The dechlorination unit removes free chlorine and combined chlorine from the feedwater to prevent oxidative residual chlorine from causing irreversible oxidative damage to downstream polyamide reverse osmosis membranes, nanofiltration membranes, and ion-exchange resins, and is an essential protective step at the front end of the membrane system.
Process Principle
- Reducing agent method: reducing agents such as sodium bisulfite are dosed to reduce residual chlorine to chloride ions; the reaction is rapid and dosing is controllable.
- Activated carbon method: removes residual chlorine through adsorption and catalytic reduction by activated carbon, while also providing some organic matter removal capacity.
- Online residual chlorine analyzers and oxidation-reduction potential (ORP) monitoring are usually installed to control the dosage in an interlocked manner.
Product Features
- It can effectively reduce residual chlorine in membrane system feedwater to a controlled level, protecting polyamide membranes from oxidative degradation.
- The dosage is interlocked with online residual chlorine and ORP instruments to avoid underdosing or overdosing.
- The reducing agent method has a fast reaction and a small footprint, while the activated carbon method can simultaneously improve organic matter indicators.
- The equipment is simple and operates stably, making it a standardized front-end protective configuration for reverse osmosis systems.
Application Industries
- Front-end protection for reverse osmosis and nanofiltration systems using municipal tap water as the water source.
- Residual chlorine removal for circulating cooling water and water reuse systems.
- Feedwater pretreatment for ion-exchange resin and EDI systems.
- Dechlorination treatment for food and beverage and pharmaceutical process water.
Specifications and Models
| Parameter | Unit | Typical value |
|---|---|---|
| Treatment scale | m³/h | 5–1000 (typical value) |
| Influent residual chlorine | mg/L | 0.1–2.0 (typical value) |
| Effluent residual chlorine | mg/L | ≤ 0.05 (typical value) |
| ORP control range | mV | 200–350 (typical value) |
| Common reducing agent | — | Sodium bisulfite (SBS) |
| Contact time | s | ≥ 10 (typical value) |
The data in the table are common ranges for similar equipment and are for selection reference only; specific specifications, models, materials, connections, and control methods must be confirmed during the selection stage based on water quality, treatment scale, and site conditions.