Biological Sewage Treatment for Marine Applications

The new Evac EcoTreat biological wastewater treatment plant is claimed to deliver the best of both worlds for owners of small vessels, with cost-effective treatment of black and gray water that meets and exceeds the latest environmental standards.

Available in capacities from 2–11 m3/day, the plant is compatible with both gravity and vacuum-based wastewater collection systems.

It is a 100% biological system for the efficient treatment of black wastewater from toilets and urinals and gray wastewater from washbasins, sinks, and showers. Evac says that treating waste water in this way completely eliminates the need for any chemicals, filters, or membranes.

The plant has been designed to make operation and maintenance as easy and cost effective as possible, while its compact footprint and low weight is said to make it suitable for smaller vessels where space restrictions may be tight.

OPERATING PRINCIPLE
Evac EcoTreat uses the submerged fixed-film bacteria principle. Black and gray water waste streams are fed to the inlet mixing tank either by gravity or by a vacuum pump. From there, the wastewater is transferred to the bioreactor tank by a macerating pump, which mixes gray and black water and cuts up solids.

The wastewater is then driven through the matrix in the bioreactor tank by compressed air that is supplied by diffusers in the bottom of the tank. The air supplies oxygen and also enhances the biological process.

The treated water flows from the bioreactor tank into the settling tank by gravity, where it passes through the settling matrix. Before being transferred to the clean water tank, the water is exposed to an advanced UV light filter to eradicate all heat-resistant coli bacteria. Any organic or mineral sludge that accumulates in the settling tank is transferred back to the bioreactor tank for further treatment or removal from the system.

Evac EcoTreat is type approved and wheel-mark certified by DNV in accordance with IMO MEPC 227(64). Furthermore, the plant is also approved by the U.S. Coastguard and Transport Canada.

Mats Riska, Product Manager, Wastewater Treatment Systems at Evac said: “This new solution together with our existing advanced wastewater treatment solutions such as Evac EcoOcean MBBR (moving bed biofilm reactor) and Evac MBR (membrane bioreactor) means we can address the various needs of all our customers in the marine sector.” 

Source: Maritime Journal