Ammonia Removal for Sewage Treatment Plants
Your STP is failing ammonia. It is usually fixable.
High NH₃-N on your effluent test almost never means the plant has to be replaced. In most Philippine sewage treatment plants we inspect, ammonia failure comes down to three or four correctable causes — and the fix costs a fraction of a new system.
Does This Sound Familiar
Signs your plant cannot nitrify
- Your laboratory result shows ammonia above the limit while BOD and COD pass comfortably.
- You received a notice of violation or your discharge permit renewal is being held up.
- The plant passed when it was new, and drifted out of compliance over months.
- Ammonia results swing — one test passes, the next fails, with no obvious change.
- Your building admin or the LGU is asking questions and you have no clear answer.
The Engineering
Why ammonia fails when everything else passes
The bacteria that remove BOD and the bacteria that remove ammonia are not the same organisms. BOD removers are fast-growing and forgiving. Nitrifiers — the ones that convert ammonia — are slow-growing, sensitive, and easily washed out of a system. They need more oxygen, more time, and somewhere to hold on.
That is why a plant can look perfectly healthy on BOD and still fail ammonia. The common causes we find on site:
No dedicated nitrification stage
A single aeration tank doing both jobs favours the fast-growing bacteria. The nitrifiers never get established.
Not enough air
Nitrification consumes far more oxygen per kilogram than BOD removal. Undersized or worn blowers and clogged diffusers quietly starve the process.
Biomass washing out
Suspended-growth systems lose their slow-growing nitrifiers to the clarifier. Without a surface for the bacteria to hold, the population never builds.
Too little retention time
Flow arrives faster than the biology can work — common where an equalisation tank is undersized or a facility runs only 8 to 12 hours a day.
Unreliable sequencing
In batch systems, timers, decanting and cycle faults mean the aeration phase is not actually delivering what the design assumed.
A biology that never started
Plants commissioned without proper biological start-up can run for months with a population that was never fully seeded.
The Fix
How we correct ammonia failure
1. Diagnose before quoting
We check dissolved oxygen, blower and diffuser condition, tank volumes, sludge condition and actual flow — not just the lab sheet. The lab result tells you there is a problem; the site tells you which one.
2. Stage the aeration
Separate the BOD stage from the nitrification stage. Staging diversifies the bacteria and is what turns ammonia removal from intermittent into reliable.
3. Add fixed-film media
FBBR-style fixed-film media gives the nitrifiers a permanent surface so they stop washing out. It retrofits into existing tanks — including tanks already built — and does not clog pumps or strainers the way loose media can.
4. Correct the air
Where blower capacity or diffuser condition is the limit, we size and specify what the process actually needs rather than guessing from the nameplate.
5. Rebuild the biology
Locally produced Active Cells probiotics, formulated for tropical conditions, shorten the time it takes for a nitrifying population to establish.
6. Verify with a real test
Accredited third-party effluent sampling after the correction, so you have documentation for your permit — not just our word that it worked.
Most ammonia corrections are retrofits into what you already have. We look at converting and upgrading existing tanks before we ever propose a replacement plant — including sequencing-batch systems that can be converted to continuous-flow fixed-film treatment.
Who We Are
Wastewater engineers, not resellers
Innovative Water Solutions Inc. has designed, built and rescued sewage treatment plants across the Philippines since 2013 — hospitals up to 250,000 litres per day, food manufacturing plants, hotels, condominiums and commercial buildings. We do the design, the build and the after-sales support ourselves, so when a plant misbehaves there is nobody to pass it to. See our completed projects.
Tell us what your plant is doing
Send your latest lab result and a short description. We will tell you what we think is wrong before you spend anything.