Overview
Disinfection is the controlled inactivation of pathogenic and nuisance microorganisms such as bacteria, viruses, algae, protozoa, and biofilm-forming organisms. In raw water treatment, it is both the final step in potable water production (primary disinfection to achieve a safe microbial count) and an ongoing control measure to prevent microbial regrowth in distribution systems (secondary disinfection residual).
In industrial water systems, disinfection serves a different but equally critical function: controlling biofouling in cooling towers, heat exchangers, and process water loops. Uncontrolled microbial growth in these systems leads to biofilm formation, which dramatically reduces heat transfer efficiency, accelerates under-deposit corrosion, and in the case of Legionella, creates a public health hazard requiring mandatory management.
Chlorine chemistry at a glance: Liquid chlorine (Cl₂) dissolves in water to form hypochlorous acid (HOCl) and hydrochloric acid. HOCl is the active disinfecting species. It is significantly more effective as a biocide than the hypochlorite ion (OCl⁻) that predominates above pH 7.5. This is why maintaining pH in the 6.5–7.5 range maximises disinfection effectiveness per unit chlorine dose. Lamurindo supplies liquid chlorine in cylinders, ton containers, and bulk tankers, see the Liquid Chlorine product page for supply details.
Disinfectant Types
Applications
| Application | Disinfectant | Notes |
|---|---|---|
| Municipal potable WTP, primary disinfection | Liquid chlorine or NaOCl | Contact time (CT) product must meet regulatory target for 3-log Giardia inactivation; dosing at post-filtration point maximises CT and minimises chlorine demand |
| Distribution system, secondary residual | Chlorine or chloramine | Free chlorine residual 0.2–1.0 mg/L at consumer tap; chloramines preferred in long distribution systems to minimise THM formation |
| Industrial cooling tower, continuous biofouling control | NaOCl or BCDMH (continuous low dose) | Target free halogen 0.2–1.0 mg/L; BCDMH preferred where cooling water pH >8.0; shock dosing required during Legionella risk events |
| Seawater intake, biofouling prevention | Liquid chlorine or NaOCl (intermittent or continuous) | Prevents mussel, barnacle, and biofilm accumulation on intake screens and condenser tubes; typically 0.5–1.0 mg/L free residual at heat exchanger outlet |
| Process water disinfection | NaOCl or ClO₂ | ClO₂ preferred where NOM is present and THM formation must be minimised |
| Fire water system maintenance | NaOCl (periodic shock dose) | Prevents Legionella colonisation and biofilm growth in stagnant sections of firewater mains; important for HSE compliance on process plant sites |
Petrochemical & LNG Applications
Industrial facilities in the oil & gas, petrochemical, and LNG sectors operate multiple water systems where microbial control is both operationally and safety-critical. Lamurindo supplies liquid chlorine nationally, which is the preferred disinfectant for large industrial sites due to its cost effectiveness and high active chlorine content.
In LNG plant seawater cooling systems, the large volumes of seawater circulated through the liquefaction process and open rack vaporisers (ORVs) are highly susceptible to biofouling from marine organisms, such as mussels, barnacles, and microbial biofilm. Continuous or intermittent chlorination at the seawater intake prevents this fouling and protects heat exchanger efficiency. Strict monitoring of chlorine residual at the discharge point is required to comply with AMDAL and KLH discharge limits for active halogens.
In refinery and petrochemical cooling towers, the warm, nutrient-rich recirculating water is an ideal growth environment for bacteria, algae, and Legionella. Continuous biocide dosing, typically halogen-based (chlorine or bromine) combined with periodic non-oxidising biocide additions maintains microbial counts within acceptable limits and prevents biofilm formation in heat exchanger bundles. Legionella risk assessments are a regulatory requirement for all cooling towers in Indonesia under Permenkes guidelines.
In firewater systems on process plant sites, water stagnates for long periods between tests or uses. Periodic chlorination shocks prevent Legionella colonisation and maintain water quality for emergency use.