Let It Flow

By Nick Schou   |   February 13, 2020
The Montecito Sanitary District

The Montecito Sanitary District (MSD) was formed in 1947 with the sole purpose of collecting, treating and disposing of the community’s wastewater, but it didn’t actually come online as a completed sewage system and treatment facility until the early 1960s. Today, the MSD serves approximately 3,100 customers in Montecito, with only a scattered number of parcels still using their own septic systems. With a total of 76 miles of sewer lines, the system pumps approximately 550,000 gallons of waste per day, all of which ends up at the MSD’s treatment center at the end of a private road just south of the 101 Freeway.

Earlier this week, I took a tour of the facility, along with Woody Barrett, one of MSD’s governing board of directors, and Alex Alonzo, the plant’s operations manager. Guiding the tour was Marc Ciarlo, a Grade 5 Operator, the highest level attainable in the state of California, and Daniel Jacquez, the chief plant operator. My visit began where everything that is flushed down the drain in Montecito ultimately ends up, at MSD’s inflow pump station.

After descending two steep staircases – the pipe brings sewage into the facility a full two stories underground – we enter a small, slightly foul-smelling concrete chamber and gather over a steel grate. Several feet below us is a swift-moving river of raw sewage that has just arrived. Before the water is pumped upstairs into the treatment area, it must first pass through a channel grinder, a pair of motor-driven rotary cylinders with teeth that rip apart any trash or debris entering the facility.

Raw sewage entering the Montecito Sanitary District, two stories underground

Because Montecito only has a few restaurants and hotels feeding into the pipes – Coast Village Road, being part of Santa Barbara, isn’t part of the system – MSD doesn’t get the same variety of waste that most cities need to treat. That said, because of Montecito’s semi-rural nature, there are always unwanted travelers in the pipes. A rake propped up in the corner is used to pluck out stubborn pieces of non-organic material.

 “Large pieces of debris impact the performance of the pumps,” Ciarlo tells me. “Sometimes we get flushable wipes,” which gum up the works, he adds. “Don’t flush those.”

Unsurprisingly, MSD’s treatment facility operates on a diurnal schedule. During the night, when most people are asleep, the flow into the plant trickles to a stop. But by mid-morning, the flow begins its inexorable rise to a steady peak volume that lasts throughout the day and evening. There are instruments to measure the rise in flow, Ciarlo says. “If it’s an inch above the target set point, it sends a message for the motor to speed up.”

A backup generator is in place to keep the plant running in the event of a power loss, which if not swiftly resolved, would lead to a sewage spill. The last time this happened was during the January 9, 2018 debris flow event. “During the debris flow, when the water turned off, it flipped over automatically,” Ciarlo says. “We do a load transfer test every month and it’s incredibly reliable. If the power goes off for days, it’ll run for days.”

Microorganism Warfare

Separating solids from water, one step at a time

After being pumped upstairs from the inflow pump station, Montecito’s wastewater flows to a pair of swimming pool-size aeration basins, each 17 feet deep. “This is our suspended growth activation sludge system,” Ciarlo tells me. “We have a microbial community colony; about 15000 pounds of microorganisms are what are being used to decompose and degrade the organic matter coming into the treatment zone.”

In other words, according to Ciarlo, all the bugs that help break down the sewage originated in our collective stomachs. “If you think of your own gut, the bugs are right there,” he explains. “The gut microbiome is dependent on your diet, so the colony of microorganisms we have are there because of the diet of wastewater food coming into the plant. It’s biomimicry: We have engineered a system that’s mimicking what the human body does.”

The two aeration tanks before us are being injected with a constant, high-pressure supply of air via fine bubble diffusers which cause the earthy brown surface of the two pools to churn with turbulence. At 370,000 gallons each, the tanks hold a total of 740,000 gallons of water for anywhere from six to 18 hours, depending on the flow. The supply of oxygen allows the microorganisms to live, consume and reproduce. Amazingly, even while standing just a few feet away from the frothing liquid, there is no noticeable odor.

“The water isn’t brown because of fecal matter,” Ciarlo insists. “It’s because of all the microorganisms in there. If you took a small handful of soil, you have millions of microorganisms right there, so think of that in terms of all that brown water; it’s just microorganisms breaking down and speeding up the decomposing process.”

Mixed Liquor

Scrapers salvage solid waste material

After being aerated, the water is pumped into two secondary clarifier tanks, where it turns into what sanitation industry people refer to as “mixed liquor.” The term refers to the visibly bifurcated nature of the liquid waste: clear on top and dark on the bottom, like a cocktail. The two-tone appearance comes courtesy of gravity. All the solid organisms, which will eventually become recyclable sludge usable for fertilizer, quickly sinks and settles at the bottom. Meanwhile the clear water filters through a series of weirs before being blasted with industrial strength bleach and dechlorinated with sodium bisulfate and finally emptied into the ocean.

Currently, MSD does not recycle its clean water, which is pumped into the Pacific Ocean at a depth of 40 feet some 1600 feet offshore from Butterfly Beach. (With help from an Israeli firm, MSD has a pilot project underway to recycle water and hopes to provide up to 60,000 gallons per day of it to customers including the nearby Santa Barbara Cemetery.)

Long after the purified water is pumped into the ocean, the solid waste that has been collected in the clarifier tanks remains onsite, where it is subjected to what can perhaps best be described as microscopic warfare. “The microorganisms coming into the plant multiply and make more organisms,” Ciarlo says. “To operate this plant we need to maintain a target biomass population. So in order to do that we have to offset the new growth by eliminating some of that activated sludge.”

This task is accomplished via an aerobic digester, which helps thicken the sludge into a bubbly stew like chocolate pudding being mixed in a blender. “The food source here is the waste sludge,” Ciarlo continues. “The microorganisms in this tank are surviving by eating other microorganisms. So we are getting some volume reduction and also getting pathogen destruction.”

High Quality Sludge

Solid waste makes its final lap towards the dumpster

The Montecito Sanitary District employees 17 full-time people, including Carole Rollins, a laboratory manager and four maintenance workers who constantly survey the underground lines that lace the hills above MSD’s treatment plant. “We’re accredited through the state of California,” Rollins observes. “They keep an eye on us and inspect us. We submit data to the state.”

On the wall of the laboratory is a poster showing the microscopic profiles of all the microorganisms whose numbers need to be measured by MSD, which submits data to the state on a regular basis. Ciarlo points to a bubbling flask of liquid on the countertop; it is wastewater being injected with oxygen, thus mimicking the aeration process. After removing the air supply, the mixture vertically separates into clear liquid and solid waste. “Our duty as operators,” Ciarlo argues, “is to get the highest quality sludge.”

The length of time that solid waste spends at MSD’s treatment plant is referred to as an SRT, or Solids Residence Time. “The biomass resides from anywhere from fourteen to twenty days before it makes its way to solids removal,” says Ciarlo. By comparison, water leaves the plant and enters the ocean 10 to 20 hours after arrival, depending on demand.

The final step in the solid waste disposal process is a belt filter press. “We use polymer as a coagulant to fuse the particles together,” Ciarlo says. “It’s a compression process where the water is squeezed, and the solids are concentrated and trapped on the belt and the scrapers take the solid waste on to the conveyer belt and into the dumpsters.”

Harvest Blend

After my tour, I sit down with the Montecito Sanitary District’s general manager, Diane Gabriel, who serves on behalf of the five member board. Gabriel starts off by telling me that, unlike other utilities, MSD doesn’t charge a monthly bill for its services. Rather, per Proposition 13, each property owner in town must pay one half of one percent of their property taxes to fund the agency.

“We have to charge for our service,” Gabriel points out, adding that the revenue has funded the agency’s recycled water initiative; MSD has set aside $1.1 million over the next two years to fund the project. “The funds are coming from everybody and recycled water is to the benefit of everyone in the community, especially when it comes to drought-proofing,” Gabriel says. “Now we are able to look at recycling at a much larger scale.”

A “Complicated yet Simple” operation

Outside, at the far end of MSD’s treatment facility, two conveyor belts deposit solid sludge into a pair of rolling container-size industrial dumpsters. “They bring us two empty bins and take the full bins away,” Gabriel says. “We are paying them for the trucking, but they are performing more treatment on the waste, composting it.”

Engel & Gray, the contractor that picks up the dumpsters, transports the waste to Santa Maria, where it is mixed with various other waste products and transformed into Class A fertilizer sold at locations such as Home Depot under the brand name Harvest Blend.

“It would be virtually impossible for us to become a composting facility,” Gabriel adds. “You need to have that out in ‘ag’ land, [where] they are bringing in vineyard waste and chicken poop and garden waste and they turn it into a nice product called “Harvest Blend Compost,” which you can buy at Home Depot. We are fortunate to have operators who know the math, but also – since it’s more than science – know the art.”


You might also be interested in...