Study On Polluted River Water Treated By Land Treatment System

Wastewater land treatment system is one of the ecological engineering technologies. The contaminants in the wastewater can be fixed or degraded by land-microorganism-plant system such as farm field, woodland and reed land through biological, chemical or physical progress. Land treatment system can make use of nitrogen and phosphorus in the wastewater to make wastewater stable, harmless and recyclable. So land treatment system is a good method of low cost and low power consumption in treating wastewater. By laboratory experiment and field test, this article mainly studies on the treatment efficiency of typical polluted river water using land treatment system and the variation of concentration of contaminants in the system. The influence of hydraulic load on the system is also analyzed.The main results show that:(1) In laboratory experiment, the change of concentration of contaminant in different depth of soil is complex. When wastewater pours into the model, the concentration of contaminant in different sample point changes a lot. With proper inlet flow, the concentration of contaminant in different sample point has a stable and similar change tendency but has no clear correlation. (2) In laboratory experiment, NH3-N and COD can be greatly degraded in the first part of four models with a removal rate of 80% and 90%. The concentration of outlet TP changes as the concentration of inlet TP varies. The removal rate of TP is from 50% to 80%. (3) In field test, the removal efficiency of contaminant in polluted river water varies with the season and inlet wastewater load. In November, the average removal rate of NH₃-N, COD, NO₃-N in both artificial models is 90%, (50⁷5)% and 50% respectively. The average removal rate of chrominance is over 80% in gravel model and only 35% in plant model. In July, the average removal rate of NH3-N, COD, NO3-N in both artificial models is 50%, (50⁷5)% and (20³0)% respectively. The average removal rate of chrominance is over 80% in gravel model and 50% in plant model. (4) We can summarize from the laboratory and field test that inlet wastewater load can influence the removal efficiency of land treatment system, and its influence on the removal rate of NH₃-N is greater than on that of COD. So if choosing the proper inlet wastewater load, we can use NH3-N as the main design parameter.