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Eureka Resources is issued first patent by the United States Patent Office – “Method and System for Treating Wastewater”

Eureka Resources is issued first patent by the United States Patent Office – “Method and System for Treating Wastewater”

The patent issued to Eureka by the USPO specifically represents the treatment processes developed by Eureka to produce a de-wasted water product meeting or exceeding beneficial use criteria, such as the required properties of General Permit WMGR123 (Pennsylvania Department of Environmental Protection, 2012).

FIELD OF THE INVENTION

The present invention relates to methods and systems for processing wastewater. More specifically, the present invention relates to processing wastewater, such as that generated when recovering oil and natural gas, to produce a de-wasted water product meeting or exceeding beneficial use criteria, such as the required properties of General Permit WMGR123 (Pennsylvania Department of Environmental Protection, 2012).

BACKGROUND OF THE INVENTION

Extracting oil and natural gas from unconventional resources, such as shale gas formations, through the combination of horizontal drilling and hydraulic fracturing has increased at a rapid pace in recent years. The Marcellus Shale and Utica Shale are sedimentary formations that underlie most of Pennsylvania and West Virginia and extend into parts of Virginia, Maryland, New York and Ohio. These shale formations are two of several important gas reserves in the United States and together they are one of the largest natural gas “plays” in the world. A “play” is the geographic area underlain by a gas or oil containing geologic formation.

Development of these gas plays and other unconventional resources presents significant potential for economic development and energy independence, but also presents the potential for environmental impacts on land, water and air. For example, between 20% and 40% of the water used for hydro-fracturing a gas well returns to the surface as flowback, and later as produced water. In addition to fracturing fluids added by drillers, this wastewater picks up other contaminants from deep in the Earth.

In some parts of the United States, gas drilling companies typically dispose of wastewater deep in the ground, by using deep injection wells. However, the geology in some locations, such as in Pennsylvania, does not necessarily allow for deep injections. Although municipal treatment plants previously accepted this wastewater, certain states, such as Pennsylvania, prevent water treatment facilities from processes water that has flowed back after fracturing. This restriction is thought to promote the goal of establishing and maintaining a closed loop process for the recycling and reuse of oil and gas liquid wastes. States other than Pennsylvania also restrict the ability of publicly-owned treatment works to accept oil and gas wastewaters.

Recently, a number of states have passed regulations to treat processed wastewater having specific properties as a non-waste product. For example, General Permit WMGR123 (Pennsylvania Department of Environmental Protection, 2012) identifies specific water quality criteria that, if met, will not require wastewater after it is processed to be treated as waste. The specific criteria of WMGR123 are reproduced below in Table 1.

TABLE I General Permit WMGR123 Property Limits Aluminum 0.2 mg/L Ammonia 2 mg/L Arsenic 10 μg/L Barium 2 mg/LBenzene 0.12 μg/L Beryllium 4 μg/L Boron 1.6 mg/L Bromide 0.1 mg/L Butoxyethanol 0.7 mg/L Cadmium 0.16 μg/L Chloride 25 mg/L COD 15 mg/L Chromium 10 μg/L Copper 5 μg/L Ethylene Glycol 13 μg/L Gross Alpha 15 pCi/L Gross Beta1,000 pCi/L Iron 0.3 mg/L Lead 1.3 μg/L Magnesium 10 mg/L Manganese 0.2 mg/L MBAS (Surfactants) 0.5 mg/L Methanol3.5 mg/L Molybdenum 0.21 mg/L Nickel 30 μg/L Nitrite – Nitrate 2 mg/L Nitrogen Oil & Grease ND pH 6.5-8.5 SU Radium-226 + 5 pCi/L Radium-228 Selenium 4.6 μg/L Silver 1.2 μg/L Sodium 25 mg/L Strontium 4.2 mg/L Sulfate 25 mg/L Toluene0.33 mg/L TDS 500 mg/L TSS 45 mg/L Uranium 30 μg/L Zinc 65 μg/L

Accordingly, it is important that public health and the environment are protected as unconventional resource extraction and production activities become a more prominent component of the oil and gas sector. To this end, regulations governing the management of such wastewater have been evolving at the state level, resulting in increased waste management costs for the petroleum industry. Moreover, strict treatment target requirements specified in each state for unrestricted-use water are particularly challenging to meet. Aside from the challenges that may be posed by the regulatory levels for certain contaminants, de-wasting water from oil and natural gas production pose other challenges, including but not limited to the similar density of oil, mud and water; large fluctuation in daily flow rate of the wastewater; and high concentrations of emulsified oil.

There is therefore a need in the art for methods and systems and for processing oil and gas wastewater with a goal to reuse the processed water, such as for water used in well fracturing. It would be especially beneficial if such wastewater could be processed to produce de-wasted water, i.e. unrestricted-use water that is not classified as a “residual waste.” The production of de-wasted water would allow for less burdensome storage, transportation, and reuse or the potential direct discharge of the water keeping it in the hydrologic cycle.

SUMMARY OF THE INVENTION

The present invention is generally directed to methods and systems for treating wastewater, such as wastewater from producing oil and natural gas and primarily directed to a process that employs bacteria and other treatment processes to reduce the levels of contaminants in the wastewater to below regulatory criteria.

In one aspect of the present invention, a method for treating wastewater is provided. The method includes the steps of 1) seeding a pre-anoxic tank with activated sludge comprising micro-organisms; 2) adding distilled water comprising contaminants including nitrogen compounds to the pre-anoxic tank, wherein the distilled water is produced from treated wastewater; 3) denitrifying the nitrogen compounds in the added distilled water in the pre-anoxic tank, wherein the denitrification is performed by the micro-organisms under anoxic conditions; 4) transferring the water from the pre-anoxic tank to an aeration tank; wherein additional nitrogen compounds in the water are nitrified under aerobic conditions wherein the nitrification is performed by the micro-organisms; 5) transferring the water from the aeration tank to a post-anoxic tank; wherein additional nitrogen compounds in the water are denitrified under anoxic conditions wherein the denitrification is performed by the micro-organisms; and 6) transferring the water from the post-anoxic tank to a membrane bioreactor comprising a membrane to remove a portion of the contaminants and micro-organisms from the water to arrive at a purified water from the membrane bioreactor.

In another aspect of the present invention, a system for treating wastewater is provided. The system includes a pre-anoxic tank in fluid communication with a distilled water source and operable to receive distilled water from the distilled water source, where the distilled water is produced from treated wastewater and further wherein the pre-anoxic tank includes activated sludge comprising micro-organisms; an aeration tank in fluid communication with the pre-anoxic tank and operable to receive water treated in the pre-anoxic tank; a post-anoxic tank in fluid communication with the aeration tank and operable to receive water treated in the aeration tank; and a membrane bioreactor including a membrane, in fluid communication with the post-anoxic tank and operable to receive water treated in the post-anoxic tank, where the distilled water includes contaminants such as nitrogen compounds and the nitrogen compounds are denitrified in the pre-anoxic tank and post-anoxic tank and nitrified in the aeration tank; and where the membrane removes a portion of the contaminants and micro-organisms from the water to arrive at a purified water from the membrane bioreactor.

In yet another aspect of the present invention a method for treating wastewater is provided. The method includes the steps of: 1) seeding a pre-anoxic tank with activated sludge comprising micro-organisms; 2) controlling the temperature of distilled water comprising contaminants including nitrogen compounds to a range of between 20° C. to 35° C., wherein the distilled water is produced from treated wastewater; 3) filtering the distilled water to remove a portion of the contaminants; 4) adding the filtered distilled water to the pre-anoxic tank; 5) denitrifying the nitrogen compounds in the added distilled water in the pre-anoxic tank, wherein the denitrification is performed by the micro-organisms under anoxic conditions; 6) transferring the water from the pre-anoxic tank to an aeration tank; wherein additional nitrogen compounds in the water are nitrified under aerobic conditions wherein the nitrification is performed by the micro-organisms; 7) transferring the water from the aeration tank to a post-anoxic tank; wherein additional nitrogen compounds in the water are denitrified under anoxic conditions wherein the denitrification is performed by the micro-organisms; 8) transferring the water from the post-anoxic tank to a membrane bioreactor comprising a membrane to remove a portion of the contaminants and micro-organisms from the water to arrive at a purified water from the membrane bioreactor; and 9) further processing the purified water to satisfy a regulatory criterion.

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