can DBNPA replace Chlroine

[Watro]

Helow,

We have a wastewater RO plant project to be designed to treat effluent from an MBR treatment plant. The feed water to our RO is chlorinated downstream MBR plant before being stored in a big tank, from where it is pumped to WWRO plant. FYI, feed to MBR is mixture of refinery WW and a portion of them is sanitary WW

In RO we just have pretreatment with dosing Acid, Antiscalant and SBS followed by Cartridge filter and biocide just before RO

The RO membrane OEM recommended to dose non-oxidizing biocide continuously to avoid fouling and instructed that it should reach RO membranes. The proposed biocide is DBNPA - Note - Using ammonia to produce Chloramine is not permitted at site. Our Client is also insisting on SBS dosing, since the feed WW is chlorinated. However at the same time, the SBS deactivates DBNPA as well, meaning that no biocide will reach RO membranes. The DBNPA supplier advised, with DBNPA dosing online, in fact no need of chlorination downstream of MBR (which is not in our B/L)

The question, is DBNPA could give any residual effect compared to Chlorine? The bacterial disinfection could be controlled maintaining the FRC. Is it such criteria exists on DBNPA or is it possible to potentially replace an effective oxidizing disinfectant such as Chlorine. Thanks in advance for your advise

Thanks
NM

 

[bimr]

It is understood in the membrane industry that thin film composite polyamide membranes have limited resistance to chlorine based oxidants. Therefore, operators have relatively few options regarding chemicals which can be safely used to disinfect RO/NF systems and prevent biogrowth/biofouling. One option is the chemical, 2,2-Dibromo-3-nitrilopropionamide (DBNPA), which is a fast- acting, non-oxidizing biocide which is very effective at low concentrations in controlling the growth of aerobic bacteria, anaerobic bacteria, fungi and algae.

Dow (manufacturer of DBNPA) states:

"A material suited for this application is DBNPA (2,2, dibromo-3-nitrilo-proprionamide), which
has the following characteristics:
• Compatible with the membrane
• Fast acting
• Cost effective
• Acceptable transportation, storage, stability and handling characteristics
• Broad spectrum control (e.g., planktonic and sessile organisms); algae control is seasonal and
situational
• Biodegradable"

Although DBNPA is useful as a disinfectant, DBNPA should not be used for storage since it is not long-acting.

No, DBNPA will not have a residual effect like chlorine. You should disinfect after the RO treatment. If you are using a disinfectant prior to the RO system, you need to use a disinfectant that is compatible with the RO membranes.

http://www.membranes.com/docs/tsb/TSB110.pdf