"Sir, Would You Drink It?" My Honest Answer About Treated Wastewater

The water news in Cebu has been the same story all year. The district has been managing a supply gap for months, the city has gone back to the idea of drilling wells in public schools, and every barangay has its own version of the schedule when water comes and when it does not.

So the question I get on site visits now comes faster than it used to. We are standing at the discharge point of a sewage treatment plant, the client is watching clear water come out of the final tank, and somebody says it:

"Sir, would you drink it?"

For years I gave the clever answer. These days I give the honest one, because the honest one is more useful to the person asking.

Yes, it can be done. No, not by this plant.

Treated wastewater can absolutely be made safe to drink. Singapore does it. Windhoek in Namibia has been doing it since the 1960s. Parts of California do it. The technology is real and it is not a secret.

But those are not sewage treatment plants. They are drinking water factories that happen to use sewage as their raw water, and they are designed, staffed and monitored as drinking water factories from day one.

The plant we are standing in front of was designed to a different brief. It was designed to meet DENR DAO 2016-08 discharge limits for the class of the receiving water. BOD, COD, TSS, ammonia, phosphate, oil and grease, coliform, all brought down to numbers that will not harm the creek or the sea it goes into. That is the job it was given and that is the job it does. Nobody asked it to produce water that goes inside a human being, and nobody paid for it either.

What a discharge test does not ask

The lab report the client is holding looks impressive. It is also answering a completely different question from the one the drinking water standard asks.

A discharge test tells us whether the water will damage the environment. The Philippine National Standards for Drinking Water asks whether the water will damage a person. Those are not the same list. Drinking water standards chase heavy metals, disinfection by-products, dissolved solids, and pathogens at a level a discharge test never goes looking for. Chlorine at the dose we use at the end of an STP will handle bacteria. It does not deal with viruses and it does not deal with protozoa like Giardia and Cryptosporidium, which are the organisms that actually put people in hospital.

Then there is timing. A discharge sample is a snapshot, taken once a month or once a quarter, and the result comes back days later. Drinking water needs to be watched continuously, with instruments that can stop the water automatically the moment something reads wrong. A bad day at a sewage treatment plant means a bad lab result and an uncomfortable phone call. A bad day at a potable reuse plant means something else entirely.

How many barriers it really takes

An example from our own work, without naming the client. We designed a treatment system for a hemodialysis centre in Metro Manila, thirty beds, about 30 cubic metres a day. The goal there was not drinking water. The goal was only to bring that effluent to the Class C discharge standard.

Even for that, the train needed ozone with venturi injection, catalytic granular carbon with manganese-impregnated media, UV, chemical phosphate removal, and forced exhaust to handle the off-gas. All of that, just to send the water to the drain with a clear conscience.

Now think about what would have to be added on top of that to make the same stream safe to drink. Membrane filtration. Reverse osmosis. A second, independent disinfection barrier. Remineralisation, because RO water is aggressive to pipes and tastes like nothing. Online instruments on every single barrier. A divert valve that automatically dumps the flow the instant a reading goes out of range. Enough redundancy that no single failure can ever reach a tap. And a trained operator who is actually there.

Here is the part that surprises owners. The treatment equipment is the cheap half. The monitoring, the redundancy and the operator competence are the expensive half, and unlike the equipment they are expensive every month, forever.

My worry is never the good day

Nobody should judge a plant by the day the sampling team visits. Judge it by Sunday at two in the morning, when a blower trips and nobody notices until Monday.

I learned that early, on one of our first industrial jobs. It was a food processing plant, hams and hotdogs and beef jerky, and I underestimated the emulsified fats and oils in that wastewater badly. We had also allowed the domestic and process streams to be combined into one line, which pulled the whole plant under stricter parameters than it needed to be under. My first attempt at the fats was a grease interceptor when the honest answer was dissolved air flotation. The plant only settled down after we retrofitted FBBR-style fixed-film media into the aeration tank so the biology had somewhere to hold on. The whole story is written out here.

What stayed with me was not the equipment mistake. It was how easily one change upstream, in a kitchen I could not see, moved my effluent numbers. If somebody's decision at the trimming table can shift what comes out of my final tank, I am not putting that water in a glass. That is not humility, that is arithmetic.

The better question to ask

When a client asks me about drinking the effluent, what they usually mean is something more practical: is this water worth anything, or am I just paying to throw it away?

That question has a good answer. Treated effluent that is nowhere near drinking standard is still perfectly suited to toilet flushing, cooling tower make-up, landscape irrigation, floor and vehicle washing, and fire reserve. Many of those uses need only filtration and a small chlorine residual on top of what the plant already produces, and none of them involve anybody swallowing anything. In a province where the district is rationing supply, that is where the real money is, and it is a much shorter conversation than potable reuse. Whether it actually pays on your site is arithmetic worth doing first.

If a supplier tells you their plant makes drinking water

Ask them four things. What standard was the plant designed to, discharge or potable? Which instruments are online, and what happens automatically when one of them reads out of range? Who is watching the plant at two in the morning? And how many independent barriers sit between the toilet and the tap?

If the answers are vague, you are listening to a sales line, not a design.

So, would I drink it?

Standing at the discharge point, my answer is this. I am proud of that water. It is clean enough to go back to the environment without harming it, which is exactly what we designed it to do. I would wash with it, irrigate with it, flush with it, and run it through a cooling tower without hesitating.

I would not drink it. Not because the technology cannot get there, but because this plant was never asked to go there, and pretending otherwise is how people get hurt.

If you are looking at a plant right now and want a straight answer about what it can and cannot do, including whether reusing your treated water makes sense for your site, that is the kind of conversation we are happy to have before anybody talks about equipment. We are one of the few wastewater companies in the Philippines that will tell you when the answer is to do less. Book a free 15-minute consultation and bring your latest lab results.