Introduction

1. Rainwater Wastewater treatment plant Potable Water Conventional toilets (1.6 gpf) and urinals (1 gpf) Wastewater Centralized vs. Decentralized Sanitation Technologies: Energy and Global Warming Implications ChirjivAnand,(chirjiv.anand@rockets.utoledo.edu),Dr. DefneApul, (defne.apul@utoledo.edu) Department of Civil Engineering , University of Toledo, Toledo, OH Abstract Results and discussion The drinking water and wastewater infrastructures in the US are degrading and there is a serious shortfall of funds needed, in the next few decades, to meet mandates of Clean Water and Safe Drinking Water Acts. In addition, the current water infrastructure is very energy intensive. One solution for addressing these issues is implementation of integrated water management systems in buildings that use less potable water and send less water to sanitary and storm sewers, to benefit from the reduction of energy use to treat the amount of water being sent to the waste water treatment plants. Implementation of the most sustainable alternative to use of potable water for flushing toilets, to a large set of buildings in an area, can significantly help reduce the energy use, cost and also carbon emissions over a period of time. The focus of this research is comparison, using an input output life cycle assessment approach, of existing alternatives, to use of potable water for flushing toilets at Nitschke and Palmer buildings in the University of Toledo. The alternatives compared are i) Conventional toilet systems ii) Low flush toilets iii) Rainwater to flush conventional toilets iv) Rainwater to flush low flush toilets ,and v) Composting toilets, based on the following criteria, a) potable water demand b) energy use and c)carbon emissions, in each case. All these technologies have been used before for flushing toilets but never been compared using a life cycle assessment approach. A 100% reduction in potable water demand was observed in rainwater and composting cases along with least energy use and carbon emissions and could cut off the building from the centralized treatment plant for toilet flushing purposes. All the alternatives considered were economically and environmentally better suited when compared to conventional systems. Introduction • Aging and degrading U.S water infrastructure-Many built over a hundred years ago are leaking, collapsing, and overflowing. • Funding gap-of $23 billion a year between current investments and the investments that will be needed in the next 20 years to meet mandates of Clean Water Act and Safe Drinking Water Act. • Flushing water quality is the same as drinking water quality. • Water treatment process-energy intensive • Ex: More than 1.879 million dollars in 2008 , spent towards electricity bills and usage- City of Toledo, waste water treatment plant. • Annual operation cost- 17 million dollars (not counting capital improvement), City of Toledo, waste water treatment plant , 2008 for total annual raw wastewater treated =  28.034 billion gallons. • Proposed solution –alternative sanitation systems (decentralized technologies) Figure 3. Construction and operational cost Figure 2 .Potable water demand for all scenarios • Objective: Evaluation of five different sanitation scenarios that can be implemented in institutional buildings, based on a )Potable water demand, b) cost, c) Energy use, and global warming potential Methods: Table 1. Inventory Table • Buildings chosen to compare the alternatives – Nitschke and Palmer buildings ,University of Toledo • Life cycle Assessment software- Economic Input Output Life Cycle Assessment (EIOLCA) • System boundary -entire U.S economy. • Functional unit- provision of sanitation services for 3200 people that use NI and PL buildings in • one year. • LC phases included in inventory analysis– a) Construction b) Operation • LCA input – Cost for each phase • Figure 4. Energy use in Tera joules of construction and operational phase of each scenario obtained from EIOLCA Figure 5. Carbon emission values in Metric tones of carbon based on cost for each scenario obtained from EIOLCA for the construction and operational phase. Potable Water Wastewater Conventional toilets (1.6 gpf) and urinals (1 gpf) Potable water demand: Figure 2. Shows the decreasing demand of potable water from conventional to composting toilets. Cases 3 and 4 replace the water demand with rainwater, but send the same amount of water as cases 1 and 2 to the wastewater treatment plants Cost: Though the construction costs of the centralized systems are less than those of the decentralized systems (Figure 3), due to comparatively lower operational costs, these systems pay off the initial construction costs within a period of about 1 and 3 years in case of composting toilets and rainwater low-flush cases respectively. The pay back period is highest in case of rainwater conventional systems. Energy Use and carbon emissions: The energy use and carbon emissions from decentralized scenarios is found to be higher compared to conventional and low flush cases for the construction phase due to use of additional components such as cisterns, composting units and pipes. Similar to the cost the energy use and carbon emissions from the operational phase are lower for the decentralized systems operational phase . With respect to both energy use and carbon emissions the rainwater conventional scenario has the highest pay back period , due to its high initial construction cost. A cost reduction in the components of this case could make it a better suitable scenario. Water treatment plant Case 1 Conventional systems Wastewater treatment plant Low flush toilets (1.28gpf) and urinals (0.5 gpf) Potable Water Wastewater • Case 2 Low flush systems Conclusions: Water treatment plant Wastewater treatment plant Water treatment plant • The comparisons of scenarios based on cost, energy and carbon emissions show the same order in results though different in magnitude (figures3, 4 & 5). This suggests a direct linkage between the cost, energy use and carbon emissions. A decrease therefore, in cost would help reduce the energy use and carbon emissions. The energy use and carbon emissions for all the sectors are directly proportional to the total cost. • Composting toilets were found to be the best choice based on the potable water demand , energy use and carbon emissions among all the five cases with the lowest payback period . • Use of rainwater to flush toilets was found to be the second best alternative to potable water as the buildings have the potential of collecting the amount of water required to replace the entire demand. With a reduced flush rate this technology can be well made use of in institutional buildings. • The energy use, cost and carbon emissions in case of conventional toilets are less compared to alternatives cases but only for the initial construction phase, the operational phase is costly and also has the worst energy use and green house gas implications. • Case 3 Rainwater in conventional systems Rainwater Potable Water Low flush toilets (1.6 gpf) and urinals (1 gpf) Futurework • Case 4 Rainwater in low flush systems Wastewater Water treatment plant Wastewater treatment plant • Future work would include : • Comparison of grey water technology with rain water, composting and low flush systems . • Considering technologies in combinations Ex: using rainwater in foam flush composting toilets. • Developing sustainability metrics and comparing these alternatives based on these metrics. • Possibility to obtain LEED credits using these methods. • Assessment of other integrated water management options like -treatment and reuse of grey water, treatment and reuse of black water, green roofs, rain gardens ,condensate recovery . Human waste Composting toilets and waterless urinals Compost Case 5 Waterless systems Acknowledgements : This project is being funded by Water Resources Research Institute, Ohio Water Resources Center and Lake Erie project fund Figure 1. Sanitation scenarios at Nitschke and Palmer buildings