Redefining Water Treatment: Identification of WWTPs as an Earth System Problem and Circular Economic Eco-Bog System to Challenge It
Authors: Bilgin Adem , Erpul Günay 
Published: June 2021

Wastewater Treatment Plants (WWTPs) on the planet, daily processing billions of tons of wastewater and producing masses of sludge accordingly, act like artificial biogeochemical cycles themselves by producing material flow and creating microbial life cycles that normally do not exist in nature, a case with unknown cumulative long-term effects on the planet and human organisms. This study identifies WWTPs as a general Earth system problem with sub-problems to be challenged by new engineering techniques with an integrated natural science perspective. In order to challenge these problems, first the overall ecological role of WWTPs is clarified. Second a literature review (a) on the contents of the end products of wastewater engineering (b) on the effects of utilization of sewage sludge as fertilizer (c) on the utilization of sewage sludge as cement and construction material is provided. Current legal and practical situation in Turkey and EU is very briefly compared. Then, the design of the circular economic eco-bog system, which is a conceptual model of a new technology both to challenge these problems as much as possible and to act as an integrated industrial production system, is introduced. The new system is based on an innovative algaculture and ecomimicry of the evolution of wetland ecosystems from lake to terrestrial ecosystems. Algaculture and artificial bog components of the system use desulphurised fuel gases from both biogas component of the system and also concrete production component of the system. Desulphurization is to avoid H2S production in eco-bog unlike the natural bog ecosystems, and produce sulphurous fertilizers, and produce bog ecosystem services. Since, the fuel gas utilization from the biogas produced by archaebacteria is already net carbon zero, all system makes negative emission, namely sequestration. The CO2 to be released is fixed as biocarbon in algae in agriculture component, and then as organic and inorganic carbon after the sedimentation during accelerated evolution of eco-bog by creating hypoxia, acidification, and eutrophication conditions in artificial lake ecosystem. This sedimentation is mixed with sewage sludge ash for production of cement to have a higher quality concrete. Microbial biofertilizer and organic fertilizers are also produced from the algaculture component of the system, and industrial lichen from bog ecosystem. The system is inspired from lake death mechanisms of the nature, rather than lake health mechanisms in order to capture carbon and nitrogen in lithosphere and biosphere rather than releasing them to atmosphere as fuel gases, imitating natural bogs which are important carbon reservoirs. Finally, a new theorization of the issue is postulated as a way forward to reach SDGs, circular economy and bioeconomy targets of EU Green Deal as well as targets of RIO Conventions and Paris Agreement, not based on water quality arguments but based on mass and energy arguments, as well as arguments for ecologic health and preventive medical treatment for public health, and arguments for integrated industrial production in a holistic manner.