For hospitals, medical wastewater monitoring serves as an essential step to achieve safe discharge of treated wastewater. It helps avoid pollution of water resources at the source. This article introduces the standard workflow for medical wastewater treatment monitoring, which covers three key parts as follows.
- Arrangement of sampling points
Regulations in Hong Kong do not mandate sampling at the water inlet. However, inlet sampling points are recommended to evaluate pollutant removal efficiency and prevent intentional dilution before discharge.
Setting sampling points at the inlet of each septic tank creates heavy workload. Besides, the water samples show large concentration fluctuations and may not represent the actual water quality.
In contrast, the equalization tank can balance water quantity and water quality. Samples collected here are less affected by fluctuations in flow and pollutant concentration, delivering stable and representative data over a long period.
For the outlet side, sampling points shall be placed at the discharge outlet where the treatment system releases treated water to sewers or natural water bodies.
- Sampling schedule
Environmental authority monitoring generally includes acceptance monitoring, regulatory inspection monitoring and third-party commissioned monitoring.
Routine monitoring refers to self-monitoring conducted by hospitals. Hospitals without in-house testing capacity may engage qualified third parties for testing. Many hospitals have their own laboratory teams to carry out this work independently.
The discharge pattern of hospital wastewater varies between daytime and nighttime. Higher flow occurs during daytime with outpatient services, treatments, inpatients, staff and visitors. At night, discharge mainly comes from inpatients and on-duty staff.
A practical sampling plan is to collect samples every four hours, with three sets of samples taken daily from both the inlet and final discharge outlet. The plan can be adjusted flexibly according to the actual operation condition of each hospital.
- Key monitoring parameters
A set of standard parameters needs testing to verify safe wastewater discharge, including suspended solids, pH, COD, BOD and ammonia nitrogen. Two critical indicators are disinfectant residual and coliform bacteria.
Disinfectant residual reflects the disinfection performance. For example, active oxygen disinfection is increasingly adopted in this sector. An online active oxygen analyzer can track residual levels continuously to support proper disinfection control, avoiding insufficient or excessive disinfection.
