The De Nora blog: Water Made Easy

5 Things You Need to Know About Solids in Marine Sewage Treatment

Aug 26, 2020 8:30:00 AM / by De Nora

Offshore oil and gas platform

On offshore Oil & Gas production and extraction facilities, the sewage treatment system often manages an enormous amount of raw wastewater, i.e., …human sewage. The untreatable or separated wastes from these systems are commonly referred to as “screened or filtered raw biomass”, or, “wet waste sludge.”

At De Nora, we’ve provided advanced electrolytic water treatment technology to the Oil & Gas industry for four decades. If you’re planning a marine sewage treatment system for a new-build asset (rig or platform) or upgrading your current marine sewage treatment system, here are four key things to consider in managing sewage sludge or wet waste solids. 

You can't dump suspended solids-laden waste

It’s important to understand that filtered bio-mass, sludges, or wet waste discharges from a marine sewage treatment units are not considered treated and cannot be discharged to sea per the IMO MEPC.227(64) guidelines. As conventional treatment methods do not easily destroy much of this solids matter, the handling of these wet wastes must be managed separately from the sewage treatment unit itself.

A centrifuge IS better than a sludge tank

Without a centrifuge or other wet waste handling unit, waste sludges must be collected in a sludge tank and subsequently sent ashore for further treatment at a municipal wastewater treatment plant. This approach not only requires more handling logistics and expense; it requires more space onboard — and space is a premium on offshore production and extraction facilities.

One side does NOT fit all

Knowing the daily volume of wet solids produced and the required holding duration is essential, as this directly relates to the size of the sludge tank that your installation will need. For larger systems (24 cubic meters per day and above), De Nora strongly recommends its centrifuge-based solids-handling system. This approach reduces the logistical cost of sludge tank management and offloading wet sludge from your installation and produces a more sanitary, non-hazardous, dewatered product for transportation to shore that is Class ‘B’ compliant for landfill – no further municipal treatment is required.

Everyone wants to take a "hands-off" approach to solids handling

A system such as our OMNIPURE™ SHS (solids handling system) allows for hands-off operation during solids dewatering and requires minimal effort to change out the dewatered solids container when full. The 10-13% dewatered material is the consistency of damp mud or potting soil and dries rapidly due to its low moisture level. The dewatered solids delivered from the unit meet the Class-B rated sludge material parameters and is non-hazardous and can be combined with the rig’s other domestic trash for traditional landfill disposal

Think inside the box or barrel

It’s essential to consider the logistics of handling your domestic waste or trash and incorporate the desired type of refuse collection container into your waste handling process for hassle-free transportation of the dewatered wastes to shore. Disposable container options such as barrels or lined corrugated totes can simplify disposal at an onshore landfill.

Want to learn more about solids handling? Download the ebook

Content for this post was excerpted from our downloadable ebook, Solids Handling for Offshore Oil & Gas. It’s free and available online at our website:

Get the EBook



Tags: De Nora, Sewage treatment, oil and gas

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