Groundwater irrigation induced variations in DOM fluorescence and arsenic mobility.

Dissolved organic matter (DOM) plays a predominant role in groundwater arsenic (As) mobility. However, the temporal-spatial variations in DOM fluorescent characteristics and their effects on As mobility induced by groundwater irrigation remain unclear. To address these issues, groundwater from multilevel and irrigation wells in Zones I and II (with low- and high-As groundwater irrigation, respectively) from the Hetao Basin, China, were monitored in both non-irrigation (NIG) and irrigation (IG) seasons.

[Removal of oil in the lake water in Daqing area using subsurface constructed wetland].

Based on the water quality and climate of the oil contaminated lake in Daqing area, four simulated subsurface wetland systems were constructed in the field to study their removal effect of oil in lake water, including the gravel bed, the gravel-reed bed, the slag-reed bed and the slag bed. The research lasted about 360 d, including five periods: the start up period, the microorganism adding period, the slow-releasing carbon sources adding period, the low temperature period and the normal operation period. During the study, oil removal efficiency of the four units are 24.

[Relationships between loading rates and nitrogen removal effectiveness in subsurface constructed wetlands].

About forty kinds of nitrogen loading removal rate were studied in field in 15 months, inflow and outflow loading rules of reeds/Zizania caduciflora/mixing and no-plant bed were discussed in different inflow loading. The four kinds SFS inflow loading changed from 400 mg x (m2 x d)(-1) to 8 000 mg x (m2d)(-1), while outflow loading is less than 7,000 mg (m2 d)(-1). Results show that outflow loading increase with the increase of inflow loading, linear relation is obvious.

[Effects of plants on nitrogen/phosphorus removal in subsurface constructed wetlands].

Effects of plants on nitrogen/phosphorus removal was studied in pilot-scale in subsurface constructed wetland, the main contents included nutrient uptake, effects of harvesting and roots on hydraulic condition. The result show that the amounts of nitrogen and phosphorous removed by plant harvesting is about 5% of the total removed nutrients in SFS wetlands. The best harvesting periods is between 9-10 month every year.

[Phosphorus removal of agriculture wastewater through subsurface constructed wetland].

Phosphorus removal in subsurface constructed wetland treating agriculture non-pointed wastewater was studied in pilot-scale. The experimental results showed that the removal rates of TP increased with HRT increasing when the nominal hydraulic retention time was less than 5 days. The pH decreased distinctly when the retention time was too longer in the batch and sequence style, it may bring on a lower removel rate of TP.

[Nitrogen removal in a pilot-scale zeolite reed bed system].

In this study, the nitrogen removal efficacy of a pilot-scale zeolite reed bed system was tested for the treatment of agricultural wastewater and domestic wastewater etc. At a mean hydraulic loading of 0.6 m/d, the total nitrogen, ammonia, nitrate, nitrite in winter and spring were reduced across the system by 38.

[Study on nitrogen removal treating agriculture wastewater in subsurface constructed wetland].

Nitrogen removal in subsurface constructed wetland treating agriculture non-pointed wastewater was studied in pilot-scale. The experimental results showed that the removal rates of TN increases with HRT increasing. The removal rates of TN achieved 60% in macrophyte bed system when the nominal hydraulic retention time was 5 days.