduce the energy requirements of the treatment process, eliminate the need to concentrate the contaminants in a saline brine waste stream that must be returned to the environment, and are potentially cheaper to construct and operate. For the City of Cape Town, the incor- poration of such technologies substan- tially reduced the projected levelised costs of water reuse to be comparable with groundwater options, and significantly cheaper than seawater desalination. 1 PARTNERSHIPS AND STAKEHOLDER ENGAGEMENT The lessons learned from global water reuse projects confirm that such projects require a substantial and collaborative effort to engage diverse stakeholders to be successful. People have obvious questions about drinking water reuse, and these need to be heard and addressed. South African cities are fortunate to be able to leverage extensive experience and ex- pertise from, and collaborate with, a global network of designers, scientists, operators, and communications specialists working in the water reuse industry. Planning and implementing water reuse has become the new normal for many dry regions and cities, like Windhoek in Namibia or California and Texas in the USA. The SANS 241 drinking water quality standard does not yet address all the risks inherent in purifying treated wastewater. Planners and designers therefore need to work with monitoring and compliance laboratories to establish a risk-based ap- proach to setting targets for water quality, based on water source quality and specific contaminants of concern. The City of Cape Town, for instance, has agreed to monitor and test for over 250 different water quality parameters. The designs for purification processes need to be conservative, employing mul- tiple barriers that collectively ensure ad- equate removal of harmful contaminants, based on the removal efficacy they have proven in practice. To ensure that the treatment processes are doing what they are designed to, strict monitoring and control protocols are required (guided by recognised methodologies such as ISO 22000 and HACCP). The planning and design of water reuse schemes requires multidisciplinary skills – far more than for conventional surface water projects. Engineers, water quality scientists, environmental prac- titioners, operations and maintenance teams, and communications departments all need to work closely together to steer the project from every angle. If the project team can establish the organisational responsibility structures and reporting protocols at the beginning of the project, it will ensure that all deci- sion makers are well aligned throughout the planning and design process. This may necessitate building partnerships across institutions, disciplines, and dif- ferent spheres of government. Lastly, and most importantly, stake- holder communication is critical to the success of the project and needs to form an integral part of the project’s planning and design. A clear strategy will guide the team during stakeholder engagements and ensure that messaging about the proposed scheme is clear, concise, and consistent. The City of Cape Town has spent over a year engaging stakeholders and preparing public communications materials (in- cluding videos, presentations, brochures, maps, and fact sheets) which have all been made available on the City’s website . MORE THAN STEREOTYPICAL ENGINEERS South African engineers are now able to leverage global (and local) experience in advanced water purification to support municipalities in developing plans and designs for city-scale water reuse schemes. In the face of a changing climate, severe droughts, and growing urban development, we have to be more than just stereotypical engineers. We have to find ways to respect nature’s limits, while making better use of the precious resources we have.  REFERENCE 1 CCT Water Outlook 2020. Daniel Petrie works for engineering and advisory firm Zutari, which assisted the City of Cape Town in developing its plans and designs for the proposed Faure New Water Scheme, a 100 Mℓ/day city-scale potable water reuse project. Water source Ozonation BAC GAC Ultrafiltration UV/AOP Media filtration Ultrafiltration Reverse osmosis UV-AOP Remineralisation Disinfection Drinking water Activated carbon filtration versus RO based purification processes (Credit: City of Cape Town) Water source Drinking water