I have studied at Guizhou University in China for four years; this period is a very important experience in my life. What impressed me is the comfortable climate in the summer day, air-conditioners or fans are not necessary for the dormitory. Because there is a nature reserve which is called Hua’xi wetland locating just about one kilometer away from the campus. The existing of this wetland regulates regional climate, so in hot days the temperature is lower than the predicted.
A very rare storm occurred in the upstream area makes me realize that the comfortable climate in summer day is not the only benefit the wetland brings to my university. One day morning everyone who lives in the dormitory noticed that the water becomes turbid. Then university office published a notice told us due to the extremely rare storm in the upstream area, the wetland cannot treat dramatically increased water flow, and the simple equipment of water plant of the university also cannot purify the water thoroughly. This is the first time I know that our water for life (not include drinking water) comes from the wetland directly after simple purification and sterilization. Our university extracts water from the wetland to meet our daily demand such as teeth brushing and toilet flushing. Apparently, this wetland meets the standard of water sources area. This wetland saves lots of money for our university to get clean water, since we don’t need to buy clean water from the water company.
This wetland not only can treat the stormwater from upstream area and provide clean water, but also can effectively remove soluble pollutants. Our daily waste water after the solid material being separated out can be discharged into downstream part of the wetland area.
Moreover, more than a thousand different vegetation spices and about five hundred animal species including birds, fish, amphibians etc. live in this wetland area. It provides a pleasant view of a scene and fresh air for the residents and visitors.
What Hua’xi wetland brings to us is not only clean water and reduced expense on waste water treatment, but also a lovely sensual experience.
I believe that the Hua’xi wetland is a good example; it proves a wetland in the urban area can bring both economic, environmental and social benefits. But, in many cities, there is no such naturally formed wetland; thus, constructing wetland is an excellent choice.
The constructed wetland is not a new concept, its application can be traced back to 1903 in Yorkshire, people constructed the first artificial wetland for sewage treatment at Earby. Before this wetland being stopped operation, it is successfully running 89 years (Hiley, 1995). In the 1970s the root zone treatment technology is developed in Germany, and it is proved to be a reliable method to treat waste water (Nanda, 2017).
In the past decade, constructed wetlands in the UK, Germany, France, Australia, Brazil, and the Netherlands have developed rapidly. It has not only become an important waste water treatment measure for small and medium-sized cities, but also has become an important technology for rainwater treatment (Carleton, Grizzard, Godrej, & Post, 2001) and industrial waste water treatment (Vrhovšek, Kukanja, & Bulc, 1996).
The constructed wetland has many economic advantages in treating waste water. Constructing an artificial wetland is cheaper than building a water treatment plant. A study in China shows that we need to invest 100~150 US dollars to acquire 1-ton waste water treatment capacity, but to the same capacity for constructed wetland, the cost is only 25 US dollars (Song, Bi, & Cao, 2003). And for the constructed wetland, labor cost is very limited, if there is no dramatic change in waste water quality and water flow volume, the constructed wetland can automatic running without power plant. But to the traditional waste water plant, both human operation and power consumption are necessary. A good example is in Washington, Indiana. To solve the storm-related sewer overflow, the community needs a more powerful or efficiency waste water treatment measurement. One choice is upgrading the traditional waste water plant which will cost them about $54 million. But, after the firm Bernardin Lochmueller & Associates designed a constructed wetland for the community, the budget for waste water treatment capacity upgrading is nearly halved. Also, the operating cost is saved which is about $1.6 million for each year. In fact, the 27 acres constructed wetland not only just saves money for the local community, but also brings environmental benefit; it is the first time in years that minnows, frog, and other wildlife go back to this area (Casey, 2013).
However, we have to concede that the constructed wetland has some drawbacks. The constructed wetland requires much more land to develop. Compared with the traditional waste water plant, if a constructed wetland wants to have the same treatment capacity, it will need larger land area. Especially in the urban area, the land for construction becomes more valuable with the increase in population.
The time costs is one of the defaults of the constructed wetland. A long lifespan constructed wetland requires a complex system. As we know, the ability of resistance to outside interference depends on the biodiversity of the system; for wetland system, if it has more spices and more complex structure and composition, it will have a more stable system and more anti-interference ability. Then, the constructed wetland can acquire a longer lifespan. But, it asks long time to build a well-developed biodiversity system. The long time to modern people who pursue the high efficiency is not acceptable.
The constructed wetland in some region is not always efficiency, its efficiency changes with seasons. In winter, due to the low temperature, the bioactivity will decline to decrease the wetland waste water treatment efficiency.
To some people, the constructed wetland for treating waste water is not an excellent choice considering its time costs and efficiency issue.
However, money is not the only thing the wetland brings; let’s imagine a scenario:
In a drizzling morning. You are walking along the bank of wetland and breathing the fresh, moist air. And colorful flowers, shining green leaves are on both sides of your path. The stream passes through the cliffs and crosses the bridge, creating turbulence, waterfalls, and flat beaches. You can clearly see the plants on the river bottom; and at distance, you also can see the looming wild birds swimming on the river.
For this scenario, how much do you think it worth?
Carleton, J. N., Grizzard, T. J., Godrej, A. N., & Post, H. E. (2001). Factors affecting the performance of stormwater treatment wetlands. Water Research, 35(6), 1552-1562.
Casey, T. (2013). Meet A Nifty Little Green Sewage Treatment Plant. Retrieved from https://cleantechnica.com/2013/12/07/constructed-wetland-offers-low-cost-wastewater-treatment/
Hiley, P. (1995). The reality of sewage treatment using wetlands. WATER SCIENCE AND TECHNOLOGY, 32(3), 329-338.
Nanda, S. (2017). What is Root Zone Waste Water Treatment? Retrieved from https://www.thehamlet.in/single-post/2017/02/21/What-is-Root-Zone-Waste-Water-Treatment
Song, Z., Bi, X., & Cao, J. (2003). Application of constructed wetlands in sewage treatment in small cities in China. Chinese Journal of Ecology, 22(3), 74-78.
Vrhovšek, D., Kukanja, V., & Bulc, T. (1996). Constructed wetland (CW) for industrial waste water treatment. Water Reseaich, 30(10), 2287-2292.