Flowback Water Treatment - Shale Gas

Chemical Free UV Disinfection of Flowback Water   

Natural oil and gas extracted from shale rock formations has become one of the fastest-growing oil and gas sectors worldwide.  Using a process known as hydraulic fracturing or 'fracking' , the process requires large volumes of clean, sterile water to be injected into the shale formation to release the gas trapped between the rock.

Typically, 30% to 80% of the injected water, together with formation water and other contaminants returns from the well in the form of flowback water.  Large scale removal of flowback water poses significant problems for operators due to the high level of truck movements required to remove waste flowback and deliver fresh water, plus the high costs of offsite wastewater treatment.  Therefore investment in onsite water treatment solutions that allow flowback water to be recycled and reused for additional well stages have become a priority for the unconventional Oil and Gas industry.

ABOVE: atg UV Technology Mobile UV Treatment Package for Unconventional Oil and Gas flowback water treatment.

atg UV Technology have provided specialist UV treatment packages for the disinfection of flowback water before reinjection.  Using a specially developed UV system purposely designed to treat flowback water, the atg UV Technology solution targets a range of microorganisms including SRB’s (Sulphate Reducing Bacteria), Acid Producing Bacteria and Slime Forming Bacteria.

Traditionally large volumes of biocide such as Glutaraldehyde and THPS have been used to chemically dose Flowback Water before reinjection in order to protect against bacterial growth.  However strong public and environmental opposition to the use of chemicals, plus the rising costs of biocides, handling, site storage concerns plus an appetite by operators to reduce wherever possible the amount of chemicals added to the process has seen operators worldwide turn to UV treatment as an alternative solution.   

By using UV treatment as a primary solution for reducing bacteria, operators can significantly reduce the required volumes of chemical biocides from the process typically by 90%, only requiring a small residual to prevent re-contamination downstream of the UV system.  In some cases, operators have been able to eliminate biocide use altogether, significantly improving their environmental profile. 

 

Benefits of UV Treatment: -

  • UV has been identified as a Best Available Technology for UK shale gas by the Environment Agency and DECC.
  • UV is a chemical-free, safe solution, widely used for drinking water and cannot be overdosed.
  • Eliminates chemical transportation, storage and handling.
  • Onsite water treatment & flowback water reuse significantly reduces truck movements
  • Water reuse of flowback significanly reduces operational costs.
  • Environmentally friendly, green technology
  • Safe, low risk technology to operate 
  • Very low operation & maintenance requirements
  • Compact footprint & low weight solution
  • Reduced OPEX costs compared to other available technologies
  • Successful, field proven technology

 

Advanced Oxidation to Remove Chemical & Organic Contaminants

atg UV Technology have recently patented a unique Advanced Oxidation Process known as Keratox for the treatment and removal of organic and chemical contaminants from flowback water returning to the surface following hydraulic fracturing.   

Utilising atg UV Technology’s UV treatment systems in combination with a unique Titanium Dioxide (Tio2) catalyst, the Keratox advanced oxidation solution can be used to target and remove contaminants detailed in regulations such as the OSPAR list of chemicals for priority action and EU priority substances watch list e.g. Polyaromatic hydrocarbons, BTEX compounds, phenol compounds and residual biocides and drilling additives.

Using our unique ‘chemical free’ Ti02 catalyst which reacts with the UV light, is used to safely produce a highly oxidative compound species known as Hydroxyl Radicals.  These Hydroxyl Radicals effectively break apart all organic and chemical contaminants into their base components of C02 and H20, allowing flowback water to be treated to a very high standard. 

Whilst Hydroxyl Radicals are an extremely reactive and effective at breaking down trace contaminants and micro pollutants, they feature a very short life, and quickly break down into oxygen and water, posing no environmental risks.

Unlike traditional advanced oxidation techniques that require chemical dosing with hazardous catalytic agents such as hydrogen peroxide or ozone, the Keratox solution provides a fixed and natural catalyst that is not consumed by the process, and therefore has a significant advantage in lowering the operational costs when compared to other technology processes such as membrane filtration.