Investigation of grey water treatment performance in a vertical subsurface flow constructed wetland

Abstract

The depletion and unconscious consumption of water, which is an indispensable element for vital activities, has become a global problem due to the increasing world population and industrialization. The decrease in precipitation as a result of climate change has made this problem even more challenging. A significant portion of the world's population currently has difficulty in accessing potable clean water resources. Moreover, it is reported that there will be a further increase in this human population deprived of this water in the coming years. Although countries put forward strategic plans on a national and international scale so that this problem does not turn into a serious crisis, they will face this crisis unless more measures are taken. The sustainability goals of the United Nations are a part of the solution proposals put forward against this problem. As resources should be used correctly and efficiently, making these resources reusable is one of the most important solutions. The reuse help reduces the risks of negativity in the process leading to the water crisis. Treatment of GW, which constitutes a large part of domestic WW and has a low pollution load, for reuse will reduce the burden on existing facilities and contribute to sustainable wastewater management. Thus, treated WW, which is discharged into water bodies and has the potential to cause environmental pollution to a certain extent, will turn into a valuable input. The treatment of these GWs, which do not require advanced treatment, using natural treatment technologies will further increase this positive contribution. Because natural purification technologies; They can imitate natural processes and offer an effective treatment performance without requiring energy, reinforced concrete structure and mechanical equipment. For all these reasons, in this thesis, the conversion of gray water into reusable water using a natural treatment technology has been examined. GWs, which are characterized as weak or strong according to their type, have a great potential for reuse. GWs can become usable water directly or indirectly by removing the disease-causing pollutants and pathogens in its content. Thus, the pressure on water resources may decrease somewhat. Moreover, since the load on WW treatment plants will decrease, a serious economic loss will be prevented. In this study, the treatment of GW, which is a valuable resource, by collecting it with discrete systems for reuse in CWs, which is one of the natural treatment systems, was investigated. Thus, it is aimed to fill this gap by offering a sustainable and environmentally friendly treatment method for Türkiye, which is also under water stress. Presenting it as a realistic solution to prevent environmental disasters such as mucilage will also be decisive in terms of Türkiye's environmental policies. By obtaining effective treatment efficiencies, an incentive will be created for the use of these technologies, especially in areas with low urbanization. In this direction, the GW of a large hotel in Taksim, Istanbul, was collected and then characterized, and these GWs were treated in the vertical subsurface flow constructed wetland (VFCW) installed in the laboratory. The quality of the treated GW in the reactor was determined and thus the GW treatment performances of the wetland were investigated. Characterization results were compared with a previous study by TÜBİTAK and no big difference was observed. However, the decrease in the number of guests due to the pandemic caused a decrease in N and P values. On the other hand, higher than average values were obtained in some COD measurements due to their lower water consumption. The VFCW bed, where filtration and adsorption will take place, was created by considering the design concepts in the literature. The system was fed with gray water for 2 weeks before the main experiment plan was carried out. Thus, biofilm growth was provided for the activity of microorganisms. The reactor in which Cyperus alternifolius was planted was fed with GW for 4 hours until saturation throughout the operation.