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MCBH’s Wastewater Treatment Plant

By Susan Bryan - Environmental Outreach Specialist | Marine Corps Base Hawaii | March 10, 2020


Think you deal with a lot of crap at work?  Well, urine for a surprise! 

Aren’t you even a tiny bit curious as to where your dishwater goes when it disappears down the sink in a swirling vortex?  All the sunscreen, dirt and sand you wash off your kids?  And when you flush the toilet...? 

Most of us take the “out of sight, out of mind” attitude; and as long as itgoes down the drain, some of us don’t care where it goes or what happens at the Wastewater Treatment Plant (WWTP).  But the staff of the WWTP are hoping we’ll become more aware of our actions as we wash our dishes, do our laundry, and flush our toilets.  Did you even know we have an award-winning WWTP? 

Some of our uninformed and mostly unintentional actions have consequences—someone is left holding the proverbial pot!  And, cleaning that pot is costly.  However, if we understand the process, things can flow more smoothly and folks at the WWTP will be relieved. All jokes aside, our Waste Water Treatment Plant, also known as the Water Reclamation Facility (WRF), is vital to the environment and public health.

The scoop on poop and other items that make their way to the WWTP:

Omitting the unpleasant details, Preliminary Treatment of the debris from the swirling vortex occurs at the entrance or “head-works” of the facility.  It involves removing the floating stuff like leaves, feminine hygiene products, “flushable” wipes, and inorganic solids such as sand and dirt.  At MCBH, the process of screening is accomplished with the use of a combination of mechanically cleaned bar racks and a hand cleanable screen as back up (in case the mechanical feature breaks down—it’s a dirty job).  Sewage passes through a ‘fixed’ screen consisting of slots to remove coarse solids such as leaves, paper, plastics, etc.  The heavy inorganic materials such as grit, sand and gravel settle to the bottom of the grit chamber with assistance from gravity. The sewage is reaerated at this stage to keep it from going septic—no bad odors = winning!

In addition, there’s an odor control operation that uses an enclosed biological filter unit to help remove hydrogen sulfide and other odorous compounds. Smell ya later!  Seriously, the MCBH operation doesn’t smell like other nearby treatment facilities. It resembles a bird sanctuary with a waste water treatment plant on site. Removing odor-causing chemicals also helps to reduce corrosion of the electrical components at the facility, saving big bucks and smelling nice—success!

Getting down and dirty:

Secondary Treatment is biological in nature and accomplished by magnificent microbes—beneficial bacteria.  Biological treatment of our sewage occurs in a trickling filter where microorganisms such as bacteria, algae, and fungi help to process our sewage.  The microorganisms literally consume the soluble and suspended organic matter in our sewage. The microorganisms are crucial to the wastewater treatment system, and they’re given a constant supply of oxygen to keep them happy and healthy.  High doses of chemicals and other toxic substances dumped into the sewer drains can adversely affect the delicate microbes, so never dispose of chemicals in your sink or toilet.

At the MCBH WWTP, secondarily treated wastewater goes through a polishing pond system where the microorganisms “polish off” their organic meal.  Additional time in these polishing ponds allows for further removal of organics, settling of suspended solids, and a certain degree of natural disinfection.

Technology is available to remove nutrients such as nitrogen and phosphorus from the wastewater; however, the costs associated with those processes are excessive.  In most cases, the amount of nutrients being discharged in storm water runoff are equal or greater than wastewater. Therefore, it is not cost effective to invest in higher levels of wastewater treatment in geographical areas such as Hawai’i. On the other hand, in areas where clean water is in short supply, advanced secondary and even tertiary treatment is necessary. 

After the polishing ponds, treatment is complete. The effluent from MCBH is combined with that from the Kailua Regional Wastewater Treatment Plant and discharged about a mile offshore of Kailua Bay at 110 feet below the surface of the ocean into the natural zone of mixing.  Because the effluent is mixed in a deep ocean outfall, there is no requirement for chemical disinfection. Typically, a portion of treated effluent is recycled—designated for reuse (R2 water) and is chemically disinfected prior to irrigation of the MCBH golf course. Currently, the use of R2 water is suspended pending repairs to the irrigation system and modifications to landscaping on the greens. 

Flushable Wipes Clog the System

When materials in the downward swirling vortex leave your home, they travel by gravity through a series of pipes and lift stations until they reach the WWTP. Butt—materials such as “flushable wipes” must be manually removed and disposed of at lift stations because they literally constipate the system.  This occurs because they combine with grease as they make their way through the pipes and create large “fatbergs” of flushed trash.  In other words, “flushable wipes” are not flushable!  The State of Hawaiʻi recently revived a campaign to discourage citizens from flushing wipes.  You may have seen the commercials stating, “Don’t wipe out our islands.”  The commercial shows a very graphic video of sanitation staff removing a clog of wipes from the system.  To be honest, your darling derriere-wipes are a disgusting nightmare!  Dispose of wipes, diapers, and feminine hygiene products only in the trash. Just because you can flush them doesn’t mean you should. For a ghastly and informative local news article visit:

The Golden Nugget

To put our WWTP in perspective: the MCBH facility was designed for a capacity of 2 Million Gallons per Day (MGD) average daily flow, and we generally operate at or below 1.5 MGD. Can you imagine that?

Our Waste Water Treatment Plant’s mission is to prevent, reduce, and eliminate pollution of our local waters, in compliance with the provisions of the Clean Water Act, and to reuse as much water as possible.  At the MCBH Environmental Compliance and Protection Division, we hope to develop a well-informed community aboard MCBH that will appreciate our mission to protection human health and the environment through one of our most valuable assets—the wastewater treatment facility—that is often taken for granted.  Please promote water conservation and reuse to preserve our precious natural resources. Here’s a few suggestions to start:

  • Avoid flushing “flushable” wipes, especially baby wipes. 
  • If you wouldn’t eat it, don’t put it down a drain.  Household chemicals and other toxic substances such as motor oil can kill the delicate microbes if dumped down our drains.
  • Turn it off!  Don’t let the water run while brushing your teeth or washing dishes.
  • Report leaks no matter how small.
  • Don’t take Wastewater Treatment services for granted.
  • Take a tour of the Wastewater Treatment Plant.  Due to strict policies and procedures, it’s a pleasant educational experience in a beautiful location.

For more information or to request a tour of our Waste Water Treatment Facility, contact the Base Environmental Division at 808-257-3694.

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