Biological wastewater treatment is mainly dependent on the actions of microorganisms that can be used to treat wastewater. Microorganisms will start to stick together when they degrade the organic matter in wastewater for food and flocculate to settle the pollutants. This study aimed to investigate the effect of food to microorganism (F/M) ratio and iron in a biological process using aerobic treatment. For this purpose, four aerobic tanks (A, B, C, D) were set up using activated sludge as the seed sludge, air pump as air diffuser to provide oxygen to the system, and three litres of synthetic medium as carbon source for each tank. A specific amount of iron (II) sulfate was added into tanks B, C, and D with the weight of 3 g, 6 g, and 9 g, respectively. Tank A act as a control, and no iron dosage was added. The F/M ratio for tanks A, B, C, and D were 0.8, 0.5, 0.4, and 0.3 mg BOD/mg MLVSS, respectively. The aerobic tanks were operated for 40 days in sequential batch mode and sampling was collected four times per week to observe the COD and MLVSS. This study has found that Tank D shows the best performance compared to all tanks with 84.71% COD removal efficiency and a fivefold increment of microorganism growth rate. These findings suggest that a relationship exists between the iron and F/M ratio to enhance the aerobic treatment process.
