Yanran Dai

Adsorption characteristics of used brick for phosphorus removal from phosphate solution

Phosphorus is one of the main causes for eutrophication in waterbodies. The techniques for phosphorus removal from wastewater and waterbodies have become a hot topic in the world. In this study, used brick was chosen as an experimental adsorbent for removing phosphorus from phosphate solution, and the effects of brick dosage, pH, temperature and vibration time on phosphorus adsorption characteristics were evaluated. Results showed that phosphorus could be effectively removed using brick powders, and the optimum brick dosages were 4, 9 and 35g/L in the presence of 5, 10 and 50mg/L of phosphorus concentrations, respectively. A significant linear correlation (R-2=0.9904) between phosphorus concentration and optimum brick dosage was observed. The optimum condition was determined to be: brick dosage 20g/L, phosphorus concentration 25mg/L, pH 5, temperature 25 degrees C and vibration time 2h.

Triazophos (TAP) removal in horizontal subsurface flow constructed wetlands (HSCWs) and its accumulation in plants and substrates

Triazophos (TAP) is a widely used phosphorus pesticide in China that possesses a potential risk for water pollution. We have studied the removal efficiency of TAP using pilot-scale horizontal subsurface flow constructed wetlands (HSCWs) as well as the contribution of plants, substrates and other pathways to its removal. For TAP concentrations of 0.12 ± 0.04 mg L−1, 0.79 ± 0.29 mg L−1 and 3.96 ± 1.17 mg L−1, the removal efficiencies were 94.2 ± 3.7%, 97.8 ± 2.9% and 84.0 ± 13.5%, respectively, at a hydraulic loading rate (HLR) of 100 mm d−1; at an HLR of 200 mm d−1, the removal efficiencies were 96.7 ± 1.3%, 96.2 ± 1.7% and 61.7 ± 11.1%, respectively. The isopleth maps of TAP along the direction of flow indicate that most of the TAP removal occurred in the front and middle regions, while the major removal region would move forward with increasing influent TAP. Plant and substrate accumulation accounted for 0.035 ± 0.034% and 4.33 ± 0.43% of the total removal, respectively, indicating that over 95% of the TAP removal was achieved through other mechanisms. Thus, these results suggest HSCWs can be an effective approach with which to treat TAP contaminated water. Furthermore, the longitudinal scale and hydraulic conditions, as well as the roles of plants, substrates and microbes and their interactions, should be further considered in the design and application of CWs for pesticide pollution control.

Nitrate removal from tail water by integrated vertical-flow constructed wetlands at a high hydraulic loading rate

Nitrate removal rates of two pilot-scale integrated vertical-flow constructed wetlands (IVCWs) treating tail water, under a hydraulic loading rate (HLR) of 250 mm/d with a mean influent NO3--N concentration of 24.4 mg.L-1, were evaluated. Mean NO3--N removal efficiencies of 15.5 and 18.5% with mass removal rates of 1.01 g.m(-2).d(-1) and 1.16 g.m(-2).d(-1) for IVCW 1 (planted with Canna indica and Pontederia cordata) and 2 (planted with Typha orientalis and Arundo donax var. versicolor), respectively, were achieved. The removal rate constants as fitted by the first-order area-based model averaged 0.046 and 0.055 m.d(-1), respectively. Since NO3--N was the dominant nitrogen form in the effluent, denitrification was the limiting step in nitrogen removal despite of favorable pH and anaerobic conditions in the wetland beds. Low availability of carbon source, high HLR, and low temperature could be the probable influencing factors for the observed low NO3--N removal efficiencies. However, IVCW could be used to treat tail water for nitrate removal at a comparable high loading rate.

Seasonal variation of microbial community for the treatment of tail water in constructed wetland

Effects of seasons and hydraulic loading rates (HLR) on the treatment performance and the response of the microbial community of vertical flow constructed wetland treating tail water were investigated. The seasonal treatment performance was evaluated at four HLR of 125, 250, 375 and 500 mm/d, respectively. The microbial community was detected by MiSeq Illumina platform at HLR 125 and 375 mm/d. The wetland showed significantly higher chemical oxygen demand (COD) and total nitrogen (TN), total phosphorus (TP) at HLR 125 mm/d, compared with other HLR. Overall removal efficiency was 61.47%, 71.40% and 76.31% for COD, TN and TP, respectively, while no significant differences for COD, TN and TP removal were found at HLR of 250, 375 and 500 mm/d. The best removal efficiency for COD and TN was achieved in summer and autumn, while the best TP removal was achieved in winter. Nitrification bacteria (Nitrosomonas and Nitrospira) were significantly higher in HLR 125 mm/d, whereas sequences associated with denitrification had no significant difference at the two HLR. The results can partially explain the significantly higher NH4+-N removal in HLR 125 mm/d and relatively low nitrogen performance in winter.

Remediation effects of used brick powder on nutrient-laden sediment

AbstractSediment is one of the major sources of internal pollution in lakes. Pollution control of contaminated sediment has become a hot topic in the world. In this paper, used brick powder was chosen as a passivator for remediating nutrient-laden sediment, and the relationships between brick powder dosages and pollutant indexes in the overlying water and sediments were determined. The results showed that in the overlying water, brick powder could be used to reduce total phosphorus (TP) concentrations; however, it had no effects on total nitrogen (TN), chemical oxygen demands, pH, and oxygen. In the sediments, organic matter (OM), TN, TP, Fe–P, Al–P, and Ca–P concentrations were decreased, while organic phosphorus (Org-P) was increased. Using principal component analysis, it was found that brick dosage could significantly affect the sediment physicochemical properties. A positive correlation was established between brick dosage and Org-P, and a negative correlation with TP and organic matter. An optimal d...