SWRO or BWRO in Saudi Arabia? Let Your Water Decide

Neither technology is inherently better. Each is designed for a different feedwater salinity and operating condition.

These figures are design guidelines, not performance guarantees. A reliable proposal should state the feedwater conditions on which its capacity, recovery, product-water quality and energy figures are based.

If your feedwater is brackish, the next design question is not simply "one stage or two." The number of membrane stages is generally determined by flow, recovery and concentration limits, while a second RO pass is normally used when the product-water quality requirement cannot be met in one pass. KONCHE's single-stage and double-stage RO systems can be configured around the actual water analysis and required product-water quality.

Brackish water sits between fresh water and seawater. A commonly used working range is approximately 1,000–10,000 mg/L TDS (Greenlee et al., 2009, Water Research).

Saudi seawater should not be treated as one fixed number. Red Sea salinity generally increases toward the north, while Arabian Gulf salinity is commonly higher than the open-ocean average and can vary further in shallow or enclosed areas. PSU is a salinity unit and should not be treated as an exact one-to-one replacement for mg/L TDS.

Groundwater also varies from well to well. Even when two wells have similar TDS, their hardness, silica, sulfate, iron and alkalinity may be very different. Each active source should therefore be sampled and tested separately.

Large Saudi reference projects illustrate the basic geography: coastal desalination plants such as Ras Al-Khair use seawater treatment, while brackish-water plants such as Al Wasia draw from inland wells. Your own project, however, must be designed from its intake analysis — not from a nearby project or a regional average.

Pretreatment is not a fixed list of filters. It should be selected to protect the membranes from suspended solids, scaling, fouling and biological growth.

At a minimum, provide a recent laboratory report covering:

• TDS and conductivity: establish the salinity range, membrane category and approximate operating pressure.
• pH and alkalinity: affect scaling calculations and chemical dosing.
• Total hardness, calcium and magnesium: indicate the risk of carbonate and other mineral scale.
• Silica: can limit achievable recovery, particularly in Saudi groundwater.
• Sulfate, barium and strontium: help identify low-solubility scale risks.
• Iron and manganese: may require removal before the RO system.
• Turbidity and raw-water SDI, where available: indicate the suspended-solids and fouling load.
• TOC and microbiological results: help assess organic and biological fouling risk.
• Temperature: affects membrane flow, salt passage and required pressure; seasonal minimum and maximum values are more useful than a single reading.
• Boron and algae information for seawater sources: may affect process configuration and pretreatment.

The supplier should also define the required SDI at the RO membrane inlet and explain how the proposed pretreatment will achieve it. A buyer cannot normally provide "SDI after pretreatment" before that pretreatment system has been designed and installed.

Typical process arrangements

• Seawater: intake or beach well → media filtration or UF → cartridge filtration → chemical dosing → high-pressure SWRO.
• Brackish groundwater: well → media filtration as required → cartridge filtration → chemical dosing or softening as required → BWRO.

These are only process outlines. The filtration area, chemical dose, membrane array, materials and cleaning provisions must all be sized for the actual water and production target. Where the feedwater requires a stronger solids barrier, ultrafiltration may be used ahead of RO.

Tell the supplier exactly how the treated water will be used. "Domestic water" is too ambiguous for a design specification.

Use clear categories such as:

• non-potable utility or service water;
• irrigation water;
• industrial process water;
• potable water for drinking, cooking or food contact.

Each use may require a different product-water limit, post-treatment step and compliance route. Where drinking-water requirements apply, standards such as GSO 149 and the requirements of the relevant Saudi authority should be confirmed by the project owner and local consultant. Potable-water production should be treated as a defined, regulated scope rather than assumed from an RO product-water figure. KONCHE's drinking-water systems are intended for projects where that separate scope has been established.

UV also needs to be specified correctly. A UV sterilizer can reduce microorganisms passing through the unit, but it does not remove salt and leaves no disinfectant residual in a storage tank or distribution network. Tank hygiene, circulation, cleaning and residual disinfection may still be required.

The lowest equipment quotation is not always the lowest-cost water solution. Compare the total cost of ownership over the expected operating period:

Ask every supplier to state the following on the same basis:

This comparison prevents an apparently low-priced package from becoming expensive after installation, or from missing critical items needed to operate safely.

Resolve the permitting and concentrate-disposal route before the equipment is ordered. The following is general project guidance, not legal advice.

1. Groundwater licensing: Wells and groundwater use in Saudi Arabia are regulated by the Ministry of Environment, Water and Agriculture (MEWA). In August 2024, MEWA updated licence conditions for groundwater use and related well services. Check the current requirements through the Saudi Press Agency notice and the national portal's licence service, and include the approval period in the project schedule.
2. Environmental permitting: Desalination facilities and water discharge may require approval from the National Center for Environmental Compliance (NCEC). Confirm the applicable permit category with the project's environmental consultant.
3. Concentrate disposal: A coastal SWRO project may be able to use a permitted marine outfall, subject to assessment and design. Inland BWRO projects may need an evaporation pond, injection arrangement, approved sewer connection or zero-liquid-discharge solution. The feasible route depends on the site and can materially change the project cost.

A credible supplier should ask where the concentrate will go and identify the reject flow and salinity. Final permitting responsibility and the selected disposal method should be recorded clearly in the project scope.

Remote camps, construction projects, farms, coastal hotels and temporary facilities often benefit from a containerized water-treatment system. Pretreatment, RO, controls and optional disinfection can be assembled and tested before shipment, reducing site installation work and shortening commissioning time.

Both SWRO and BWRO can be containerized, but a container does not eliminate site requirements. Before choosing this format, confirm:

• road and crane access, container weight and lifting plan;
• foundation, drainage and ventilation;
• feed, product and concentrate connections;
• available power and generator compatibility;
• chemical storage and operator access;
• ambient-temperature control;
• space for tanks, cleaning equipment and future maintenance.

A containerized system is particularly useful where deployment speed or relocation matters. A conventional plant room may be more suitable when capacity, expansion, maintenance access or permanent site integration is the priority.

Send the same data pack to every supplier so that the proposals can be compared fairly.

KONCHE has manufactured water-treatment equipment since 1997, including commercial RO systems from 0.25 to 50 m³/h. To obtain an engineering review, send your water analysis, required capacity, intended water use and site information to project support. You can also request a quotation.

The first question should not be "What is the cheapest membrane?" It should be "What does my water require, and what will this system cost to operate reliably?"