Water Quality Improvement for an Urban World

Abstract

Water Quality is one of the most important factors in human health. Water quality is only growing in importance as infrastructure ages and areas become more urbanized. Growing population density adds stress to an already aging infrastructure, it is estimated that the average water system age is 45 years (Tabuchi, 2017). A consequence of this is a higher rate of failure as components of the system go past their recommended lifetime. A common failure is sewage overflows. Sewage overflows (SO’s) can happen in combined sewers or a sanitary sewer. When the SO happens in a combined sewer system (where stormwater and sewage is mixed) it is considered a combined sewage overflow. Our system targets either situation (SO or CSO). Both SO’s and CSO’s happen due to a larger volume of water in the system than the wastewater treatment plant can safely treat. When such events happen, the superfluous water is diverted from the plant and released (or stored when possible). Our design is placed at the outflow pipe to partially treat the wastewater. These sewage overflows are an issue as it releases pathogens into the environment, increases turbidity and, increases nutrients loading. Pathogens pose an issue for both downriver communities and aquatic life. The increased turbidity is linked to increased total dissolved solids; this increases the temperature of the system aswell as can reduce the capacity for photosynthesis. The design itself was started in the University of Michigan Center for Socially Engaged Designs’ Innovation in Action competition for 2021. The design takes into account the socially engaged design principals. As such it included conversations with stakeholders such as the wastewater treatment plant manager, rowers, business owners, aquatic biota experts, and downstream communities. The Quality Water and Contamination Control Unit is our design to reduce the many issues related to sewage overflows. Our design (further explained later) uses screening, granulated activated carbon, and UV. Screening is the first step and removes the large constituents. then it goes into the main body of where it meets three granulated activated carbon filters which reduce turbidity and many other constituents of concern such as chlorine, trihalomethanes, mercury, pesticides, herbicides, iron, lead, and bacteria. UV can reduce the pathogen load by 99.9% without creating harmful disinfectant byproducts. Statistical Hypothesis Testing via two One Sample t-tests were conducted to investigate whether or not a statistically significant relationship was in our prototype’s ability to reduce turbidity by a certain percentage accuracy while altering water flowrates would be present. The idea behind conducting these statistical tests would be so that results from them could be later used to further optimize and refine the physical structure of the protype in future prototyping design stages. Our design showed that around 40% reduction of turbidity was plausible though the testing was insufficient to make any definite conclusions. Our next steps include further testing of turbidity and flowrates of the current design, as well as adding coliform testing to ensure the expected reduction of pathogens is happening. Improvements to the design itself includes moving the outlet tube to the bottom of the body, adding the turbine and solar panels to make the system energy independent. Finally, adding a hatch at the top to make it easier to remove the filters for replacement or cleaning. The current system has potential to greatly reduce the issues related to sewage overflows.