Sea Water Restoration

This year, we were very close with Najing iGEM team. Their project is working on heavy metal removing through biofilms. When we talked about collaboration, we first thought about binding two projects on seawater desalination field. Thus, we discussed an application with this two project combing. Our team is responsible for explain this application and its supporting fact. Nanjing Team will explain the details which needs to be discuss to make this working for real. On this page, we will share the final discussion report.

Brackground information

Most of the seawater desalination plant use open-water intake near coastal to avoid intake costs. This also means that the factories can’t avoid to deal with different pollution in coastal seawater, including heavy metal pollution.

The main source of coastal heavy metal pollution is runoff and atmospheric sedimentation.

From 2006 to 2007, Oceanic Administration People’s Republic of China did a massive-scale offshore detection for water condition. In its report, the concentration of lead, copper, zinc and mercury in seawater which is over the first seawater class at some monitoring spots. (Yunlong,2011) Among them, average lead concentration in the Bohai Sea is over the first seawater class, and some of the monitoring spot detect a number over the second seawater class.

The nature degradation of heavy metal is very difficult. Also, the offshore is relatively big water body which makes the pollution hard to increase as well as decrease. Overall, the heavy metal pollution of Chinese offshore cannot be overlook when we use seawater as material.

Also, we have to introduce the Nanjing project. Their idea is a novel bio reactor design that can both adsorb heavy metal pollutants as well as respectively retrieve precious heavy metals.They choose some of the representative heavy metal, lead, gold,and uranium as tier primary target.

Seawater circulating restoration

In normal desalination process, even normal resource water has to go through some sedimentation processes. In fact, one of the safety concern of general seawater desalination is what do we do with those sediments. The idea of cooperating two project is to achieve a new seawater recovery and utilizing system.

Seawater should not be seen only as an source water. It is also a important component of ecosystem and potential resource of mineral and other chemical substance. In this report, we focus on how the merging will help to reduce pollution and repairing the original ecosystem.

Heavy metal cycle in sea

The word “circular economy” should be familiar to most people. In China, this is one of the guiding ideology for the economic and society development. The core of the concept is to maintain the balance between resource and waste. To balance the rapid consumption of resource, man should not only depend on nature but also ourselves to turn wastes into resources.

Unlike water has a strong nature balance itself, heavy-metal’s nature circulation is much slower (Qi et al, 2010). We need to use man power to turn every waste kind into resource. In this concept, seawater desalination combing heavy-metal recycling will be the key to build the heavy metal’s balance.

Previous heavy metal recovery

The origin of heavy metal comes from the river, therefore, it is hard to control from the origin. Most of the study dealing with heavy metal in seawater focus on recovery and has to work in an open condition (Xia et al, 2005). The efficiency of absorption largely depends on the mobility of seawater. It also brings some safety concern by introducing new species to original ecosystem.

For example, the main recovery method focuses on mangrove in China. Mangrove is salt-torrent and absorb heavy-metal naturally(Zheng et al, 1993). Mangrove will help build a great ecosystem for animals and other plants. Yet, this will never be the original one anymore. Furthermore, because it is plant, the study and application of mangrove will be relatively slow.

Our purpose

Thus, we want to build a recovery system with three criteria:

The heavy metal recovery should be quick process and recyclable.
Using existing relatively flowing cycle of seawater.
Every elements can be improved and study quickly.

Of course, NJU project satisfied the first criteria. For the second requirement, seawater desalination is one of the few seawater alternating technology that pumps in seawater. It also has complicated process, and part of it could be replaced by Nanjing’s project. Over all, this will increase the force that heavy-metal waste change into resource with a low cost adding.

Location selection

The location selection is extremely important for this system.There's some elements should be considered:

Cell-tolerance
Heavy metal concentration (enough to damage its ecosystem)
Other chemicals

We also need to reconsider the original desalination intake choice,and build a new intake water quality grading system.

However, with limiting time, we can only lay out these idea. Right now, through our discussion,estuaries is a strong candidate with a severe heavy metal pollution and unique ecosystem that we want to reserved.

However, this a place between sea and river, which means it will have a mixed feature might not be the best desalination intake. In the other word, this feature might be conflict with the place which requires seawater desalination.Thus, this needs to be further discussed

Conclusion

This collaboration study might not provide actual data support. It is to provide a possibility for two mostly different project to work together. Hopefully, we can be the first to introduce and discuss a flowing seawater recovery system. And eventually,this idea will solve some real-life problems.

Reference

Qi L I U, Hua-ke W, Wen-da L I. The ecological effect and global chemical recycle of the heavy metal lead [J][J]. Journal of Anhui Institute of Education, 2010, 23(6): 97-100.

XIA L, ZHANG H, JIAN J, et al. Study on the application of phytoremediation technology to the treatment of wastewater in the coastal sea [J][J]. Water Resources Protection, 2005, 1: 010.

Yunlong, H. (2011). Study of Major Environmental Problems in offshore China (Doctoral dissertation, Third Institute of Oceanography, State Oceanic Administration).

Zheng, F., Lin, P., & Zheng, W. (1993). Study on the tolerance of Kandelia candel mangrove seedlings to cadmium. Acta Ecologica Sinica, 14(4), 408-414.

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Team:SJTU-BioX-Shanghai/Human Practice/Restoration