保护工人阶级利益
Protect the interests of the working class
单级人工湿地
single stage constructed wetland
低阶人工内容
labor content lower levels
化工工人
Chemical industry workers
Chemical plant workers
Employees of chemical factory
trace element
人工工作量模型
artificial work-load model
人工级配骨料
artificially graded aggregate
人工人口系统
artificial population systems
三级人工湿地
Three-stage Constructed Wetland