Biofilm Formation and Effectiveness of Biosand Filtration Systems with Typical and Innovative Filter Media

Clean drinking water is a necessity and recycling stormwater and greywater has been more appealing in the recent decades to provide filtered water for drinking water and non-drinking water purposes. Biosand filters have been a popular filtering system of filtering potable water in developing countries, due to their simplicity in construction, reliability in operation and availability of constituent materials. The sand filtration system consists of diffuser rock, two sizes of gravel, and sand, which the container is constructed from concrete or plastic. Sand filtration system tend to struggle in removing specific chemicals such as nitrate and phosphate. Therefore, innovative materials can be added to the sand filtration system to increase the chances of chemical removal. Innovative materials such as biochar and bentonite clay were used to analyze their effectiveness in sand filtration system experiments. Biochar and bentonite clay have unique characteristics such as absorbing capacity and activated carbon, which remove suspended solids, chemicals, and toxins from contaminated water. Constant head permeability tests were used to simulate the sand filtration system in the lab. 15 tests were completed with different filter media arrangements, which incorporated two types of sand (coarse and fine), two sizes of gravel (small and large), biochar, and sodium bentonite clay. Contaminated water was created by simulating greywater by adding chemicals to reverse osmosis water. The pH, sulfate, chloride, phosphate and nitrate ion concentration removal were analyzed based on the contaminated water and filtered water. The hydraulic conductivity, filtration rate and pressure loss were also analyzed for each test. The tests that had the most effective result in terms of chemical ion removal, pH neutralization and filtration rate was the arrangement that included large and small gravel, fine and coarse sand, and biochar.