Nature-based Wastewater Treatment Systems: An Overview of the Challenges of Small Capacity Plants in an Urban Environment

With the growing population and rapid industrialization, water shortage is a serious problem for mankind. Every solution that provides usable and fresh water to those in need is important. No source of water can be ignored in the persuasion of a sustainable water supply. With this in mind, the feasible and economically affordable treatment of sewage water concept emerged. As one study indicated, out of 72,000 MLD of wastewater that is generated in India, only 44% of it receives treatment. As freshwater sparsity increases day by day, it has become common to treat used water for use by humans for daily needs, animals, irrigation, and industrial processes. As such, various unique and efficient treatment methodologies have been developed by researchers and professionals worldwide. But these treatment methodologies have given rise to serious environmental threats in terms of disposal issues which cannot be ignored in the focus of the circular economy. As mentioned by Barry Commoner, a famous American Ecologist, and Biologist, the environmental cost of these treatment methodologies is enormous—be it energy cost, solid waste disposal cost, or land cost. Environmental innovation that promotes nature-based technologies jeopardizes firms’ profitability and sustainability of the treatment in the long term. This hesitation toward change is interfering with the widespread adaptation of NbS. It has been proven that NbS is far better at tackling stakeholder satisfaction, long-term effects on the environment, reducing capital cost, and operation-ease adaptability of the system as compared to the latest technologies. The areas where NbS lacks advantage are automation, remote operation, and maintenance, real-time parameter monitoring. There is also little research on handling toxic materials, in highly turbid and saline waters. Further research is needed in these areas. This is also a challenge to the policymakers to develop the construction guidelines and operating standards which will suit the local environment and demands of NbS. This is necessary to legalize the construction and operation of these systems. When the question of adaptation of green technologies or circular economy surfaces, many industries prefer to adopt the 3R technique in their production methods, resulting in treatment technologies generating high quantities of solid, liquid, and gaseous waste. It has been documented that the adaptation of NbS leaves a negative impact on the industrial economy. These technologies pose quite a challenge in terms of land and the reuse of treated wastewater. The main reason is that there is no consistency in inlet quality and quantity of water. As the inlet water quality and quantity are unpredictable, the outlet water quality is unreliable. While this problem can be solved by imposing responsibility on any particular department or private authorities, the effectiveness of the measures is questionable. This chapter discusses the various problems public authorities, lawmakers, and industrialists face. It also discusses how they are addressed in various parts of the world, and how with proper research, further improvements can be made.