Study and Design of a Sensor System for the Detection of Illicit Discharges in Sewers and Water Bodies

Abstract

The use of water in our society is of great importance. This is used not only for human consumption but also for industrial and livestock activities. Once the water has been used and is no longer helpful for the activity, it becomes a waste called residual water. These waters contain substances that endanger human health and ecosystems. To reduce environmental damage, there are treatment plants that treat these waters to reduce their levels of contamination. We can find two types of sewage treatment plants, those that purify water from urban centres and industrial sewage treatment plants. Industrial treatment plants are responsible for reducing the contaminant load of the water so that it can be discharged into the public sewer system or into the environment.The presence of illegal discharges and overflows in the sewage system pose a threat to water bodies. Illegal discharges occur when a company or person discharges a volume of water into the sewer without authorization. These discharges can cause a drop in the performance of the treatment plant, which will cause an effluent of poorer quality. On the other hand, overflows are generated when the sewer cannot carry all the water that enters and it is necessary to use the sewer overflows. Overflows can cause pollution of water bodies. In many cases, it is not possible to detect who is responsible for the spills. What makes these go unpunished violating the environmental principle of that whoever pollutes pays.To solve this problem, the development of a low-cost system for monitoring water parameters to detect problems in sewers within the context of smart cities is proposed. Our working hypothesis is that in the presence of a discharge, the concentration of specific water parameters will change enough to be detected. When the site of the spill is detected, it will be possible to quickly go to the place in order to stop the spill in addition to taking the necessary legal actions against the person who is carrying out the spill.For our system, we have compiled information on the different parameters that are incorporated into other systems to monitor sewage, such as water level, temperature, conductivity, turbidity and other water contaminants such as organic matter, nutrients, pH and heavy metals. With this information, we have determined that the most exciting parameters that we are able to measure at a low cost are temperature, conductivity, turbidity, water and oil level. In addition, the use of rain sensors for storm sewers is included.To monitor these parameters, low-cost commercial sensors are chosen to monitor temperature, level and rainfall. For the other parameters, the low cost commercial options that currently exist are not helpful. That is why we decided to develop our own sensors. We decided to use inductive type sensors for conductivity and optical sensors for turbidity and oil control.Regarding the inductive sensors, we have determined that there are interferences of the solids and the water level in the response of the sensor. We have verified that t...