## 4 Discussion
In addition to providing a larger storage capacity to supply other potential industrial water demands in the surrounding areas, the existing tanks should replace the 90 m\({}^{3}\) underground reservoir planned by the project, thus considerably reducing the total cost of system installation and, therefore, the final cost of the reclaimed water. Other less tangible aspects involved in the operation of water tank trucks that negatively impact the standard of living of the population in the region should also be mentioned. The intensification of water tank truck traffic would increase noise and air pollution levels, as well as contributing to the premature deterioration of road paving, and increasing the risks of accidents [38]. In addition to being more economically viable, the two alternatives using reclaimed water could provide several environmental benefits, such as reducing annually the discharge of more than 2 tons of organic matter and 1.5 tons of Nitrogen and Phosphorus, considering only in the case of the Alegria WRP/WTP system [34]. This reduction would be especially important since the receiving water body of these effluents is the Cunha Channel, considered to be the most polluted stretch of Guanabara Bay, an important estuarine system already under strong environmental stress [47; 48]. From a water security perspective, implementing the use of reclaimed water would support the necessary shift from a conventional model based on already saturated conventional supply systems to a water supply matrix with more sustainable and resilient systems [13; 15], therefore increasing water supply security, especially in water stressed regions [14; 49]. Recurrent periods of water scarcity coupled with the prohibitive water costs of the conventional water supply systems justify the global growing trend in which major corporations are seeking alternative water supplies, among them the employment of reclaimed water [50]. In particular, in the last two decades, companies such as Coca-Cola, Ambev, Arcellor Mittal, Santista, and Fiat-Chrysler have been investing in changing their water supply matrix aiming at greater water security, by rationalizing the use of water in their production processes and prioritizing more sustainable water supply alternatives such as wastewater reuse systems [50]. According to [49], the use of reclaimed water has the potential to promote economic growth and improve urban health conditions and social welfare, therefore configuring a public policy of relevant interest to society. However, the comprehensive implementation of wastewater reuse in the MRRJ requires a review of the current water permit values, especially in areas usually not affected by water scarcity. The present value of the Public Unit Price (PUP) for industrial water supply in the studied watershed is BRL'0.055 (USD 0.011) per m\({}^{3}\)[51]. It corresponds to less than 0.1% of the estimated cost of the most viable alternative presented by this research (BRL 5.27 or USD 1.07 per m\({}^{3}\) for reclaimed water delivered by pipeline), therefore considerably reducing the attractiveness of reclaimed water supply for industries and other potential consumers. Although it was not in the scope of the present work, the need for risk assessment in wastewater reuse projects should be investigated [15; 52]. This is particularly important because the project comprises = non-potable reuse and it should be tailored according to the purpose of water reuse.