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Water Treatment for Biorefinery

Aquatech implements MBBR & MBR to Deliver Low-Cost, Low-Footprint wastewater treatment solution for Nevada Biorefinery

Wastewater plants can greatly reduce your water disposal costs if correctly implemented and operated. While many water treatment manufacturers can proficiently design and build treatment solutions, it is important to understand their O&M (operation & maintenance) capabilities as well. Aquatech is one such company with proven success executing a DBOOM (Design-Build-Own-Operate-Maintain) model for clients across the USA. This outsourcing approach results in tangible long term benefits for plant owners, including sustainable plant performance.

 

A prime example of this success is a biorefinery called Sierra BioFuels Plant in Nevada, where we’ve applied MBBR and MBR in series to serve as a complete wastewater treatment system for our client’s waste streams. In the facility, approximately 200,000 tons of MSW (Municipal Solid Waste) feedstock originally intended for landfill is processed and converted into a low-carbon, renewable jet fuel. At full capacity, this facility will produce more than 10 million gallons per year of renewable F-T syncrude.

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Due to the inherent sustainability focus of the facility, our customer found it very important to limit emissions of all types, including liquid waste streams. For this reason, the local legislation was considering to go with a ZLD (Zero Liquid Discharge) process. But even with ZLD considered, the facility still needed to address two high volume, high COD (Chemical Oxygen Demand) wastewater streams with combined COD of 4,397 mg/L.

 

The chart below shows a basic feedwater analysis for the combined stream. In terms of chemical features, the wastewater consisted of a series of alcohols but was unpredictable in terms of biodegradability. Our first thought based on this information was “Why don't we treat the high strength wastewater with an Anaerobic reactor?”. After all, Aquatech had spent years developing the BioMOD™ EGSB (Anaerobic reactor utilizing an Expanded Granular Sludge Bed), which could remove organic compounds on a wide spectrum of biodegradability and produce reusable biogas to make the process energy-neutral/positive. 

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Using our state-of-the-art testing lab in Milwaukee, we were able to conduct a feasibility study, bench test, and pilot test for the planned anaerobic solution. After testing both and fully investigating any risks associated with this wastewater and we eventually realized that the anaerobic system was able to exceed the COD reduction requirements of the customer. Graph 1 on the following page shows the results of the trial where only the high-COD portion of the influent waste was treated, with COD removal rates reaching up to 98% as HRT (Hydraulic Retention Time) was increased.

 

An aerobic option featuring BioCORE®-based MBBR and Envi-Q®-based MBR was also tested in parallel to further assess the biodegradability of the water. This trial succeeded as well, proving that the wastewater was highly degradable and would be sufficiently treated either way. See Graph 2 for more information.

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Table 1. Anaerobic Pilot Test Results, % COD Reduction vs. Hydraulic Retention Time (hrs.)

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Table 2. Aerobic Pilot Test Results, % COD Reduction vs. Hydraulic Retention Time (hrs.)


Based on these encouraging results, we informed our customer that the deciding factor for them was now total installed cost rather than feasibility. When developing the total installed cost comparison, we found that while an anaerobic system achieved superior COD removal rates, it still would need some downstream filtration before sending to RO (Reverse Osmosis). Another disadvantage was the cost and time associated with hazardous area classification and EPA permitting required for all US anaerobic digestion systems. In contrast, an aerobic scheme was much cheaper, simpler, and required no area classification. But of course, it would have been a multi-step process. After analyzing OpEx and CapEx, it was clear to both us and the customer that aerobic treatment was the superior option.

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Once the aerobic option was chosen, we built out a complete wastewater and ultrapure water treatment system as illustrated in the above block diagram. Overall, we provided the client with our MBBR and MBR systems followed by RO system and FEDI® (Fractional Deionization), which combine to maximize reusable water production at the lowest possible cost and footprint. Using the BioMOD™ philosophy, we were able to simplify transport through standard containers and minimize onsite civil work. In addition, we had the satisfaction of designing an integral portion of one of the world’s most innovative and sustainable energy production facilities.

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Aerial View of Sierra BioFuels Plant. The site is scheduled to begin operating by 2021.

 

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