Fifty years ago, most Coastsiders dumped raw sewage into the ocean along with phosphate, chemicals, rags, and grease. What a horrid legacy! Then came the Sewer Authority Mid-Coastside in the 1970s.

Recently, Kishen Prathivadi, SAM’s general manager, was kind to give me a walking tour of the facility. I want to share with you what he and his team have accomplished and where it can go with our support.

We no longer dump raw sewage into the ocean. Instead, when you flush, an elaborate mechanical system collects, stores, treats and discharges treated water to the ocean. It’s mostly automated with very large pumps, filters, aerators, collectors, tanks and generators. Each of these are massive to handle an average of 1.5 million gallons a day. So, when you throw chemicals, rags and grease into the toilet, most, but not all, are automatically separated. Rags are particularly tough on equipment. That’s where it can break down requiring a personal touch.

It takes dedication to run such a vital utility. We tend to think things disappear when flushed down the toilet, but it’s possible to trace almost everything back to the source. So that monogrammed hanky might one day be returned to you with a fine.

It might seem annoying but if you had a septic tank or compost toilet you’d quickly get accustomed to paying close attention to what goes into it. Egg shells, grease and chemicals destroy the microbiological community that decomposes waste. Too much and you would face an expensive fix. Whether a sewer treatment center or a septic tank, that tiny community of organisms works its magic. A large part of the maintenance cost is attributable to keeping that biological process alive.

This symbiosis is also true for our commercial partners on the Coastside. Making wine and beer is a great service for locals and visitors alike, but imagine the outcry if they dumped the waste product on the public road for someone else to clean up. Most products have waste that can be recycled. Wine and beer use a lot of yeast, hops and grapes. The residue can be recycled, but if discarded into the sewer, it must be biochemically treated just like raw waste. It requires oxygen in the treatment tanks and is measured by an analysis of biochemical oxygen demand. There are legal limits of BOD because managing it is at the heart of sewer treatment design and operating costs. Some abuse the legal limits on BOD. Like residential sewer waste, commercial waste leaves a fingerprint and can be identified with attributed costs.

We all pay little attention to our sewer treatment. Out of sight, out of mind. But, in fact, without a treatment plant, very few could live along the Coastside since decentralized treatment is inadequate and expensive for our many small lots and thin soils. Yet the cost of our sewer treatment is a fraction of what most pay for electricity or water.

Like for electricity and water, sustainability is important, and SAM is headed in that direction, but too slowly. Needed upgrades have been deferred. For example, recycling water at the treatment plant has been designed over 10 years ago. Sewage can be nearly 100 percent recycled with existing technology and existing uses. Sewage is mostly water, fertilizer and some unusable junk. Today, our treatment center throws away the water and fertilizer into the ocean but curiously saves our junk in a landfill. With tertiary treatment, water can be recycled for irrigation. Also, most of the solids can be processed into usable fertilizer. SAM’s foresighted planners have already designed the upgrades. The solid fertilizers can be extracted and used for growing some agricultural products.

Imagine a future, upgraded SAM producing 1.5 million gallons of recycled water every day. That’s enough for road median vegetation, greenhouses, specialty farms and recreational open spaces. We collectively use at least that much water for irrigation, but it's treated to drinking water standards. Tertiary treatment is required to recycle water for irrigation, but that is already on SAM’s planning horizon anyway, due to regulations.

A future of sustainable sewer treatment solves not just our sewer issues but also our need to conserve water while keeping our Coastside an enjoyable destination for residents and tourists alike.

Bill Balson is a retired engineer and economist who lives in Half Moon Bay.

Recommended for you

(2) comments

Jim Larimer

Bill Balson has raised an important issue for our community. Recycled water would make our community drought tolerant for the foreseeable future. Climate change has reduced the availability of water regionally making droughts a growing peril for our community. Our sewage treatment plant is at the end of its service life. The convergence of these two forces has given us an opportunity to create a sustainable and reliable water supply out of water that would otherwise go directly into the ocean.


1. Anti-biotics will also kill the microbes that keep your septic system working.

2. A firm named Synagro takes the solidified sludge and can use it for growing crops for livestock. Not sure if SAM sludge is high enough grade; Pacifica's is, and they do this.

3. The 3 SAM partners spent just over half a million dollars to complete feasibility analysis for recycled water. It was completed in the middle of 2017, two weeks before HMB sued its partners....

Welcome to the discussion.

Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.
Don't Threaten. Threats of harming another person will not be tolerated.
Be Truthful. Don't knowingly lie about anyone or anything.
Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.
Be Proactive. Use the 'Report' link on each comment to let us know of abusive posts.
Share with Us. We'd love to hear eyewitness accounts, the history behind an article.

More Stories