Urban Stormwater Treatment with Ultrafiltration and Pulsatile Fluid Flow

Abstract: Stormwater can be a potential water resource that has high quality before it reaches surfaces and becomes runoff. Various pollutants, nutrients, and microorganisms can enter runoff that normally flows to receiving waters. Stormwater contaminants can vary depending on the time and place, as the contaminants come from different sources and sometimes the quality of stormwater can also deteriorate during the collection and storage. Therefore, treatment of stormwater is necessary before reuse and also before discharge into the environment. Various methods can be used for this purpose. Ponds, wetlands, and bioretention systems are used on a small scale in various countries to remove pollutants from stormwater. In addition to these methods, the membrane process for stormwater treatment has attracted much attention. The application of membrane technology in new areas such as stormwater treatment requires a great deal of research to evaluate the opportunities and challenges in advance. Various research were being conducted to separate one or more pollutants from stormwater using membranes. However, more research is needed to evaluate the applicability of membrane processes in the field of stormwater and to cover other aspects of the membrane process, challenges and advantages. For this purpose, two different types of stormwater were collected at different times of the year. A mixture of urban snowmelt water was collected and used to evaluate the quality of the treated snowmelt water sample and the possibility of reuse according to regulations in different countries. Another concern was about the fouling in the membrane and the productivity of the membrane process for treating heavily contaminated snowmelt water sample. Therefore, pre-treatment and pulsatile fluid flow were added to the system. To achieve efficient membrane cleaning, backwashing was performed at regular intervals and different backwash times and two chemical leaning combinations were used. In the end, the quality of the backwash water from the membrane cleaning was characterised, which may be helpful in the future in finding a method to maintain the backwash water. As the frequency of pulses increased, the productivity of membrane process increased significantly (from -0.4 to 10.6 LMH). In addition, the treated snowmelt mixture can be used for various applications, such as wetland maintenance, toilet flushing, and municipal use. If the treated stormwater is disinfected, it can also be used for reuse as drinking water. Although the reversibility, backwash efficiency, and permeability were higher with a backwash of, the optimal backwash duration was 45 s, depending on productivity, and the use of the chemical combinations (either NaOH, NaOCl, HCl or NaOH, HCl) could restore the membrane permeability to 107 LMH bar-1. Characterisation of the backwash water showed that this water contains a high concentration of TSS, TOC and total metals. If stormwater treatment using membrane is to be used on a larger scale, the backwash water must be considered because it will have large volumes. Methods such as coagulation, evaporation, and flocculation can be used to separate of pollutants from the backwash water.