Unfortunately, stormwater basins often go unnoticed and un-cared for. But they serve an essential role when it comes to site management. So when the pond turns green and starts to smell, it spells trouble. Not only might it mean the stormwater pond can’t perform its important job collecting runoff, it might also lead to exposure to dangerous bacteria.
Stormwater basins usually go wrong because the still water has lost its oxygen. Stormwater pond aeration is therefore usually the first sensible fix. But where should a site manager start?
Getting the equipment is the easy part. There are two much more pressing questions:
- Which system is safe near buildings and plants?
- How can you run it on a site that isn’t checked every day?
Let’s find out.
Why Stormwater Ponds Go Wrong
There are several processes that turn stormwater ponds green and smelly:
- Runoff carries nutrients into water (which barely moves)
- Fertiliser and leaf litter arrive in the first flush of a storm, along with grime washed off car parks
- They land in a shallow pond that warms quickly. Warm, still, nutrient-rich water is exactly what algae want.
- When the pond layers don’t mix, the deep water loses its oxygen to decaying leaves and dead algae. Without oxygen, the sediment gives up the phosphorus it has been holding, and that feeds the next bloom.
Owners see the damage at the surface: green water, a sulphur or musty smell, stressed fish or birdlife, and mosquito complaints. Stormwater pond aeration tackles all of these at the source, because it fixes the still, oxygen-poor water behind them.
What Retention Pond Aeration Needs to Achieve
The goal is simple: mix the water and lift the oxygen at the bottom, so the whole volume turns over at least once a day.
Retention pond aeration vs detention basin aeration
A retention pond holds a permanent pool, so retention pond aeration suits it all year. A detention basin drains between storms and may sit dry for weeks, so detention basin aeration is only really needed while the basin actually holds water. If the water doesn’t stand long enough to stratify (split into oxygen-rich and oxygen-poor layers), you probably don’t need an aerator.
Stormwater pond aeration deals with oxygen, but nutrients often need treating as well. That is where Biostim, our 100% biological probiotic, comes in. We use it at Australian Unity’s Peninsula Grange retirement living site in Mornington, which has what is technically a detention pond. It looked like a jungle swamp when we started. We maintain its existing aerator, cut back the weed and treat the algae and weeds. Biostim and Lake Bottom Blankets help keep it looking good for residents.
Choosing a Commercial Lake Aeration System
Commercial lake aeration differs from farm dam aeration in one respect: people, buildings and equipment sit close to the water. That affects which kind of aerator you choose.
Here are the options:
Subsurface diffusers
A compressor on the bank pushes air through a weighted hose to diffusers on the floor. Nothing spins or sprays, no electrics sit in the water, and the only thing visible is a patch of bubbles.
That makes subsurface aeration the safe choice for stormwater pond aeration near switchgear and plant rooms, and anywhere the public goes.
It gets more from deeper water, though, so a very shallow basin may suit a surface unit better.
Surface aerators and aerating fountains
Surface aerators are visible and work quickly, which suits shallow amenity lakes. The catch is spray. A mains Carnival throws water up to about 2 metres high and 6 metres wide. That will soak a footpath if you site it badly.
Check what you’re buying, too. Most decorative fountains don’t aerate water at all, because a genuine aerator uses a propeller. Ask what drives the unit before you accept a quote for stormwater pond aeration, and fit a guard where animals could reach it.
You should also think about what happens when the water drops. A subsurface compressor sits on the bank, so it copes. A surface unit’s submersible motor relies on water around it, so you must remember to remove it or switch it off when the basin drains.
Solar, mains or hybrid power
Solar is a great option for commercial lake aeration at the far end of a large site because it saves trenching a cable across the property.
A mains compressor can also sit up to 200 metres from the water, with air piped through a shallow buried hose. Our guide to solar water aerators for large lakes and commercial sites covers the trade-offs in more detail.
Sizing by depth, volume and shape
Base sizing on surface area, average depth and shape. Our guide to sizing an aerator for your water volume walks through the basic calculations. When you contact us, send:
- Surface area and average depth
- The deepest point
- An aerial photo or map pin showing the shape
- The distance to the nearest power point
- Whether the basin holds water all year
- What lives in or visits it
Running Stormwater Pond Aeration on an Unattended Site
Of course, many site managers and workers aren’t checking their stormwater basins every day. If this is the case, it’s a good idea to build aeration in from day one, rather than wait for someone to complain.
Here are some things every site manager should consider:
Commissioning and the first month
It’s crucial to start in stages if there are fish or other aquatic life in the basin. Run the system for:
- 15 minutes on day one
- 30 minutes on day two
- An hour on day three
Then add an hour each day until it runs around the clock. Staging stops oxygen-poor bottom water mixing through the whole basin at once.
You might notice some bad smells at the start. That’s normal. It’s just trapped gases escaping. Clear water takes weeks, so don’t judge it in the first fortnight.
A simple monitoring routine
The bubble pattern over each air station is the cheapest monitor you have. A steady, even boil means air is flowing. Ask whoever passes the basin to take a photo from the same spot each week and note clarity, smell and algae along the edges. Security or grounds staff can do it in a minute. If you can get a dissolved oxygen meter, take readings at dawn, when oxygen is lowest.
Servicing and who to call
Clean the air filters regularly. That alone does more for compressor life than anything else. Rocking piston compressors need a service kit every two years, and the air stations get blown out every few months.
Keep a spare filter on site. When something stops, call us. We stock spare filters, pump covers, manifolds and brass fittings, and we offer phone support to every customer.
Ingenia Lifestyle Lara’s detention pond was in bad shape when we took over. With aeration, weed and algae treatment and Biostim, visits fell from monthly to every two months.
A Worked Example: Stormwater Pond Aeration at a Data Centre Campus Lake
This is an illustrative scenario, not a real installation. Imagine a two-acre stormwater lake on the edge of a data centre campus. It holds water all year and reaches about 3 metres at the centre. Runoff from roofs and car parks feeds it, and a plant room sits close by.
A permanent pond means retention pond aeration suits it. The plant room rules out a surface unit that sprays, so subsurface diffusers go on the floor at the deepest point. Power is a long walk away, which points to solar or a compressor piped from the nearest outlet. Nobody visits daily, so the security patrol takes a weekly photo and a diary date covers the air filter.
Image: llustrative rendering of a solar-powered Air-O-Lator Carnival Aerator installed in a data centre campus lake.
Fit the Aeration to the Site, Then Keep It Running
Good stormwater pond aeration starts with the basin’s design, because a permanent pond and a basin that drains need different plans. Next comes the system type. After that, the main thing is to set up a disciplined maintenance routine to keep the water healthy and residents happy.
At Water Quality Solutions, we’ve been helping dam, lake and lagoon owners across Australia with aeration for over fifteen years. Send us your basin’s size, depth and power access, and we’ll recommend a system.