## 8 Conclusions  
While vast amounts of data are available surrounding chlorination and ozonation, the data surrounding plasma water and wastewater purification are greatly limited. Not all wastewater contaminants have been passed through a plasma reactor (such as manganese and iron), and the experiments that have been completed were performed by different researchers with different reactor designs. This implies different effectiveness values, efficiency values, energy yields, operating costs and capital costs. It is therefore difficult to formulate a comprehensive review of non-thermal plasma's capabilities. From the available data, it was concluded that it is feasible to retrofit existing chlorination wastewater treatment plants with non-thermal plasma technology to ensure the removal of contaminants of emerging concern (CECs). This is favourable for South Africa, where chlorination plants are popular. However, it was not feasible to retrofit an ozonation plant with plasma technology, as both produce similar disinfection by-products. This could cancel out the advantages of pairing the technologies in the first place. The coupling of chlorination and non-thermal plasma treatment provided the most effective contaminant removal (of the three possible combinations), and their combined capital cost was less than half the capital cost of a single ozonation plant, making it highly feasible. Unfortunately, the aforementioned combination had the highest operating costs and lowest energy efficiency. This reduces the attractiveness of plasma, along with its chances of large-scale implementation. We therefore state, from an application point of view, that chlorination plants can be furnished with plasma technology to achieve a combined (synergistic) treatment effect, with plasma units completing the treatment by removing the recalcitrant CECs. The combined process strategy is premised on the promise that it is possible to retrofit existing plants with sustainable plasma technology. Three recommendations can be made regarding the plasma reactor's feasibility: firstly, the energy yield of non-thermal plasma reactors should be improved. This can be achieved through increased research and improved designs. Secondly, the operating cost of plasma reactors should be lowered, and this can be realised by redesigning them to utilise renewable energy sources. Thirdly, lowering the cost of plasma reactors (perhaps by utilising economies of scale) can reduce both capital and operating costs, making plasma a more attractive investment. In addition, the decontamination efficiency of the plasma can be improved through further studies, leading to suitable reactor design and operating conditions optimization to suit practical applications. A final recommendation involves performing more research on contaminants of emerging concern. In the first case, the research should investigate how quickly CECs accumulate in the environment. This will provide an indication of the urgency with which plasma retrofitting should be approached. Secondly, the research should include determining the concentrations at which CECs become toxic to humans. This will provide us with both a timeframe and a maximum concentration limit and will ensure that the health of future generations is secured. The discussion and information presented in this manuscript clarify that with the envisioned success of plasma technology at the industrial level, a plasma treatment unit should be incorporated following chlorination to deal with the recalcitrant pollutants such as EDCs and chlorination DBPs. Plasma, based on scientific evidence, can degrade a wide range of pollutants including CECs and microbes, organic compounds [39; 71; 81; 82; 83; 109], inorganic residues causing water hardness [110], disinfection byproducts [43; 71] and others. No standalone technology can truly meet all wastewater treatment requirements (even at the tertiary level), but combinations/synergies will assure commendable desired results, with chlorination-plasma among the feasible options.