Sunrui BalClor Electrochlorination BWTS Overview

Updated 2026-06-16

Sunrui BalClor is a widely installed electrochlorination ballast water management system from the Chinese manufacturer Qingdao Sunrui (CSIC). It combines a screen filter with side-stream electrolysis that generates total residual oxidant, dosed back into the main ballast line, with hydrogen management and neutralization on discharge. BalClor holds IMO and USCG type approval and is common across large bulk and tanker tonnage.

Sunrui BalClor Electrochlorination BWTS Overview

Key takeaways

BalClor uses side-stream electrochlorination, electrolysing a fraction of the flow at high concentration and dosing it back into the main line.
Side-stream design scales well to the very large ballast capacities of bulkers and tankers.
The process is salinity-dependent and may need salt dosing or face limits in fresh water.
Electrolysis produces hydrogen, requiring safe gas separation and dilution below the lower explosive limit.
Electrodes are the principal consumable, scaling and eroding and requiring descaling and eventual replacement.
TRO control governs dosing and discharge, with sodium thiosulfate neutralization before overboard discharge.
BalClor holds IMO and USCG type approval and completed IMO active-substance approval.

BalClor Treatment Principle

BalClor uses the side-stream electrochlorination approach common to many high-capacity systems. On ballasting the water passes a screen filter, and a small fraction of the filtered flow is diverted to an electrolysis unit where it is electrolysed at high concentration to produce a sodium-hypochlorite-rich oxidant stream. That concentrated stream is then injected back into the main ballast line to achieve the target total residual oxidant (TRO).

Treating only a side-stream keeps the electrolysis cell and rectifier far smaller than a full-flow chamber would need to be, which is one reason side-stream electrochlorination scales well to the very large ballast capacities of bulk carriers and tankers. The generated oxidant continues to inactivate organisms during the voyage holding time, contributing to D-2 compliance.

Because it relies on electrolysing chloride in seawater, BalClor is salinity-dependent. In low-salinity or fresh water the available chloride drops and dose can become difficult to achieve, so the system defines salinity operating limits and may require salt dosing for fresh-water operation.

Filtration and Hydrogen Management

The filter removes sediment and larger organisms on uptake, typically with a screen in the 50 micron class and automatic differential-pressure backflushing returned to the area of uptake. Reducing the solids and organism load improves disinfection efficiency and lowers oxidant demand.

Electrolysis of seawater generates hydrogen gas, so BalClor includes a gas-liquid separation and hydrogen dilution or venting arrangement that keeps hydrogen safely below the lower explosive limit. This gas management is a safety-critical feature and a regular inspection item, since blocked vents or failed dilution fans are serious faults.

The electrolysis cell with its electrodes, the rectifier and power supply, the TRO analyzer, the neutralization unit and the control system make up the rest of the architecture. The electrodes are the principal consumable, scaling and eroding over time and gradually reducing TRO output for a given current.

TRO Control and Neutralization

A TRO analyzer controls dosing on uptake to confirm the target concentration is reached, and verifies the residual on discharge to confirm it is within the maximum allowable discharge concentration. The control system interlocks treatment with flow and TRO signals, alarming or stopping the operation if parameters drift outside the approved band.

On deballasting the water passes through a neutralization step using a reducing agent such as sodium thiosulfate, dosed proportionally to the measured residual, bringing the oxidant below the discharge limit before the water goes overboard. Reagent stock for both the analyzer and neutralization needs active management with attention to shelf life.

TRO sensor drift, fouled measuring cells and depleted reagents are among the most frequent practical issues on electrochlorination systems, so a disciplined calibration schedule and managed reagent inventory are essential to avoid ballast operation delays.

Type Approval and Compliance

BalClor holds IMO type approval under the BWMS Code framework and, as a system using an active substance, also completed the IMO active-substance approval process that evaluates residual chemicals and disinfection by-products. Sunrui also obtained USCG type approval for BalClor, enabling discharge in US waters when the installed model and capacity are covered by the certificate.

The performance target is the IMO D-2 standard: fewer than 10 viable organisms per cubic metre for the 50 micron and larger class, fewer than 10 per millilitre for the 10 to 50 micron class, and the prescribed indicator microbe limits. The installed system must pass commissioning testing under MEPC.325(75) to confirm compliance aboard the specific vessel.

BalClor's scalability to high flow rates has made it a common choice on large bulk carriers and tankers, where full-flow electrolysis or UV would require larger or more numerous units.

Maintenance, Electrodes and Service

Electrochlorination maintenance centres on the electrolysis cell and electrodes, which scale and erode and require periodic inspection, descaling and eventual replacement. The rectifier and power supply, TRO analyzer with its reagents, neutralization dosing equipment, hydrogen-management components and the filter screen complete the regular maintenance scope.

Electrode condition directly determines achievable TRO, so electrode life and the descaling regime are central to long-term performance and operating cost. Acid cleaning of cells, where specified, is a routine procedure to remove scale and restore output.

Sea Clean AS supports electrochlorination BWTS operators with electrode and cell parts, TRO and neutralization reagents, filter spares and field service. Correctly specified electrodes, sensors and reagents preserve performance and the validity of the type approval.

Frequently asked questions

Who makes BalClor?

BalClor is made by Qingdao Sunrui, part of the China Shipbuilding Industry Corporation (CSIC) group. It is one of the more widely installed electrochlorination ballast water treatment systems, particularly on large bulk carriers and tankers, and holds both IMO and USCG type approval.

How does BalClor perform in fresh water?

Because it generates oxidant by electrolysing seawater chloride, performance falls as salinity decreases. BalClor defines salinity operating limits, and fresh-water operation may require salt dosing to reach the target dose. Owners with significant fresh-water trading should confirm the certified salinity envelope.

What is the main consumable on BalClor?

The electrolysis electrodes are the primary consumable. They scale and erode with use, gradually reducing TRO output for a given current, and require periodic inspection, acid descaling where specified, and eventual replacement. TRO analyzer reagents and neutralizing chemical are also recurring consumables.

Is BalClor approved for US waters?

Yes. Sunrui obtained USCG type approval for BalClor in addition to its IMO type approval and active-substance approval, so it can be used for discharge in US waters when the installed model and capacity are covered by the certificate. The installed unit also requires MEPC.325(75) commissioning testing.

Sources

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