The De Nora blog: Water Made Easy

What are Mobile Treatment Units (MTU's) and how do they work?

Sep 1, 2020 9:30:00 AM / by De Nora

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Mobile Treatment Units for disinfection of produced water in the Oil & Gas industry

Mobile Treatment Units (MTU's) are the safest and most effective oil field water treatment solution on the market today. A MTU is a self-contained system for the on-site generation of sodiium hypochlorite, an effective oxidizer that can be used to disinfect water used in hydraulic fracturing operations and do the heavy lifting in recycling produced water. MTU's are build in  standard C-containers, which are air-conditioned for a safer and more comfortable working environment, and the system comes with all of the equipment needed to generate and inject sodium hypochlorite as well as the testing equipment needed to monitor water treatment operations.

Using sodium hypochlorite is an exceptionally safe and environmentally-friendly solution, it is biodegradable and does not create hazardous chemicals or explosive gasses. The sodium hypochlorite generated by the MTU's is compatible with friction reducers as demonstrated by pressure pumping service providers who have completed extensive loop testing. 

Safety

Unlike industrial strength sodium hypochlorite, a widely used disinfectant in produced water treatment, a 0.8% hypochlorite solution is not caustic and requires minimal precautions when handling. Sodium hypochlorite has a negligible effect on pH and leaves only 1-2 ppm of residual free available chlorine when properly applied.

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How a Mobile Treatment Unit disinfects water

De Nora's MTU's use the ClorTec® electrochlorination system to generate an aqueous solution of 0.8% sodium hypochlorite. We use the sodium hypochlorite as a biocide for disinfecting frac water, removing H2S, and oxidizing iron. Operationally, pumps (that are 100% redundant) bring  freshwater into the MTU where it is filtered, softened, and pumped into a salt tank to produce a brine. The brine solution is then diluted with freshwater and passes over electrically-charged titanium electrodes in the ClorTec® unit to to create a sodium hypochlorite solution, which is then pumped into a 400-gallon reserve tank. Pumps (that are 100% redundant) then pump the solution into a manifold for “on the fly” treatment of frac water or the first-stage oxidation treatment of produced water.

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Before initiating the treatment of the produced water, it’s essential to perform laboratory analysis of water. This data determines the optimal process to treat the water and meet the customer’s water quality specifications, using the simplest and most cost-effective method. Typically, the process consists of injecting a 0.8% sodium hypochlorite into the water to oxidize H2S and iron. Once the iron has been oxidized, the produced water flows through clarifying tanks to settle the residual floc and finally a sand filter for "polishing" to complete the process.

Frac-on-the-fly water disinfection

Frac water treatment consists of providing biocide and other chemicals, such as scale inhibitors, required to properly condition the water before it's injected downhole. Neptune, De Nora's on-site service provider, supplies MTU''s and operators, to enable operation 24 hours a day, 7 days a week. 

During the frac operation, Neptune checks Adenosine Triphosphate concentrations in the working tanks every 20 minutes to ensure that no bacteria goes downhole. After completing the frac, Neptune will also test the flow-back water for the presence of acid-producing bacteria (APB) and sulfate-reducing bacteria (SRB) at 30, 60, and 90 day intervals to ensure there are no bacterial problems downhole. 

Proven Technology

For over 25 years, municipal water treatment facilities all over the world have been using on-site hypochlorite generation to purify the drinking water of over 500 million people. De Nora's MTU's feature the ClorTec® patented electrochlorination system, a proven technology for treating frac water, De Nora, and their service provider, Neptune has earned a reputation as the most technologically-advanced water treatment company for the Upstream and Midstream Oil & Gas Industry.

How much sodium hypochlorite? 

Compute the proper level of sodium hypochlorite based on water quality with our FREE online dosing calculator. Click below for more information.

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Tags: onshore, oil and gas

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