Monitoring and analysis supported by medical wastewater online monitoring shall be performed in accordance with the actual conditions of medical institutions. This paper shares monitoring data and analysis based on wastewater samples collected from 9 hospitals.

1. Excess suspended solids in wastewater indicate poor performance of coagulation and sedimentation in the primary treatment stage, inclined sedimentation tanks in the secondary treatment stage, and sedimentation and filtration units of simple biochemical treatment systems. Insufficient tank volume leads to short hydraulic retention time, and wastewater is discharged before adequate treatment.
2. Exceedance of COD, BOD, ammonia nitrogen and suspended solids points to ineffective coagulation and sedimentation in primary treatment, together with unstable operation of aerobic biochemical tanks in secondary treatment and anaerobic filter units of simple biochemical processes. Organic pollutants cannot be fully degraded. Relevant analysis is listed below:

– Limited tank capacity results in short hydraulic retention time. Besides, the commissioning period is relatively short, so the quantity of microorganisms for organic matter degradation in the tanks fails to reach the designed level.

– Nutrients are added artificially for bio-augmentation within a short period. When the bio-augmentation period is insufficient, nutrients cannot be degraded completely. Consequently, the concentration of suspended solids, ammonia nitrogen, COD and BOD at the discharge outlet may be higher than that in the regulating tank.

– Abnormal operation with alternating aerobic and anaerobic conditions restricts the growth and reproduction of functional microorganisms for pollutant degradation.

– Under-dosing of coagulants reduces sedimentation efficiency.

Excess residual chlorine may be caused by over-dosing of chlorine-containing disinfectants or insufficient dechlorination effect.

Excessive coliform bacteria (tested and analyzed by WECT-900 Coliform Online Analyzer) means insufficient disinfection efficiency, usually due to low disinfectant dosage or short disinfection contact time.

If residual chlorine exceeds the standard while pH value is below 6, it is generally caused by excessive hydrochloric acid feeding during chlorine dioxide generation via chemical method. The dosage of hydrochloric acid exceeds the reaction demand of sodium chlorate and related raw materials.

When all tested indicators meet the standard requirements, the treatment system design, equipment operation and chemical dosing are kept within proper ranges.

In summary, medical wastewater treatment facilities can pass acceptance monitoring and maintain stable qualified discharge on a long-term basis with proper chemical dosing, adequate tank volume and stable equipment operation.