Three-Phase Ammonia Air Scrubber Recycles Water

EPA Grant Number: SU836779
Title: Three-Phase Ammonia Air Scrubber Recycles Water
Investigators: Barsanti, Kelly
Institution: University of California - Riverside
EPA Project Officer: Sergeant, Anne
Phase: I
Project Period: September 1, 2016 through August 31, 2017
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text |  Recipients Lists
Research Category: Sustainability , P3 Awards , P3 Challenge Area - Water

Description:

Design a three-phase water-based ammonia air-scrubbing and filtration system for concentrated animal feeding operations (CAFOs) that promotes sustainability by reusing water, recycling waste and reducing farmers’ costs.

Objective:

Modern farms use chemical scrubbers to reduce ammonia emissions. These scrubbers use significant amounts of water, as the scrubbers are flushed continuously to avoid clogging. Our primary sustainability challenge will be to reduce the water consumption from 25 m3/hr. of use without compromising performance. Our secondary sustainability challenge is to maximize the separation efficiency of ammonia from both the initial air (feed gas) and flushing water stream. We propose a three-phase water-based ammonia air-scrubbing and filtration system that promotes sustainability by reusing water, recycling waste, and reducing costs. While ammonia emissions from agricultural sources remain a significant concern for air quality, the current conventional chemical scrubbers do not represent a sustainable solution, as they have high economic and environmental costs. The capital cost for a single unit can reach up to $13,776 with an additional $9,694/year for operation and maintenance (Zhao, Hadlocon, and Manuzon). Water scrubbers exist and do not use sulfuric acid, but are less efficient; plus, a continual stream of water is required, adding economic and environmental costs. Our innovative three-phase design builds on these current systems. Phase one uses a water-based air-scrubbing (gas absorbing) unit. Phase two uses a novel clinoptilolite filter to collect ammonium from the waste stream, cleaning the water for reuse. This second phase eliminates the requirement for waste disposal of the water-ammonia effluent. Phase three uses an air stripper to further reduce the ammonia concentration from the water. The water can now be used to complete the cycle again. In this project we will build and test our three-phase water-based ammonia air-scrubber system, which has great potential for reducing economic and environmental costs. 

Approach:

Concentrated animal feeding operations (CAFOs) must meet air quality safety standards in order to maintain a safe environment for animals and workers, as well as surrounding communities. CAFO enclosures use large fans to draw out particulate matter and gas-phase pollutants (e.g., methane and ammonia).The air is pulled through a scrubbing system that typically incorporates either a chemical (sulfuric acid) or water scrubber to absorb or convert the pollutants into a manageable form. Our three-phase design uses a water scrubber in phase 1, similarly to current designs, but with implementation of water recycling. In phase 2, a natural zeolite ion exchanger (clinoptilolite) with a high affinity and selectivity for ammonium ions provides a cost­ effective and re-useable filter that separates the effluent into water (that is recycled) and ammonium  ions (that are collected). The effluent stream no longer requires waste disposal, but instead supplies water for reuse and the waste ammonium can be used to create fertilizer. In phase 3, a fresh air feed is utilized to strip any remaining ammonia from the water; the recycled water and any stripped ammonia return to phase 1 where the continuous cycle proceeds. This innovative design maintains improved air quality for human health while providing a sustainable approach to water usage, benefitting people and all living forms on the planet. At the current price of $1,100 per acre-foot, a typical system using a continuous water stream of 25m3/hr. would cost nearly $200,000/year (Vekshin). The high cost of operation hurts farmers' pocketbooks, but there are also high costs for the environment. In a 2015 Executive Order, Governor Brown proclaims that a State of Emergency exists in California due to ""severe drought conditions"" (Executive Department State of California). California doesn't have water to waste, so the three-phase system design addresses this need to conserve water. The design also is cost-effective to make end-users more prosperous while improving the environment. Presentations on our work will be given to promote sustainability. An upcoming event hosted by the Society of Women Engineers (SWE) will give the team an opportunity to engage local high school students (see letter). Presentations and prototype demonstrations will be held at Engineers without Borders (EWB) meetings to inspire their members to be solution oriented in their approach to design (see letter).

Expected Results:

The outputs of this project will be a sustainable three-phase water-based ammonia air­ scrubber system that meets air quality needs and complies with statewide mandates to cut water usage, by reducing generated waste and overall costs. On-site ammonia emissions will be reduced on average by 70%, with 59.5% removed from the air and kept from waste disposal by using the ammonium as fertilizer. The introduction of this three-phase air-scrubbing system will implement water recycling to significantly reduce the 25 m3 water/hr. used in the current systems. With four consecutive years of drought, water conservation efforts are imperative in California. In May, 2015, ABC Channel 7 news reports that ''the Inland Empire, Riverside County had to do as much as 25 to 30 percent" in water reduction to keep up with mandates (Juarez). Outcomes of this project include: less air pollution due to ammonia and less ammonia containing waste effluent; less money spent on water treatment because less water will be used; and less money lost due to devalued areas based on lack of water supplies.

Supplemental Keywords:

Ammonia mitigation, water conservation, gas absorber, ion exchange, water purification, ammonia stripper, livestock housing facilities, zeolite mineral filtration, agricultural runoff pollution, extrapolation;