The tofu production process produces liquid waste, where the waste contains high enough proteins and can decompose. However, suppose the waste is not processed correctly before discharge into the river without passing through the decomposition. Then, it will damage the biota due to changes in pH value. The liquid waste treatment could decrease the Total Suspended Solid (TSS), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). Thus can be beneficial as a hydroponic nutrient solution. Currently, pH control in large-scale tofu factories still uses manual means. This method can pose a risk of delays during pH checking. The problem made UNY students create tofu liquid processing waste automation using an automatic pH detection control system. They are Muhammad Ikhsan Ardi Hansyah, Hilal Fahruh Hamam, Ersa Ivadany, Fitria Alsya Yasmin and Chayyu Zalena Hawie.

Tofu liquid waste comes from soaking, washing, milling, boiling, and filtration waste. If not treated properly before disposal, this waste can damage the surrounding natural environment because this liquid contains high enough protein levels. If not processed first, it will cause a foul odor. If discharged into the river, it will make environmental pollution severe enough. It can have a fatal effect on river biota.

Meanwhile, solid waste (tofu pulp) is beneficial for animal feed. This tool utilizes Arduino as a controlling relay device, LCD, pH sensor, Turbidity sensor, and TDS sensor. The potential of Hydrogen (pH) is a water quality parameter that indicates an acid or base solution with some hydrogen or hydroxyl ions, which can provide plant nutrients. This technology develops a pH-level detection automation tool in liquid waste. The known plant automatically controls the pH of the trash to fit standard design criteria.

Ersa Ivadany explained that the microcontroller is connected with sensor hardware assembly. The data processing section consists of microcontroller hardware, RTC, and SD Card. All of these components connect to a microcontroller via a jumper cable.  Once all the devices connect into a container made of box-shaped acrylic plastic, all devices are safe from dust or water that can damage components. The action treatment section of the output data consists of LCD hardware, relays, and actuators. Finally, an installation of LCD relay the microcontroller through jumper cable.

This work recently won a Gold Award and a Macedonian Special Award in the World Youth Invention and Innovation Award. This work is one of UNY's efforts in the sustainable development agenda in quality education and safeguarding urban communities. (Dedy, ts-Waryati, Alina)