Biosperse Microbiocide for Cooling Towers at Salalah Free Zone Plants
Microbial slime in an open cooling tower cuts heat transfer, feeds under-deposit corrosion and raises the Legionella risk. Biosperse microbiocide is the non-oxidising biocide we supply to control it. At the Salalah Free Zone methanol, ammonia and cement plants, you slug dose Biosperse on top of your oxidiser programme. It kills the bacteria, algae and fungi inside the biofilm that chlorine or bromine does not reach. We ship it in 25 litre and 210 litre packs from our Barka warehouse to Salalah and the rest of Dhofar.
What Biosperse microbiocide is and how it works
Biosperse is a broad-spectrum biocide for plant water systems. Our product record lists control of spore and non-spore forming bacteria, SRB's, Fe-bacteria, algae and fungi. Its long lasting killing effect means you add biocide less often. It is also sold as Biosperse 250, Biosperse - 50 and VCT - 4804. Our part number is RXSOL-40-4092-025 Biocide Biosperse.
It is an isothiazolinone biocide. Our MSDS lists 5-chloro-2-methyl-4-isothiazolin-3-one (CAS 26172-55-4) at 1.1% by weight, with magnesium nitrate (CAS 10377-60-3) at 1.0- 7.0% by weight. Isothiazolinones react with nucleophiles inside the cell and switch off its enzymes. They take minutes to hours to work, while an oxidiser works in seconds. In return they penetrate biofilm, act against sulfate-reducing bacteria (SRB) and typically leave a residual for several days.
Our record recommends Biosperse for systems with a pH between 6 and 9.5. It is easily detoxified, so you can use it in environmentally sensitive areas. It works in both open and closed water systems, including recirculating cooling towers, pasteurisers, air washers and membrane separation systems.
| Item | Biocide Biosperse |
|---|---|
| Part number | RXSOL-40-4092-025 |
| Also known as | BIOSPERSE 250, Biosperse - 50, VCT - 4804 |
| Application | Control of bacteria, fungi and algae in recirculating water systems, pasteurizers, air washer systems and membrane separation systems |
| Appearance | clear, light green liquid |
| pH | 3.5 |
| Density (kg/m3) | 1030 |
| Solubility | completely miscible in water |
| Flash point | none |
| Recommended system pH | 6 to 9.5 |
| Typical dose (isothiazolinone class) | 50 to 100 ppm of product every 3 to 7 days; confirm against the TDS |
| Packing | 25 litres, 210 litres |
The physical data above are typical values and should not be read as specifications.
Why cooling towers at Salalah Free Zone plants foul faster
Open towers in Dhofar carry a seasonal load that northern plants see less of. The khareef runs from June to September, and the fans pull humid monsoon air and windblown dust through the fill. That air brings nutrients and spores into warm circulating water. Algae grow on sunlit decks and distribution basins, and slime builds in the fill and on exchanger tubes.
Methanol and ammonia units at the Salalah Free Zone run large recirculating systems, and the cement plants at Raysut add fine dust of their own. A continuous chlorine or bromine feed keeps free-floating bacteria down. It does not reach organisms sheltered inside a slime layer. A non-oxidising cooling tower biocide closes that gap.
Oxidising vs non-oxidising biocide: using Biosperse with chlorine or bromine
Oxidisers such as chlorine and bromine act within seconds. You feed them continuously at a low residual, typically 0.2 to 0.5 ppm free halogen. Non-oxidisers act more slowly, persist longer and reach organisms inside biofilm. The usual programme combines the two. A low oxidant residual cuts planktonic bacteria and breaks down the slime matrix (EPS). A slug dose of a non-oxidiser such as Biosperse then penetrates and kills the biofilm.
Dose the two at different times and at different dosing points. Isothiazolinone stability can be limited at high pH and with reducing agents. Before the first slug, check that Biosperse is compatible with your other treatment chemicals, including any bisulfite or dechlorination feed. A biodispersant breaks up biofilm and suspends the bacteria so the biocide can reach them, and it belongs in a full biocontrol programme. If the tower is heavily fouled, clean it mechanically before you start the biocide programme.
Typical dosing: slug dose, holding time and rotation
Our record does not give a fixed dose for Biosperse. Plan the first programme on the typical figures for this product class, then confirm them against the product TDS. For isothiazolinone biocides, a typical shock dose is 50 to 100 ppm of product every 3 to 7 days.
Holding time decides whether the dose works. Typical guidance is 4 to 8 hours with blowdown closed after the slug. A second rule ties the holding time to your system: keep blowdown closed for at least 2 times the system half-life, for example 12 hours for a 6-hour half-life. Use whichever is longer.
pH also changes the dose you need. Lab tests on real cooling tower water found that about 1 ppm of isothiazolinone active gave 99% kill of Legionella in 6 hours at pH 8.0. At pH 6.7 the same kill needed roughly double the dose.
Rotate the primary non-oxidiser every 2 to 4 weeks to prevent resistance. Other non-oxidising classes used in rotation include quaternary ammonium compounds and THPS, which also leave a residual. DBNPA and glutaraldehyde kill fast, but their residual is short and they are not suited to continuous dosing.
Worked example: litres for each shot on a plant tower
Take a methanol or ammonia plant tower with 500 m3 of water in the basin, pipework and exchangers, and a target slug of 50 ppm of product.
- A 50 ppm dose by weight means 50 grams of product for each cubic metre of water, so 500 m3 needs 25 kilograms.
- The typical density is 1030 kg/m3, so one litre weighs 1.03 kilograms and 25 kilograms is about 24.3 litres.
- At the top of the typical range, 100 ppm, the same tower needs 50 kilograms, about 48.5 litres.
On this system one 25 litre pack covers one 50 ppm shot, and a 210 litre drum covers roughly eight. Before you set the dose, work out your own system volume from the basin dimensions and pipework or from a tracer test. To estimate half-life in hours, multiply system volume by 0.693 and divide by the hourly water loss through blowdown and drift in m3.
Monitoring: dip slides, CFU/mL, SRB and ORP
Check results every week so you can tell whether the programme is working:
- Total bacteria by dip slide or plate count: target below 104 CFU/mL, take action at 105.
- SRB test: a positive result at 28 days is an action signal.
- ORP during oxidiser dosing: 600 to 700 mV. A reading below 450 mV means the oxidiser is exhausted.
- Free halogen residual: 0.2 to 0.5 ppm.
Take a dip slide sample before the slug and another two or three days after it. If counts do not fall, check the dose and holding time first, then rotate the biocide.
Packing, storage, hazards and handling in Dhofar heat
We supply Biosperse in 25 litre and 210 litre packs. Keep containers tightly closed and out of direct sunlight. In Salalah yards and port laydown areas, store them in shade, not on an open rack beside the tower. Our record does not state a shelf life, so ask for it when you request a quote.
Isothiazolinone cooling-water microbiocides of this type carry a Danger signal word because they are corrosive and cause serious eye and skin damage. When you decant or dose, wear chemical-resistant gloves, goggles or a face shield and protective clothing, and follow the product MSDS. Do not use these products in potable water systems or anywhere potable water could be contaminated. Keep the dosing line away from drinking water tanks and coolers.
Keep blowdown closed for the full holding time so the slug does not go straight to drain. Check the discharge conditions in your plant's environmental permit before you release treated water.
Where to buy Biosperse microbiocide in Salalah
Salalah Chemical (RXSOL group, Oman) delivers Biosperse from our Barka warehouse to Salalah, the Salalah Free Zone, Raysut and sites across Dhofar. Phone +968 77333599, or send us your system volume and the number of slugs you plan each month on WhatsApp. We will size the order in packs and drums. Dispersants and corrosion inhibitors for the same tower are listed under our cooling water chemicals, and the full Salalah Chemical product range covers the rest of your plant.
If you also run plants in the north, order the same product from Sohar Chemical for deliveries to Sohar port and the plants around it, or from Muscat Chemical for sites around Muscat and Barka.
To request a quote for Biosperse, send us a WhatsApp message on +968 77333599 or use our quote request page.
Frequently asked questions
What is the difference between oxidising and non-oxidising biocides?
Oxidisers such as chlorine and bromine kill within seconds, and you feed them continuously at a low residual, typically 0.2 to 0.5 ppm free halogen. Non-oxidisers such as isothiazolinone biocides act over minutes to hours. They penetrate biofilm, act against SRB and leave a residual that typically lasts several days.
How long must blowdown be closed after dosing Biosperse?
Typical guidance for isothiazolinone biocides is 4 to 8 hours with blowdown closed. Also keep blowdown closed for at least 2 times the system half-life, for example 12 hours for a 6-hour half-life, and use whichever period is longer.
Can Biosperse be used with chlorine or bromine?
Yes, as part of a combined programme. A low oxidant residual controls free-floating bacteria, and a slug dose of Biosperse kills the biofilm. Dose them at different times and points, and check compatibility first, because isothiazolinone stability can be limited at high pH and with reducing agents.
Is cooling tower biocide safe for potable water systems?
No. Isothiazolinone cooling-water microbiocides are not recommended for potable water systems or where potable water could be contaminated. They carry a Danger signal word because they are corrosive and cause serious eye and skin damage.
Where can I buy cooling tower biocide in Salalah?
Salalah Chemical (RXSOL group, Oman) supplies Biosperse, part number RXSOL-40-4092-025, in 25 litre and 210 litre packs. We deliver from our Barka warehouse to Salalah and Dhofar. Call or WhatsApp +968 77333599 for a quote.