Rebuttal: Meeting IMO's Effluent Standards with Electrolytic Treatment

file photo courtesy of Diamantino Rosa
file photo courtesy of Diamantino Rosa

Published Jan 18, 2020 5:20 PM by Dana Casbeer

The Maritime Executive recently published an editorial titled Support for Major Reshape of MARPOL Annex IV.

While this is an interesting article with some notable observations, there are quite a few incorrect and misleading statements that deserve rebuttal relating to competing wastewater treatment designs such as the electrolytic sewage treatment technologies. As the true “originator” and inventor of various innovative electrolytic wastewater treatment processes for more than four decades now, the DNWT OMNIPURE™ brand of electrolytic treatment systems set the benchmark in electrolytic oxidation treatment and do not rely on mere dilution or disinfection to simply skirt the rules.

It is true that many scientific and engineering advances have been achieved in the offshore and marine wastewater treatment space, many of which are above and beyond simple biological treatment with post-chlorination. While many biological systems do perform quite well, it is not the maintenance and trouble-free panacea that many manufacturers attempt to promote into the market. There are countless numbers of biological treatment systems replaced by electrolytic treatment systems worldwide due to continual effluent non-compliance and/or arduous maintenance duties required for systems in the marine and offshore environment.

On the topic of total residual oxidants (TRO) and disinfection by-products (DBPs) generated by electrolytic treatment systems, it should be clearly understood that the use of commercially available sodium hypochlorite (liquid household bleach) NaOCl in its undiluted form of 5-10 percent hypochlorite (50,000-100,000 ppm available chlorine) can actually present a far more troubling environmental impact on the ocean environment than do the oxidants produced by quality designed electrolytic sewage treatment unit (ie…50 ppm or 0.005 wt. percent available chlorine). 

Also, such claims that the oxidants produced by electrolytic treatment systems are somehow overtly destroying the ocean environment is false and misleading, not to mention technically in error when considering the actual ppm concentrations used in the various treatment systems available on the market today.

For instance, the residual oxidant concentrations of the OMNIPURE treatment systems are far below that of liquid sodium hypochlorite that is normally added to most biological treatment systems today and is controlled specifically by the proprietary system design and DC current applied to the electrolysis process. In contrast to this, many simple biological or physical/chemical treatment systems opt to use high strength sodium hypochlorite (liquid bleach) as the final “disinfection” stage of treatment as a “belts and suspender” concept for certain shortcomings of their biological process. 

In fact, many of the latest IMO MEPC 227(64) compliant biological treatment units readily utilize commercially available liquid chlorination and a follow-up neutralization step to actually meet the IMO effluent quality standards. From the electrolytic OEM manufacturer’s standpoint, the use of high strength sodium hypochlorite, or “bulk” hypo is far more dangerous from a health and safety standpoint as well as from an environmental impact position.

As a real-world example of this, the OMNIPURE electrolytic oxidation process produces a relatively small amount of residual chlorine prior to neutralization, between 3-5 ppm, whereas many “approved” biological systems, as mentioned above, utilize commercially available high strength chlorine bleach with concentrations up to 100,000 ppm and potentially could leave a very high residual chlorine in the treated stream. Therefore, any reasonable discussions of DBPs environmental impact studies should not forgo this reality that higher concentrations of sodium hypochlorite disinfectant will be more highly reactive with the organics in the wastewater system and likely produce much higher DBPs, especially if the neutralization process of the system is not properly designed.

As OEMs of such important regulatory equipment, and if we are to be truly forward-thinking stewards of protecting our ocean environments around the world, I would not stand so high on the soapbox of persuasion trying to influence the IMO to arbitrarily denounce or condemn such proven treatment technologies as the electrolytic type. What would be a far more advantageous and suitable direction would be for the IMO to take a strong look at the numerous substandard biological system designs and eliminate the use of high concentration liquid sodium hypochlorite-based disinfection schemes from non-electrolytic type systems.

With many 1000’s of OMNIPURE electrolytic systems installed and operating globally, it is without question a well-accepted and performance-based treatment technology which has gained innovative momentum in recent years as is evident by the numerous electrolytic manufacturers entering the global marine wastewater treatment space. OMNIPURE holds various Type approvals from BV, RRS, CCS, LR, USCG, etc.

Again, I while appreciate the emphasis of this article and its focus on protecting our environment, I can’t help but remember the old proverb, “Those who live in glass houses should not throw stones.”

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.