Page 45: of Maritime Reporter Magazine (January 2022)

TECH FEATURE WASTE WATER © bortnikau/AdobeStock

Source: Wartsila Water Systems Ltd.

inclusion of grey water, and the fee systems, etc. The emerg- necessity for having an effective MARPOL Annex IV [20]. ing aspirations to receive sewage from cargo ships [20] may Not all WWTWs remove nutrients. Those WWTWs serving spread the uncertainty of PRF adequacy to smaller and more <10,000 p.e. are not required to remove TN. They become a remote ports that are served by smaller WWTWs. But PRF nutrient leakage when receiving ship sewage. Larger WWTWs adequacy is not all. can be overloaded by ship sewage during peak loading condi-

Maximum permissible sewage concentrations. Wastewater tions especially in the absence of storage tanks in PRFs [5]. entering local sewers can be restricted by maximum permissi- Crucially, the timing, quantity, or quality of ship sewage are not ble concentration limits to protect the local infrastructures from visible to the receiving WWTWs. The disposal route of road corrosion, odour, toxicity, health&safety risks, and to safeguard tankers and barges may not be traceable. This lack of transpar- the compliant performance of local WWTWs. Ship sewage ancy undermines the extended producer responsibilities (EPR) readily exceeds these limits by a long way (see table), not to and risks potential nutrient leakages from facilities ashore. mention sewage sludge. The situation can be alleviated when Should a passenger ship rely on PRF or STP? Many ship ship grey water is one day regulated together with sewage – a owners choose to install STPs to gain ? exibility and green www.marinelink.com 45

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