Scotmas Ultra-Pure chlorine dioxide replaces the need for any Chlorination Facility specified for Seawater Biofouling Protection – by replacing hypochlorite dosing with ultrapure chlorine dioxide dosing – and this can be achieved from a single chlorine dioxide installation, which is already specified for Product Water dosing.

On the sea water side low level discontinuous ultrapure chlorine dioxide will provide macro-fouling protection (i.e. prevent Intake Structure colonisation from algae, mussels and barnacles) and micro-fouling protection (i.e. prevent the proliferation of biofilms).

Ultrapure chlorine dioxide can be dosed to feedwater pre‑treatment systems (e.g. DAF systems, Ultrafiltration Systems, Cartridge and MMF filters), chlorine dioxide improves flocculation, reduces coagulant dosing and improves filter performance, it prevents the settlement and proliferation of biofilm, reducing backwash frequency and extends plant longevity.

The operating cost associated with membrane fouling arises from increased osmotic pressure from fouling formation, which leads to increased operating expenditure due to higher energy consumption, reduced membrane longevity and additional CIP cleaning – studies have reported that the cost of biofouling in a membrane system is around 20 to 30% of operating expenses.

Basic design of chlorine dioxide generation systems has not changed much since the 1980s – sodium chlorite is mixed with hydrochloric acid in a reaction vessel before being injected into the water stream – however, this chlorine dioxide acidification process can lead to traces of chlorine from side-reactions from poorly optimised or designed generation processes, these undesirable by‑products can have a harmful effect on RO membranes and so there has been a reluctance to employ traditional chlorine dioxide system design for SWRO Intake macrofouling protection.

However, Scotmas Ultra-Pure chlorine dioxide is free-from chlorine and from other harmful by-products and only the chlorine dioxide molecule is permitted to pass through the system creating a solution with 99.7 % Purity.

As the chlorine dioxide molecule itself does not damage RO membranes, this recent Scotmas technology development of in-situ Ultra-Pure chlorine dioxide generation provides a paradigm shift for SWRO designers and operators to consider.

Chlorine Dioxide is the primary biocide of choice for the disinfection of desalinated water across the MENA region.

In addition to pre-treatment, Ultra-Pure chlorine dioxide is also beneficial for water disinfection post treatment, in order to maintain water quality in storage tanks and the distribution networks.

Chlorite and chlorate in the produced solution, which is ubiquitous with traditional chlorine dioxide technologies, is separated and removed with Scotmas ultrapure chlorine dioxide technology, this ensures that no undesirable generation by-products are introduced into the desalinated water along with the Ultra-Pure chlorine dioxide solution.

With the exception of the Scotmas Bravo Ultra-Pure, other Chlorite / Acid chlorine dioxide generators allow unreacted reagents and undesirable generation by‑products, including chlorite and chlorate, and potentially chlorine, to flow through to the water supply along with the produced chlorine dioxide – until recently the WHO, the USEPA and the EU have not viewed this as being a significant issue. However, since the publication of the EFSA and JECFA reports regarding health concerns from chlorate, the lower 0.25mg/l MCL limits will create new compliance problems for regions where international water quality standards (e.g. WHO, USEPA, UKDWI or EU DWD) are being applied.

Innovative patented technology developed by Scotmas (Patent No. GB2575179), provides end-users with the opportunity to eliminate any risk of introducing undesirable by-products including chlorate and chlorite into their water supply via the chlorine dioxide generation system.

Chlorine Dioxide proves excellent resistance to bulk-decay in hot climates, providing a disinfection residual in a 375km long transmission main in desert climates.

Extensive third party testing undertaken in Saudi Arabia has conclusively shown that disinfection dosing from Scotmas Ultra-Pure Chlorine Dioxide technology was high effective in protecting the water between desalination plant and the high point terminal storage reservoir.

This recent study demonstrated that a chlorine dioxide dose of ~0.4 ppm to the product water entering a 375km long 60” cement line steel transmission main consistently provided chlorine dioxide residuals of >0.2ppm at the end.

The trial was conducted between April and July 2023 with average day temperatures in June and July reaching >42°C (107°F). The transmission main entered service in 1995 and the water transit time is 4 to 5 days.