The researchers tested using chitosan and alum to clean up sewage. They found that a mix of both at a 1:1 ratio worked best, removing 64% of the dirt in the water. This mix also helped get rid of harmful chemicals in the sewage. The best pH level for cleaning was 7.1. Using both chitosan and alum together could help clean sewage more effectively and with less chemicals, which is good for the environment and saves money.