Chapter 4 Water service system design of songhe park
4.5 Water service system wastewater treatment methods
4.5.3 Determination and demonstration of wastewater treatment methods
Songhe park has a 1300m2 viewing pool with moderate water volume and is adjacent to and connected to the river channel with good water storage and drainage conditions. Combined with the conditions, functions and demands of songhe park, the quantity of reclaimed water is not large, the quantity and quality of wastewater sources are stable, and the water quality changes little. Therefore, the wastewater treatment system can establish an ecological treatment system.
In the ecological treatment system, it is mainly divided into artificial wetland technology and oxidation pond. In the park, artificial wetland system is applied more.
Constructed wetland system not only has the strong water treatment ability, but also has the aquatic plant landscape. Since the first artificial wetland was established in Britain in 1903, a number of demonstration projects have been set up around the world, ranging from large lakes to small wetlands in villas and gardens.
Artificial wetland system of effluent water quality can reach the national standard
"surface water environment quality standard" (GB3838-2002)Ⅱ-V class water quality
standard63, according to the plant inside the pool, packing and process of different and different water quality.
In order to prove the artificial wetland can under the condition of pine crane park construction and meet the pine crane park daily water demand, the following list of four typical, effluent water quality conforms to the urban sewage recycling - landscape water quality standard (GB/T 18921-2002) and more artificial wetland cases as pine crane park construction feasibility of artificial wetland construction reference.
He qiang et al.64applied SBR sewage treatment technology and subsurface flow artificial wetland technology to the artificial wetland project in a dormitory area of a university in chongqing for the purification treatment of domestic wastewater and toilet sewage. The constructed wetland area of the project is only 9.3m2, while the sewage treatment capacity is up to 1.5m3/d, and the surface load of the wetland is 0.16m3/m2/ d. The main factor of this value is the advantage of SBR wastewater treatment technology. The SBR reaction pool covers an area of 1m2, with a depth of 1.3m. The combined constructed wetland covers an area of less than 11m2. The success of this project brings enlightenment: the miniature constructed wetland can also have good water quantity and quality.
Ma wei and Cheng Yuanyuan stated that although the high-water yield is mainly caused by the high-water quality of the project, which is mainly caused by rainwater, it also brings some reference value: the pure constructed wetland has high water purification efficiency65.
Yu tongliu et al.66 constructed wetland project in lantian ecological park of honghu lake, hubei province, covering an area of 1440m2, with poor water quality, mainly catering, toilet sewage and other domestic wastewater; After the basic treatment of septic tank, the sewage is discharged to the artificial wetland combined with surface flow and undercurrent, as shown in figure 4.10. The sewage treatment capacity is 40m3/d, and the wetland surface load is 0.028m3/m2/ d. The project proves that the water under the condition of water quality of sewage, after dealing with the basic septic tank,
63 Kang Junli. Feasibility of Constructed Wetland Ecosystem in Urban Wastewater Reuse[J]. Environmental Sanitation Engineering, 2004, 12(2): 114-117.
64 He Qiang, Liang Jianjun, Chai Hongxiang, et al. Experimental study on the treatment of domestic sewage by combined process of SBR and constructed wetland[J]. Construction Science and Technology, 2008(14):16-20.
65 Ma Wei, Cheng RmbRmb. Water reuse technology of constructed wetland in a residential area in Sichuan[J].
Sichuan Environment, 2014, 33(2): 95-97.
66 YU Tong-Li, YANG Ji-Hong, HUA Liu, et al. Demonstration Project of Hotel Sewage Treatment of Hotel Sewage in Scenic Spots[J]. Science and Technology Pioneering Monthly, 2008(4):131-133.
artificial wetland still has the ability to purify the national standard "surface water environment quality standard" (GB3838-2002) in Ⅳ class water quality standards.
Figure 4.10 water purification system of honghu lantian ecological park (source: author)
The area of constructed wetland in Chengdu Living Water Park of Shanghai World Expo is 500 m2 67. As shown in Figure 4.11, by constructing horizontal subsurface flow constructed wetland, the class IV water quality in the Surface Water Environmental Quality Standard (GB3838-2002) can be treated as class III water quality standard with the treatment capacity of 15 m3/d and the wetland surface load of 0.03 m3/m2/d. This project proves that the effluent quality of pure constructed wetland can reach a higher water quality standard.
67 Liu Xuexiang. Constructed Wetland Treatment System of Chengdu Living Water Park in Shanghai World Expo[J]. Shanghai Construction Science & Technology, 2010(6): 62-64.
Figure 4.11 chengdu live water park of Shanghai world expo (Source: http://bbs.zhulong.com/)
The four artificial wetland demonstration project from technology combined with different conditions, such as size, inlet water quality factors proved that artificial wetland effluent water quality can meet the national standards "surface water environment quality standard" (GB3838-2002) in Ⅳ class above water quality standard, even can reach Ⅲ water, artificial wetland system design in the pine crane parks provides practice basis, such as table 4.4.
Table 4.4 main reference data of the constructed wetland demonstration project (author) pproject inflow
water quality
main processin
g technolog
y
constructe d wetland
area
（m2）
main plants
effluent quality
wetland surface
load
（m3/m
2/ d）
handling capacity
（m3/d
）
Dormitor y area of
a university
in Chongqin
g
Domestic wastewater,
toilet sewage
SBR sewage treatment
process and subsurfac
e flow constructe
d wetland
9.3 Windmi ll grass and candied
Canna
Standard for landscape environment
al water quality (GB/T18921
-2002)
0.16 1.5
A district in Sichuan
Rainwater, swimming pool water
Subsurfac e flow constructe
d wetland
16667 reed Standard for landscape environment
al water quality (GB/T18921
-2002)
0.08 1339
Lantian ecologica l park, Honghu,
Hubei
Catering sewage, toilet sewage and
another domestic wastewater
Septic tanks combined
with surface flow and subsurfac e flow constructe
d wetlands
1440 Water bamboo
, reed, cattail
Type IV water quality standards for
surface water environment
al quality standard (GB3838-2002)
0.028 40
Live water park in chengdu, Shanghai world
expo
Low concentrati
on of domestic wastewater,
rainwater
Horizonta l subsurfac
e constructe
d wetland
500 Cattails, reeds, rushes,
etc
Type III water quality standards in the "surface
water environment
al quality standard"
(GB3838-2002)
0.03 15
The viewing pool area of Songhe Park is 1300 m2. If the viewing pool is transformed into a constructed wetland system, the daily sewage treatment of each constructed wetland per square meter in the above four demonstration projects is calculated. The reclaimed water outflow is far more than the daily demand of the park's reclaimed water. According to the surface load of constructed wetland in Chengdu Living Water Park of Shanghai World Expo is 0.03 m3/m2/d, the theoretical reclaimed water discharge from Songhe Park is 39 m3. According to the daily demand of reclaimed water 12.94 m3 in the park, the reclaimed water from the constructed wetland system can fully meet the reclaimed water demand of the park, and the water quality can meet the Class III water quality standard of the Surface Water Environmental Quality Standard (GB3838-2002).