1. Major advantages and technological and economic indices
(1) No need for special land: The entire system is buried underground, so the ground surface can be used as green land, dry land, parking lot, leisure space or sports field, etc.
(2) Small one-time investment: In regard to a system with wastewater handling capacity over 50 tons/day, investment per ton of wastewater amounts to 1,500-1,800 yuan. If no in-depth nitrogen or phosphor treatment is required, the construction cost can be reduced further by 15%.
(3) Low operation cost: The cost for treatment per ton of wastewater is only 0.06-0.08 yuan.
(4) Simple and convenient operation and maintenance: No need for complicated equipment and almost no need for routine maintenance and management.
(5) Satisfactory treatment effects and stable operation performance: Indices like TSS, COD, BOD, ammonium and nitrogen, total nitrogen in the outflowing water from the filtering station after treatment are lower than the limits defined for Grade 1 Class A wastewater as allowed to be discharged from municipal wastewater treatment plants in China (GB18918-2002). The rate of removal of such compositions exceeds 90%, and the rate of removal of total phosphor is 60-95%.
(6) No hazard to the peripheral environment and landscape and no secondary pollution.
(7) Being less subject to climatic impact: The system can be normally operated in North China and in winter conditions.
(8) Occupancy of less land space: The total system occupies a land area of 2.0-2.5 m2/ton (with the ground surface being used as green land or hardened for other uses);
(9) Flexible use: The daily handling capacity for a single system ranges from several tons to several thousands of tons.
In contrast with the conventional wastewater treatment plants (applicable to Grade 1 Class A standard for wastewater discharge), this technology, when used for treatment of 10,000 tons of wastewater, can help to save 10,000 yuan of investment, save 6,000 kW·hours plus electricity, and results in no discharge of sewage. Moreover, the treated wastewater can be easily recovered and recycled. Therefore, the technology proves to be economical, environment-friendly, energy-saving, and water-saving.
2. Demonstration and application
Due to the technological and economic advantages as stated above, this technology has been industrialized and is gradually turning out remarkable economic profits and huge social benefits.
Pilot project in Guangzhou Institute of Geochemistry under Chinese Academy of Sciences (8t/d, June 2005);
Limin Village, Jingjiang City, Jiangsu Province (70t/d);
Shuishan Village, Jingjiang City, Jiangsu Province (70t/d);
Lihua Employees’ Village, Nanzhuang Town, Foshan City, Guangdong Province (200t/d);
Feixiang Village, Xueyanqiao Town, Wujin County, Jiangsu Province (100t/d);
Daxu Village, Nandu Town, Liyang City, Jiangsu Province (2, one 50t/d, the other 30t/d);
Shijie Village, Nandu Town, Liyang City, Jiangsu Province (15t/d);
Shuixi Village, Zhuze Town, Liyang City, Jiangsu Province (25t/d);
Daibu Town, Liyang City, Jiangsu Province (2, one 20t/d, the other 25t/d).
Projects in construction:
Xinjie Village, Xuxiake Town, Jiangyin City, Jiangsu Province (60t/d);
Huahong Village, Zhouzhuang Town, Jiangyin City, Jiangsu Province (50t/d);
Chian Village, Gushan Town, Jiangyin City, Jiangsu Province (20t/d).
Projects to be built:
Ten villages like Xiagang, Ligang, Yuecheng, Gushan, Shengang, Nanzha, etc. in Jiangyin City, Jiangsu Province (20-100t/d each);
Xilai Village, Xilai Town, Jingjiang City, Jiangsu Province (70t/d);
Jinzhu Village, Baini Town, Sanshui District, Foshan City, Guangdong Province (2, 200t/d each, to serve a population of about 3,000);
Shangzaonan Village, Baini Town, Foshan City, Guangdong Province (50t/d);
Shangzaonan Village, Baini Town, Foshan City, Guangdong Province (50t/d).