PSC detention due to in-operational Sewage treatment plant

What happened

During a recent AMSA PSC inspection, one of our fleet vessels Sewage Treatment Plant was observed to be in-operational, vessel was detained with the following deficiencies:

1. Lack of adequate water level in the biofilter tank.
2. Disinfectant / Sterilization tube choked.
3. Sewage three-way inlet valves (2 in no’s) found seized.

Root cause

Lack of proper maintenance of STP

Corrective actions

Repairs were carried out on priority basis to reinstate the Sewage Treatment Plant and to release the vessel from AMSA’s detention order. Class and flag were called for attendance and inspection.

Preventive actions

In order to avoid such observations following preventive actions to be carried out regularly:

OBS # 1: Lack of adequate water level in the biofilter tank.

Check the water level in the biofilter tank and the bubbling action. The biofilter tank should always be full of water and bubbling action should be visible. Ensure that the sewage plant internal chambers valves line up is correct – chamber drain valves are shut, and the sewage discharge pump suction is connected to the final stage (sterilization compartment) only.
Check aeration blower air pressure. The normal working range is 0.2-0.4 bar.

OBS # 2: Disinfectant / Sterilization tube choked.

Make sure the sterilization tube is not choked. Put only the required tablet as prescribed in manual. There should be consumption of the tablets as well as the outlet effluent should confirm the presence of residual chlorine <0.5 mg/L.

OBS # 3: Sewage three-way inlet valves (2 in no’s) found seized.

Make sure the 3-way valve are not seized and can be easily changed over. Ensure that these valves are operated fortnightly.