Wärtsilä future programme development manager Wei Chen explains why corrective action is required for the guidelines governing sewage treatment plant effluent standards
IMO’s Marpol Annex IV Convention, which was developed in the 1970s and ratified in 2003, targets the ‘Prevention of pollution by sewage from ships’. For good reasons, installing an approved sewage treatment plant (STP) has become a popular option for ships sailing internationally. The Marine Environmental Protection Committee (MEPC) has developed guidelines on STP effluent standards and performance test specifications. However, in the absence of an effective enforcement regime, the vast majority of STPs installed are discharging virtually untreated sewage (MEPC 67/8/1). In some regions, marine rules are now perceived as legalising ships’ sewage pollution. Clearly, Marpol Annex IV has not been effective and the gap between the rules and reality is widening.
To make matters worse, in racing to the lowest level of functionalities and cost, some approved STPs do not conform to the established guidelines, or even to environmental science and engineering principles. Non-conformities and ‘magic boxes’ have found their way into new ships in their hundreds. The credibility of the approval regime has been undermined. In 2017, MEPC-approved amendments to the guidelines, which is scheduled for a PPR 6 meeting in early 2019.
“Non-conformities and ‘magic boxes’ have found their way into new ships in their hundreds. The credibility of the approval regime has been undermined”
With the poor performance status, non-conformities, and magic boxes being endorsed and approved under the current regulatory framework, being compliant no longer means being green.
Visibility is key
It is rare to see an international environmental regulation fail an entire industrial sector so dramatically. The situation is particularly at odds with the tangible improvements made to our aqua environment by the land-based wastewater industry, where effective enforcement regimes exist.
Alaskan waters have a local compliance program in place for large cruise ships. The cruise industry has been successful in developing Advance Wastewater Treatment Systems (AWTS) that perform with good compliance. An AWTS carries the same certificate as an STP, but has significantly higher capex and opex numbers. Is an AWTS the right answer for other shipping sectors? No one knows.
We do know that the existing effluent standards are, at best, aspirational, judging by the poor performance status of approved STPs. Without an enforcement regime in place, no one knows the limits of available technologies, or whether existing effluent standards are evidence-based, practicable and sustainable.
Performance status of approved STPs (credit: Wärtsilä)
Without these much-needed visibilities, efforts to improve the guideline may be in vain. A relevant example is the so-called ‘dilution compensation factor Qi/Qe’, which is the single new criterion introduced in the current MEPC.227(64) guidelines that came into force in 2016. The aim was to combat STPs which use large amounts of sea water to keep the effluent ‘clean’. Two years on, none of these STPs has provided any evidence of the Qi/Qe, rendering this new introduction meaningless. Dilution machines continue to thrive.
At a time when widespread non-conformities are approved, making the performance status of STPs visible will help in finding a constructive and effective way forward. Online monitoring has proven to be effective in upholding technological thresholds under other marine environmental rules.
Guidelines are meaningful only when they are conformed to. Corrective actions are essential against the non-conformities already approved by member states. The existing guidelines can be amended in a constructive way to tackle non-conformities, as well as to improve STP performance status. STP performance tests may continue to play a key role in combatting dilution machines and magic boxes, aided by the possible introduction of online monitoring under the new guidelines. Making the performance status of STPs visible is a first step towards a future regulatory framework that is evidence-based, practical and sustainable. But ultimately, only effective enforcement can make it possible for the industry to proudly fulfil the environmental obligation of Marpol Annex IV. And only the collective efforts of the member states can make it a win-win for all.