The Public Health Study Program, Faculty of Health Sciences (FIK) Muhammadiyah University of Surakarta (UMS) held a guest lecture together with the Central Java Health and Medical Equipment Testing Laboratory Center. The guest lecture will be held on May 31 2023 at 08.30-09.10 WIB via the Zoom Meeting platform. With Mr Sudarwin. ST. M.Kes, representative of the Central Java Health Laboratory and Medical Device Testing Center, students of the UMS FIK Public Health Study Program in the Water Safety course discussed material regarding DO and BOD. This public lecture activity teaches students regarding DO and BOD testing, where this testing can be carried out using three methods, namely titration, dilution and respirometrics. The students who attended the guest lecture were quite enthusiastic, with quite a lot of students asking questions and sharing their experiences during the discussion session.