An analysis on grey water source separation as an alternative for conventional wastewater management using the case of Kocaeli Yenikent neighborhood

According to World Population Prospect Report published by United Nations, the global population is projected to increase by more than one billion people over the next 13 years, reaching around nine billion in 2030, and to increase further to 10 billion in 2050 and around 11 billion by 2100. In spite of this rapid population increase and urbanization, available water sources remain the same and undoubtedly global water scarcity will pose a risk. As opposed to popular belief, Turkey has been sharing global water stress and approaching physical water scarcity according to the reports published by UNESCO and DSI. Although one of the initial steps to prevent the water stress is conservation and efficient use of fresh water resources, in recent years, domestic wastewater is being considered as an alternative water source. Instead of recovering entire domestic wastewater, stream segregation and ECOlogical SANitation (ECOSAN) approaches enable to collect less polluted streams of domestic wastewater. Within the framework of these concepts, it is possible to collect domestic wastewater streams in two ways. While stream segregation allows the separation of toilet wastewater from other domestic wastewater streams as two streams (grey water, black water), ECOSAN concept involves separation of domestic wastewater into three parts (grey water, yellow water, and brown water) components. Grey water refers to wastewater originated from shower/bathtubs, wash basins, washing machines, sinks, and dish washers. Sub-streams of grey water also defined in two groups as weak (light) grey water including bathing and hand wash wastewater and strong (dark) grey water consisting of basically kitchen wastewater (sink and dish washing) and washing machine wastewater. Grey water is considered as a valuable water source as it constitutes about 70-75% of total conventional domestic wastewater volume with lower pollution content compared to conventional domestic wastewater. Due to its high volume and lower pollution, grey water is considered as an alternative water source. In this study, stream segregation focusing upon grey water was investigated within the scope of environmental, financial and social sustainability through an appraisal of technical and economical applicability and public acceptance, in an attempt to contribute to grey water management and reuse. As a sustainable and alternative water source, characterization of grey water and its sub-streams were overviewed and evaluated, and a summary table that indicates typical ranges of each stream was created. Similarly, grey water treatment methods and quality criteria based on various end-uses were examined in detail. Current situation of wastewater management in Turkey, as well as in Kocaeli, was reviewed in terms of conventional wastewater management and wastewater reclamation together with examples of existing practices. The steps for the implementation of grey water reuse systems were determined by using the example of selected study area as the following; - Selection of the study area, - Determination/Prediction of volume and characterization of grey water and its fractions, - Determination of possible end-use potentials and volume of water demand for these end-use purposes, - Selection of quality requirements for specific end-use purposes, - Selection and design of treatment method. As a result of comparison and matching of grey water generation and demand in terms of quality and quantity in the study area, four different scenarios that indicates grey water reclamation for toilet flushing, cooling, street and car wash were developed and analyzed within the scope of technical and financial applicability and public acceptance. For the financial assessment of scenarios, capital expenditure and operational expenditure of selected treatment methods were calculated. While the capital cost of each system included the costs related to in-building plumbing, distribution pipes of treated grey water, and treatment units; operational costs were arising from electrical and chemical consumptions. The capital expenditure of each scenario was compared with the investment costs of similar capacity conventional systems. Flow charts, water balances and budgets of existing wastewater management system and alternative sustainable systems indicated by scenarios were developed. Operational expenditures of current system and each scenario were calculated and analyzed by using these flow charts and water budgets and compared with each other. Within the scope of financial analysis of scenarios, pay-back periods were also calculated. Similarly, flow charts and water balances were used to estimate the possible water savings in the case of implementation of scenarios. To evaluate the social sustainability of grey water reclamation systems, a preliminary survey was conducted and the levels of acceptance of grey water reuse, background knowledge on grey water, and awareness of water scarcity were questioned. The results of this work revealed that saving of fresh water sources and operational cost could be achieved due to the seperate collection of grey water on its source and reuse. As a result of the case specific assessment of scenarios, water savings could reach to 100%, while the savings could range 15-35% in terms of operational expenditures. From the point of pay-back periods, the results showed that the pay-back periods were comparatively shorter for the grey water reuse in industrial facilities that were located nearby. Within the scope of scenarios, grey water reuse on toilet reservoirs, which is the initial on-site end-use purpose, was reasonable to be implemented in new building projects instead of existing ones. In addition, the results of this work, the data that gives insight about the environmental, social, and economic viability of grey water reuse was used to produce a guideline (Appendix D) that indicates the method and systematic of implementation of source separation of grey water.