Biofouling & Biofilm Control

Biofilm is the first stage of biofouling and the foundation of the rest. A biofilm is the thin, slimy layer that bacteria build on a surface — cells held in a sticky matrix they secrete themselves, which protects them from the chlorine, biocide and heat aimed at them. Biofouling is the broader term for everything that accumulates on top: algae, then the mussels, barnacles and other organisms whose larvae settle preferentially on an existing film. In a freshwater cooling tower the problem usually stops at biofilm and slime; in a seawater intake it becomes shell beds that block a line. Either way, controlling the film is the lever — which is why HydroFLOW® acts on the biofilm’s matrix rather than on the organisms one by one.

Three things together: a wetted surface, nutrients and time. Cooling water is warm, oxygenated and continuously topped up with nutrients from the make-up, so bacteria attach and multiply on fill, basins and condenser tubes; seawater adds a living supply of larvae with every litre drawn from a harbour or estuary. Low flow and standing water accelerate it — dead legs, lay-up periods, weekend shutdowns and idle lines are where a film consolidates into something a shock dose no longer shifts. Scale makes it worse, because a rough mineral surface gives biofilm a foothold. At a 180 MW LNG plant in China, seawater condensers combined biofilm and scale and needed cleaning every four to six months; at the V&A Waterfront in Cape Town, mussels and barnacles had established inside a 200 mm line until strainer blockages made jetting routine.

The conventional toolkit is screening to keep the large organisms out, chlorination or a copper-anode system to deter settlement, and periodic mechanical cleaning — jetting, hot-soaking, pigging or opening the exchanger — to remove what settles anyway. Each has a cost the discharge consent, the maintenance budget or the outage log records. HydroFLOW® adds a physical layer that works on the surface itself: with the biofilm unable to consolidate, larvae have nothing to settle on and established growth detaches. The documented records are controlled comparisons. At a Chilean desalination plant, the treated suction line ran 223 days with no mussels while the untreated control line grew mussels over 3 cm; at a Hong Kong seawater pump station, the treated plate heat exchanger held 14–18% higher seawater flow than its untreated twin over six months and stayed largely unblocked while the untreated unit blocked to a depth of three feet.

Almost always biofilm — a community of bacteria, and in sunlight algae, held together in the slimy matrix they secrete — rather than a chemical residue. The green or brown film on tower fill and basins is the visible part; the costly part is the thinner film on condenser tubes, which insulates heat transfer several times more effectively than scale of the same thickness and shelters bacteria from the biocide dose. Two of the usual tells are biocide demand that keeps rising and bio-counts that fall after each treatment and drift back. HydroFLOW® addresses the film rather than the count: at a 2.3-million-square-foot US office complex, cooling-tower bio-counts fell from approximately 100,000 CFU to below 1,000 within days of installation, alongside reduced scale and biofilm, and at a US plastics plant, recirculating water baths showed no algae after chlorine dosing was cut 75%.

Scepticism here is earned. The best-known independent test, ASHRAE research project RP-1361 (2010), ran five non-chemical devices — magnetic, electrostatic, pulsed-field, ultrasonic and cavitation — in a model cooling tower and found none of them measurably reduced microbial populations. We would not argue with that result for those devices, and we would make three distinctions. First, mechanism: HydroFLOW® is not a magnet or a static coil; it induces a patented ~150 kHz signal into the water that destabilises the biofilm matrix and flocculates suspended cells, and it is sized to the pipe and the flow. Second, evidence: the records on this page are site measurements with comparators, not brochure claims — a treated intake line against an untreated one for 223 days, a treated plate heat exchanger against its untreated twin for six months, bacteria counts of 300,000 falling to 9,000 CFU on seawater condensers. Third, verifiability: we recommend judging it the way those sites did, with a unit on one line measured against another, and we will help set the protocol.

It changes the surface they depend on, not the organisms themselves. Bacteria in a biofilm are held to the pipe wall by a matrix of polymers they secrete; the induced signal destabilises that matrix, so established film detaches in fragments and new film cannot consolidate. Cells and particles freed into the water pick up a charge and clump together in turbulent flow into flocs large enough for strainers and filters to catch — and bacteria that were sheltered inside the film are exposed to whatever residual chlorine or biocide the site already runs. Mussel and barnacle larvae settle preferentially on an existing biofilm, so a surface that cannot hold a stable film gives them nothing to build on. That is why a car carrier’s cooling plates were found clean of barnacles after 13 months with no chemicals used, and why the Cape Town seawater line discharged its settled growth within two weeks and stayed clear for the six-month trial.

Yes — seawater systems are where much of the biofouling record was built, because the fouling is fastest and the chemical route is most constrained by discharge limits. The unit installs around the outside of the pipe and never contacts the flow, so salinity, GRP or lined pipework and lagging make no difference to the signal. Documented seawater sites include seawater-cooled chiller plants in Hong Kong (tubes free of biofilm at two months, COP up 10–15% on a 14-month log, within a 0.2 ppm chlorine limit), a seawater-cooled LNG power plant (bacteria down 97%), a desalination intake in Chile (223 days without cleaning), a Tasmanian zinc smelter drawing from the Derwent Estuary (strainer cleaning interval from two weeks to 4–5 months in high-flow areas) and a container ship’s fresh-water generator (CIP cleans from about 36 to 5 a year).

Indirectly but materially. The WHO describes Legionella surviving and growing inside the biofilms that develop in water systems, sheltered from the temperature and disinfectant meant to control it — which is why counts so often fall after a treatment and drift back. Disrupting the film lets the existing controls reach the bacteria. At an Indiana hospital, potable-water Legionella fell from 7 CFU/mL to 1 CFU/mL or non-detectable within 16 days of installation and stayed stable after 15 months, and a proposed $75,000 treatment system was not required; at Grand Hotel Terme di Comano, a programme that combined HydroFLOW® with thermal shock and purging reported certified results below 10 CFU/L in every June sample. HydroFLOW® is not a disinfectant, so the risk assessment, temperature regime and sampling stay in place — our Legionella page sets out the full picture.

No, and not on day one. HydroFLOW® does not kill organisms or sanitise water: it is not a disinfectant and not a biocide, and any claim that a device alone will keep a cooling tower or potable system compliant should be treated with suspicion. What the documented sites show is the workload changing once the biofilm stops sheltering bacteria — a California medical centre cut biocide 75% while holding CFU below 1,000, with side-stream filtration added alongside; a US apple packhouse held non-detect counts as chlorine fell from 40–50 ppm to 10 ppm; and the China LNG plant worked within its existing electro-chlorination. Reductions are measured against each site’s own programme, with its sampling, consent and risk assessment intact; where our assessment is that biofilm is not your problem, we will say so.

It is not a filter, and the first weeks prove it: expect more at the strainers, not less. Established film and settled growth detach as the signal takes hold, and that material has to go somewhere — at the V&A Waterfront, large amounts of sea life and mussel fragments were discharged at the intake filter after two weeks before the line settled to minimal material; at Obolon Brewery, a fully blocked filter rinsed clean with running water by day 25. Keep screening and filtration in place, check strainers more often in the first month, and size for the release if a line is known to be heavily fouled. If your primary problem is suspended solids or supply quality rather than growth, filtration is the answer and we will tell you so.

Yes to the first: the unit installs around the outside of the existing pipe — no cutting, no drain-down, no dry-dock — typically in under an hour with the system running, which is how the Cape Town seawater line was fitted between pump and exchanger with no shutdown required. Results depend on what you measure. Bio-counts move first — the US office complex saw them fall within days. Settled growth releases over weeks — Cape Town discharged in two weeks. Surfaces are clean over months — Hong Kong’s condenser tubes at two months, a Middle East RO plant’s cartridge life rising over the following year. And the records that prove it take a season or more: Chile’s 223-day controlled run and a 14-month COP log. Lay-ups and shutdowns do not pause it — the signal keeps working on standing water.