A Good Operator Can Carry a Plant. He Cannot Carry a Bad Design.

Every few months I get the same phone call. The plant was fine. Nobody changed anything. And now the water going out of the final tank is grey, the aeration tank smells sour, and the client wants to know what happened to the system we built.

Then I ask one question: is it still the same operator?

Often it is not. He resigned, or he was moved to another department, or the maintenance contract was given to somebody cheaper. The plant did not fail. The person who was quietly holding it together stopped coming to work.

I want to write about that person honestly, because I think our industry talks about operators in two wrong ways. Either we pretend the operator does not matter, and we sell “fully automatic” plants that supposedly run themselves. Or we blame him for everything, which is what usually happens when an undersized plant fails and somebody needs to be at fault.

Neither is true. Here is what I have actually seen after years of commissioning and rescuing sewage treatment plants around the Philippines.

What a good operator is really doing

A biological sewage treatment plant is a farm. You are growing bacteria, and the effluent quality is just the by-product of whether those bacteria are healthy. Bacteria do not read the operation manual. They respond to what is happening today: how much load came in, how much oxygen they got, how long they stayed in the tank, whether somebody dumped bleach down a floor drain at 2am.

A good operator is the only person in the building who notices those things.

The best operator I ever worked with ran a plant at a hotel property. He was not an engineer. He had a one-litre plastic cone, a notebook, and a habit. Every morning at the same hour he drew a sample from the aeration tank, filled the cone, and wrote down where the sludge had settled after thirty minutes. That is all. No lab, no meters he could not afford.

But because he did it every single day, he could tell me things the lab report could not. He knew that his sludge normally settled to a certain line, and that when it started settling much faster and the water above it turned clear but slightly yellow, he was losing his population and needed to slow down his wasting. He knew that when it refused to settle at all and stayed fluffy, something had come into the plant from the kitchen side. He caught problems four or five days before they would have shown up in a discharge monitoring report.

He was not doing chemistry. He was doing attention. That is the real skill, and it is rarer than any certificate. The same is true of what a plant smells like — it is free information that most people walk straight past.

The plants that give me the least trouble are almost never the ones with the most instrumentation. They are the ones where somebody walks the plant daily, listens to the blower, looks at the foam, smells the tank, and writes it down. A logbook with six months of boring entries is worth more than a control panel full of lights.

Now the part nobody wants to hear

A good operator can carry a plant that is slightly wrong. He cannot carry a plant that is fundamentally wrong, and it is unfair of us as designers and contractors to expect him to.

I have walked into plants where the operator was being scolded in front of me, and within twenty minutes it was obvious the man had been doing an excellent job of losing an unwinnable fight. The aeration tank was sized for a building occupancy that had been exceeded two years earlier. There was no equalisation, so the whole day’s flow arrived in three hours in the morning and three hours in the evening, and during those hours the sludge simply washed over into the clarifier. He had been manually adjusting return sludge twice a day to compensate. He had been running blowers longer than he should, and eating the electricity cost, to keep dissolved oxygen from collapsing at peak.

He was compensating for a design decision made before he was hired. No amount of daily discipline fixes a tank that is too small. You cannot operate your way out of insufficient volume, and you cannot operate your way out of a plant with no buffer against shock loads. This is worst on small plants, where there is no dilution to hide behind.

So when a plant fails, the first honest question is not “who is operating this?” It is “what is this plant being asked to do that it was never built to do?”

The design test I now apply to my own work

This is the part that changed how I design.

If a plant only performs when a skilled, motivated operator is watching it closely, then the plant has a design problem that we are hiding behind a person. And people leave. They get better offers, they get sick, they get reassigned, they retire. The design must survive that.

So when I look at my own drawings now, I ask whether the plant can absorb an ordinary bad week. Can it take a Sunday when the function hall is full and the flow doubles? Can it survive two weeks of an operator who is competent but not exceptional? Can it survive a month where nobody wastes sludge because the vacuum truck could not get scheduled?

That is why I would rather give a client more aeration volume than the calculation strictly requires, and why I like fixed-film media in the aeration tank. FBBR-style fixed-film media holds a resident population of bacteria on the media surface that does not wash out with the mixed liquor. When the plant gets hit — a shock load, a bad settling week, an operator who over-wasted — that attached population is still there when the storm passes, and the plant recovers in days instead of restarting from nothing.

It costs more up front. It also means the difference between an excellent operator and an average one becomes a matter of efficiency rather than a matter of compliance. That is a much healthier position for a client to be in. This is how we approach a new plant.

The same thinking applies to how much automation I recommend. Automation is good at doing a fixed thing reliably. It is very bad at noticing that something is wrong. A timer will run a blower on schedule whether the bacteria need oxygen or not. Automation reduces the labour of operation. It does not reduce the need for judgment, and any of the wastewater companies in the Philippines that sell you a plant on the promise that it needs nobody are selling you a future problem.

What to do if your operator just resigned

If you are a facility manager reading this and your operator is leaving, the handover is the single most valuable thing you will get from him, and most companies never ask for it.

Before he goes, sit with him for one hour with the logbook open and get him to tell you what normal looks like on your specific plant. Not the manual’s normal — yours. What the settled sludge level usually is. What the tank normally smells like. Which valve position the return sludge is usually left at. Which hour of the day the flow peaks. What he does differently when the building is full. Which alarms have been ignored for a year and why. Record it on your phone if you have to.

Then give the new person thirty minutes a day and a notebook, and do not judge his work for the first month. He is building the same instinct the last man had, and there is no shortcut to it. If there is a gap between the two of them, we can cover the plant while you hire.

And if you have already gone through two or three operators and the plant keeps degrading each time, stop looking for a better operator. That pattern almost always means the plant is running with no margin, and every new person is being handed a system that only works if it is nursed. That is not a hiring problem. That is an engineering problem, and it is usually fixable without rebuilding the whole plant.

Where I land on it

I have a lot of respect for good plant operators. They are usually the lowest paid person involved in a project and the reason it passes its permits. When I commission a plant, the operator is the person I want in the room, because he is the one who will still be there long after we have demobilised.

But I do not want to design plants that need him to be exceptional. My job is to build something an ordinary careful person can run on an ordinary busy week, and that gives an exceptional person room to make it excellent. If the plant needs a hero, I did not finish my work.

If your plant has been through several operators and keeps drifting out of compliance, or you are about to lose the person who knows your system best, book a free 15-minute consultation with us. Tell me what your plant does on a bad week, and I will tell you honestly whether you have an operator problem or a design problem.