Coagulation and Filtration Methods on Tofu Wastewater Treatment

he tofu industry is a small industry (home industry) that produces wastewater between 100-200 times the allowable limit and is usually discharged directly into water bodies, thus polluting the environment. This study aims to combine the coagulation method (stage 1) using Polyalumunium Chloride (PAC) with filtration (stage 2) on several variations of materials (quartz, activated carbon, and zeolite). The study was conducted with six replications. The comparison of waste quality (BOD, COD) was observed at each stage of the study. The SAS 9.4 was used for data analysis, including the application of the T-test and ANOVA. The study found that coagulation with PAC 690 mg/L reduced BOD by 51.7% and a dose of 765 mg/L by 61.1%. In the COD parameter, the reductions were 65.84% and 67.55%. In the second stage (filtration), the reduction in BOD was higher in activated carbon (79.33%) compared to zeolite (78.67%) and quartz (75.46%). Activated carbon also had the most COD reduction effect (73.22%). Although the statistical results showed significant differences in all doses and media, the use of 765 mg / L PAC and activated carbon filtration had the most effect on reducing BOD and COD of tofu industrial wastewater. This research can be used as an alternative in the physical processing of tofu industrial wastewater.