After setting our goal to decompose synthetic dye with laccases, we sought to find out more information of biological sewage treatment and practical problems that required to be addressed. We also wanted to find out how our project could be applied to real world sewage treatment, and what change should we make to improve our project.

Therefore, we visited Hanghua sewage plant（World Trade Center, Beijing, China). Hanghua sewage plant was experienced in using biology method to decompose pollutant while they also had used other ways, including chemical and physical methods. Mr. Li, the manager of the sewage plant, told us lots of information we needed.

During the interview, we found out the situation of each current methods.

First of all, we learned that their previous chemical and physical techniques such as active carbon adsorption and oxidation method, and being expensive in cost for both methods, the sewage plant had to switched to biological treatment.

Hanghua sewage plant mainly used integrated sewage treatment device, in which a critical step was to add bacteria to decompose pollutant. Specially engineered bacteria were able to reproduce rapidly in sewage water, and this allowed the factory to process waste water with relatively lower financial requirement.

However, the bacteria used in sewage treatment may release toxic gases such as H2S. The plant had to turn on the ventilation system periodically, which consumed large amount of electric power and produced loud noise. As time went by, the advantage of lower cost is offsetted by electricity bills and the higher payment for their workers working under unfriendly environment.

In traditional biological treatment method, bacteria are usually injected into waste water directly, floating, growing, as well as continuously being removed by the outflow. The dynamic balance of bacteria concentration might be broken by increasing the total flow of sewage water. Under extreme circumstances, growth rate of bacteria might be overwhelmed by the loss rate through outflow. Moreover, workers in the sewage treatment plant told us, due to wear and tear since 2003 and other undiscovered problems, the total ability of sewage treatment had dropped 40%. To address this issue, we needed to develop a sustainable consumptive material.

By discovering shortcomings of traditional treatment method, we found some critical factors that were worth considering in our project.

The first factor was the low concentration of bacteria/enzyme during treatment. A high flow rate may wash away bacteria fast, lowering the concentration of bacteria/enzymes as well as the chance and duration of contact between pollutant and enzymes. This reminded us to adjust our project in two aspects:
(1) Attach bacteria/Laccase to some fixed matrix, preventing them from being washed away by water flow.
(2) Use lots of small plastic beads to expand surface area, increasing the chance of contact between pollutant and enzymes.

In combination of the two aspects, we may achieve a higher concentration of laccase and longer duration of contact between pollutant and enzymes. Moreover, because the laccase can process the sewage without releasing toxic gas, it will eliminate the unnecessary cost of using extraction pump and extra employee payment, which as a result can enable factory to utilize the biggest advantage of biology method with inexpensive price.

The second factor to consider was the competition among bacteria species. Through human practice, we realized that the composition of sewage disposal was very complicated. There were usually more than one species of microorganism competing in the same environment, which may negatively affect the growth of target bacteria. By allowing our bacteria to produce biofilm, they could get an advantage of growth by sharing nutrients and getting sheltered from competitors.

Finally, we came up with the idea, using PHA plastic beads coated with biofilm and biofilm producing bacteria, then display laccase enzyme on biofilm by adding SpyTag to Biofilm and SpyCatcher to CotA laccase. PHA can also act as a carbon source to bacteria, maintaining growth of bacteria and production of biofilm for longer period. This may further reduce cost by replacing biomaterials less frequently.

In conclusion, through the biology method, we found that the expensive cost and decreasing effectiveness are two main problems for traditional biological treatment method. These experiences from human practice has inspired us with the idea of designing our Biofilm × Laccase system. In the near future, we will build a filter with PHA beads coated with laccase linked biofilm and optimize the filter for real world sewage treatment.

Our public education includes two sections: inner and outer school propaganda. As for on campus part, we design and take a strict but excellent education system by using the resource inside school, and are willing to pass on our system to next generations of IGEMer as a tradition.

As for out of campus part, we establish the collaboration with sewage plant for exchanging the instructive information through biology, plant and policy. It is the only the first step for our team, we strongly believe that the usefulness of our project would attract more plant even business company to cooperate with us.

We conducted lectures about our IGEM project and synthetic biology techniques to students on Tuesday and Thursday weekly. At the start of our education program, during the club exhibition, we briefly introduced our project's purpose, effectiveness and future potential contribution to environment to identify and attract the students who is interested in protecting environment. After that, for the students who as well as have further interests in learning the method of designing something to protect our habitat, we held a series of lectures to explain the specific mechanism, and prove practicability of our project. Furthermore, we taught them about the knowledge of techniques and thinking method we used in designing and finishing the project. In general, our inner-school education program comprehensively passed on our experience as IGEMer and the synthetic biology knowledge as well as triggered their passion of learning synthetic biology and being an IGEMer to think about pollution problems and solutions to retard it.

For the whole process of education, we put a high value on the effectiveness of lecture. Therefore, we required students who is willing to cooperate our work to register their WeChat account, and privately asked randomly 75% of students each time to talk about their experience of it to adjust and improve the content of our lecture for satisfying most of audiences.

Because of the belief in the usefulness of our project and the resolution of protecting habitat, after we visited work leaders of a sewage treatment plant, they established a long-term collaboration to help us conduct the design of our program by providing first-hand information of sewage plant. They intend to know more information of this type of modified biology treatment, and are willing to offer some latest policy to us for having more widely perspective of this project.