on january 6, cctvfocus interviewgave a featured report on the protection and treatment of erhai lake in dali and the greening of mountainson east side of lake. as a state-level demonstration project, the dali erhai lake water environment management ppp project undertaken by china water environment group (cweg), provides a perfect solution to plateau lake treatment and ecological industry convergence through the “plateau lake treatment distributed underground wastewater treatment ecosystem” model.

video clip offocus interviewon january 6, 2021

as a vulnerableecological system, erhai lake used to be plagued by environmental problems such as eutrophication. during the “13thfive-year plan” period, cweg proposed an innovative approach to water treatment featuring “plateau lake treatment underground wastewater treatmentecosystem”. the group has built 6 underground wastewater treatment plants, and laid a pipeline network of approximately 231 kilometers to recycle “four waters” (wastewater from kitchen, toilet water, bathing and livestock and poultry farming). the coverage rate of the sewage pipe network and the sewage collection rate and disposal rate have reached 100%.the dali erhai lake water environment management ppp projectproves to be a green ecological barrier for erhai lake, which has laid a solid foundation for green development.

meng jianwei, general manager of cweg yunnan branch

the tailwater treated by the underground wastewater treatment plant would be purified again by ecological pond. the processed water can even reach the class iii surface water standard. “the nitrogen and phosphorus content of the reclaimed water can be used for farmland irrigation. it is really a solution that ‘kills two birds with one stone’”. while realizing resource utilization and zero discharge, the project can spare 20 million tons of sewage discharged to erhai lake annually.5

shuanglang underground wastewater treatment plant

lihuatan ecological pond

meanwhile, the project vacates about 160 mu (around 647,534 m2) of ground space, sparing about 2,000 mu (8,094,177 m2) of land from environmental impact. the supporting facilities above the treatment plant work effectively and efficiently with the erhai ecological corridor. the project also includes a water ecological complex that integrates science education, ecological landscape, leisure and entertainment, and culture to serve the overall tourism development strategy of dali.

wase underground wastewater treatment plant

through years of hard work, the group has basically controlled the water quality of erhai lake and significantly reduced the pollutants discharged into the lake. the transparency of the lake has risen to 1.82 meters on average, reaching a record high in recent years. in 2020, the water quality of the entire erhai lake has reached grade ii for 7 months and grade iii for 5 months. the water quality of no.284 state-controlled section (lakes) is rated as “excellent”. no large-scale cyanobacteria bloom has been found in the past five years.

the submerged vegetation in the lake area has been restored, covering an area of 34 square kilometers. ottelia acuminata, dubbed “touchstone of water quality” blooms again, proving that the erhai lake protection and treatment efforts have achieved significant success.

ottelia acuminata, “touchstone of water quality” in erhai lake

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