Team:Worldshaper-XSHS/Demonstrate
Demonstration and Application Design
1.Azo dye degradation system using for real wastewater treatment
1.1 Dye RR degradation in lab-made and real wastewater
We hope our dye degradation bio-machine system (Part:BBa_K3150002) will eventually apply to the true world. Therefore, based on the positive results from previous experiments, we collected some real wastewater from a local printing and dyeing factory and repeated the experiments of dye degradation under real conditions. Before the operation, we thought carefully and well prepared to avoid any potential risks to ourselves, the community or the environment.
In order to ensure the consistency of the experimental method, we ran the dye degradation experiments for two groups of samples at same time, one was the wastewater from the printing and dyeing factory (shown as “real wastewater” hereinafter) and the other was ddH2O from the lab as what we have used previously (shown as “lab-made wastewater” hereinafter). Both of two groups had been added same concentration of dye RR and same amount bacteria with Part: BBa_K2684000 or Part:BBa_K3150002 for CotA or ScLac producing respectively as the previous experiments. The light absorption value had been recorded in 0 hour, 24 hours, 48 hours and 72 hours.
The results are shown in Fig.1 and Fig.2. The legends CotA(-), CotA(+), ScLac(-) and ScLac(+) in figures represent the control group and experimental group for CotA and ScLac system:
CotA(-): control group, samples with CotA bacteria added but was not induced by ITPG
CotA(+): experimental group, samples with CotA bacteria added and was induced by ITPG
ScLac(-): control group, samples with ScLac bacteria added but was not induced but ITPG
ScLac(+): experimental group, samples with ScLac bacteria added and was induced but ITPG
For the lab-made wastewater group, both CotA and ScLac system showed a good degradation effect on RR. The dye had been degraded and could be observed even by naked eyes at 48 hours and after. Meanwhile, the degradation effect of ScLac system better than that of CotA system in general, however, CotA system seemed to have a better degradation efficiency during the first 24 hours.
For real wastewater group, two laccases worked normally, comparing with the results of lab-made wastewater group, CotA system didn’t showed a better efficiency at any time point. However, two unexpected findings were observed: 1) the degradation effect of the enzyme in real wastewater even faster than that in lab-made samples; 2) the control group which was not induced by IPTG also had obvious decolorization phenomenon. In view of this situation, we suspect that the reason might be the presence of some degradation substances in real wastewater.
1.2 Verification of dye self-degradation in real wastewater
In order to verify the specific cause of this phenomenon, we did the following negative control experiments: adding the wastewater treatment solution WR (i.e. Waterwater + RR) to LB culture medium directly, and taking same concentration dye RR (i.e. ddH2O + RR) into LB culture medium as the control. The results are showed as following (see Fig.3).
It can be seen that the real wastewater without any bacteria added has certain degradation effect, moreover, we observed some mixed-bacteria-like objects in the culture medium after centrifugation. It seemed that there were some bacteria existing in the wastewater which might result a dye degradation effect. In fact, for certain business reasons, the factory didn’t provide any technical details about the wastewater. In order to keep the conditions “real”, we didn’t take a biocidal treatment before the experiments neither.
For time-limit reason, we have no chance to do more experiments on this wastewater samples and the possible self-degradation factors of the wastewater cannot be determined without future research. Whether certain bacteria or other unknown substances, which might result the color degradation, had been added in the factory for wastewater treatment and their working principal need further investigation to determine.
2.Design of an industrial azo dye wastewater treatment system
In order to apply our bio-machine into the real world, we designed an azo dye wastewater treatment system for industrial use in future. A 3D schematic design is shown in Fig.4. Furthermore, we also 3D printed a prototype of the system is shown in Fig. 5. We planned to use this prototype not only as a model of industrial level system for exhibition, but also to test operating principal of the system for demonstration.
2.1 The structure of system
- The uppermost cuboid is the azoreductase reaction cell, the instrument's first degradation process - breaking the azo bond into a slightly toxic aromatic amine compound.
- The second degradation line is the laccase reaction cell (laccase ScLac).
- The third reaction cell is a laccase reaction cell for re-degrading azo wastewater that is not up to the discharge standard.
- Since azoreductase needs to operate normally in an anaerobic environment, we put a strong reducing substance (sodium dithionite solution) into the azoreductase reaction cell to remove oxygen.
2.2 Using steps and working processes of prototype
- 1.Close and tighten all the valves, and fill each reaction tank with the corresponding bacterial liquid.
- 2.Insert 2mmol sodium dithionite solution into the left side of first reaction tank to make an oxygen-free environment.
- 3.Pour the wastewater into the funnel with the fixed water flow rate until the maximum capacity of the first reaction tank is reached.
- 4.Waiting for the wastewater completely entering the first reaction tank then stop the wastewater injection.
- 5.After 48 hours reaction time, open the first valve and let treated wastewater flow into the second reaction tank for another 48 hours reaction.
- 6.Open the second valve and analysis the azo concentration by detector.
- 7.If treaded water was not up to standard, then let water enter the third reaction tank for re-reaction, then repeat step 6 until the water met the standard
- 8.If treated water met the standard, kill the bacteria by UV lamp then discharge the water
3.Advantages
The system has a simple process, which is low cost and easy for use. The prototype will be used for test the principal so as to keep improving the design before a large-scale industrial level system to be built.
It is worth to mention that the 3D printing material using for this prototype is PLA, i.e. polylactic acid, which is a new type of bio-based and renewable biodegradable material made from starch raw materials proposed by renewable plant resources (such as corn, cassava, etc.). It has good biodegradability. After use, it can be completely degraded by microorganisms in nature under certain conditions, and finally produces carbon dioxide and water without polluting the environment. It is a recognized environmentally friendly material.