Effects of Liquid Wastes from Tofu Industries on Water Quality in Parangan River, Magelang District, Central Java-Indonesia

Continued entries of liquid wastes generated by tofu industries into nearby rivers might deteriorate the water quality if disposed of without prior treatments. The research objectives were to determine the liquid waste quality from tofu productions near Parangan River (Magelang, Indonesia), assess the river water quality and investigate the effects of the liquid waste on pollution load and water quality status. With this information, the research can help determine pollutant load allocation in the river and provide the basis for formulating water quality management policies if it is not contaminated or pollution controls if otherwise. This research employed purposive sampling, direct measurements in the field, laboratory tests, descriptive-comparative analysis, mass balance and pollution index method. The results showed that the pH, temperature, COD, BOD, TSS and ammonia levels of the liquid wastes had surpassed their maximum permissible levels. Similarly, the river's COD, BOD and ammonia contents did not meet the water quality standards. With BOD, a pollution load indicator, exceeding the total maximum daily load, the water quality statuses at monitoring points S2, S3 and S4 were categorised into slightly polluted. It means that the liquid waste generated by the tofu industries has detrimental effects on the water quality of the Parangan River.