Description

As the global population rises and water scarcity becomes an increasingly relevant problem, the need for an efficient, cost-effective process of sewage treatment becomes even more pressing.The wastewater treatment plants currently in use are costly and difficult to maintain. Consequently, our team researched ways to improve treatment plant operations so that they are more energy efficient, making them cheaper to maintain.

Although the wastewater treatment process varies by facility, every facility has three main steps: primary, secondary, and tertiary. The primary step removes solid objects such as twigs or trash from water by passing the water through a screen. In the secondary step, bacteria works to break down organic matter. Finally, in the tertiary step, bacteria removes nitrogen and phosphorus to further purify the water. After investigating further into wastewater treatment processes, we saw an opportunity to make the tertiary process more manageable and energy efficient.¹

During the tertiary step of the wastewater treatment process, nutrients such as nitrogen and phosphorus are removed by employing an activated sludge process. Activated sludge contains a multi-culture of bacteria that facilitate the nitrification-denitrification circuit responsible for the removal of ammonia. Some types of bacteria perform a nitrification process while others perform a denitrification process.

We specifically examined a co-culture consisting of Nitrosomonas europaea and Paracoccus denitrificans ² since they are two of the most commonly used species in activated sludge. In this particular co-culture system, Maintaining a consistent level of N. europaea is difficult because P. denitrificans, a facultative anaerobe, can outcompete N. europaea in aerobic environments. A constant fluctuation of the ratio of nitrifiers and denitrifier results from this competition. Additionally, N. europaea cannot thrive in hypoxic conditions. To ensure the maintenance of N. europaea at optimal levels, treatment plants must expend more energy for aeration.

Our solution is to eliminate the need for a co-culture and unite the functions of nitrification and denitrification under a single chassis. We will express nitrification pathway from N. europaea in P. denitrificans. This solution will eliminate the competition in the co-culture, simplifying the management of the bacteria culture. This system will be more energy-efficient due to less oxygenation of the water being required. Our team will perform a reduction of cost analysis for our device as compared to the multi-culture currently being used in wastewater treatment facilities.

Our project involves characterizing several new parts that have never been used in iGEM before. These include a new chassis (P. denitrificans) and two new promoters (Nar and Sod). Additionally, we will be looking into the function of HaoB, a protein associated with HaoA whose function is currently unknown but that is suspected to be important in the nitrification pathway.

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References

1. https://www3.epa.gov/region9/water/recycling/ ↩

2. Uemoto, H., and H. Saiki. “Nitrogen Removal by Tubular Gel Containing Nitrosomonas Europaea and Paracoccus Denitrificans.” Applied and Environmental Microbiology 62, no. 11 (November 1996): 4224–28 ↩