| The subsurface wastewater infiltration system is suitable for mall-scale municipal wastewater treatment utilizing natural purifying processes. It is a viable option for decentralized wastewater treatment in north-western drought regions of China with its advantages in low cost in investment and energy, and relatively robust efficiency.This paper, based on an experiment conducted in Xi'an, analyzed the performance and mechanism of such a system under various hydraulic loadings. The results are as follows:1. The feasibility was discussed for the local climate and soil conditions.2. Operating the system in the condition of four different hydraulic loading rates, the experiment results showed that the average effluent concentrations of COD, NH4+-N and NO3"-N almost meet the standard for the subsurface wastewater systems. But effluent rate of the total nitrogen far go beyond the standard, and its removal rate is far below. Nitrogen removal mechanics analysis revealed that nitrogen in the influent was mainly eliminated through biological removal via nitrification/denitrification processes, and the bad denitrification led to the low Nitrogen removal rate, thus increased the amount of the total nitrogen effluent.3. The greater the hydraulic loading rate, the lower the removal capacity of COD, NH4+-N and the total nitrogen.4. The system is robust under varying inflow conditions. The temperature and climate had very minor influence.5. The system used a dry-wetness cyclic operating scheme to simulate the municipal wastewater discharging property, which may improved the aeration process.6. The system is efficient in NH4-N removal by converting most of it to NO3-N,which, however, might result in higher NO3-N than recommended value.7. The total nitrogen concentration for high loadings in effluent is above the recommended values due to: high loading, low denitrification ability, and low crop uptake. |
PDF Full Text Request