Submerged macrophyte Ceratophyllum demersum affects phosphorus exchange at the sediment-water interface

Substantial research efforts were made to assess the effects of submerged macrophytes on water quality improvement, but information on the mechanism of submerged macrophytes relative to the exchange of phosphorus (P) at the sediment-water interface is very limited. To help fill the void, a popular species, Ceratophyllum demersum L. was chosen to address the effects and mechanisms of submerged macrophyte growth on the processes of P exchange across the sediment-water interface. In treatment mesocosms (planted), equilibrium phosphorus concentration (EPC0) value falls from 68.4 to 36.0 mu g/L, with a mean value of 52.5 mu g/L. Conversely, the distribution coefficient (Kd) value has a predominantly increasing trend. But they are both significantly higher than an unplanted control (p < 0.05). Also, in the planted mesocosm, maximum phosphate sorption capacity (Q(max)) was significantly reduced (4,721-3,845 mg/kg), and most of the linear correlations between different forms of phosphorus and sediment P adsorption parameters were affected (p < 0.05). The EPC0 Percentage Saturation percentages (EPCsat) in planted groups were 325% higher than that in control (p < 0.05). We conclude that C. demersum could promote the release of P from sediments, and soluble reactive phosphorus concentration in overlying water is probably the driving force for P exchange at the sediment-water interface

Effects of the submerged macrophyte Ceratophyllum demersum L. on restoration of a eutrophic waterbody and its optimal coverage

In the paper, submerged macrophyte Ceratophyllum demersum L was selected, and four simulation systems at 0, 20%, 33% and 50% restoration coverage (COV) were used to evaluate the purification effects of submerged macrophytes on restoration of a nutrient-polluted waterbody. The results showed that the water quality was improved significantly in the presence of C. demersum L Specifically, turbidity and concentrations of TP, NH4+-N, Chl.a were reduced by more than 60%. PCA and Pearson's correlation analysis indicated a significant negative correlation between their reductions and COV of the C. demersum L. (P<0.05). ANOVAs and PCCA showed no significant differences among groups with different COV of C demersum L Based on comprehensive consideration, 20% is probably the optimal restoration coverage area for C. demersum L in eutrophic shallow lakes. (C) 2011 Elsevier B.V. All rights reserved.In the paper, submerged macrophyte Ceratophyllum demersum L was selected, and four simulation systems at 0, 20%, 33% and 50% restoration coverage (COV) were used to evaluate the purification effects of submerged macrophytes on restoration of a nutrient-polluted waterbody. The results showed that the water quality was improved significantly in the presence of C. demersum L Specifically, turbidity and concentrations of TP, NH4+-N, Chl.a were reduced by more than 60%. PCA and Pearson's correlation analysis indicated a significant negative correlation between their reductions and COV of the C. demersum L. (P<0.05). ANOVAs and PCCA showed no significant differences among groups with different COV of C demersum L Based on comprehensive consideration, 20% is probably the optimal restoration coverage area for C. demersum L in eutrophic shallow lakes. (C) 2011 Elsevier B.V. All rights reserved

Effects of Ceratophyllum demersum L. restoration on phosphorus balance at water-sediment interface

The effects of submerged macrophytes Ceratophyllum demersum L. restoration on different forms of phosphorus in overlying water, pore water and sediments were investigated under indoor condition, and the correlations between environment variables were also analyzed. The results showed that the concentrations of total phosphorous (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) in the overlying water were reduced by 73.21%, 83.78%, 70.04% and 71.94%, respectively. The effects on TOP and SRP in pore water were not significant and no effect was observed for TP and PP. However, the TP release rate from the sediment was significantly enhanced (p = 0.008), along with the increase of decomposition rates of organic phosphorous (OP) (p < 0.001) and the NH4Cl-P release rate (p < 0.001). No significant differences for BD-P, NaOH-rP, HCl-P between the experimental system and control were found in the sediment. (C) 2012 Elsevier B.V. All rights reserved.The effects of submerged macrophytes Ceratophyllum demersum L. restoration on different forms of phosphorus in overlying water, pore water and sediments were investigated under indoor condition, and the correlations between environment variables were also analyzed. The results showed that the concentrations of total phosphorous (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) in the overlying water were reduced by 73.21%, 83.78%, 70.04% and 71.94%, respectively. The effects on TOP and SRP in pore water were not significant and no effect was observed for TP and PP. However, the TP release rate from the sediment was significantly enhanced (p = 0.008), along with the increase of decomposition rates of organic phosphorous (OP) (p < 0.001) and the NH4Cl-P release rate (p < 0.001). No significant differences for BD-P, NaOH-rP, HCl-P between the experimental system and control were found in the sediment. (C) 2012 Elsevier B.V. All rights reserved

Purification efficiencies and microbial community structure of integrated vertical-flow constructed wetland for domestic wastewater treatment during acclimation period

Two parallel pilot-scale integrated vertical-flow constructed wetland systems (IVCWs) were employed to study the removal efficiencies for domestic wastewater and changes of microbial community structure during acclimation period. The results indicated that the acclimation period for common pollutants removal was 40 days. The mean removal rates during acclimation period were achieved for COD (77.02%), TN (57.21%), NH4+-N (45.63%) and TP (67.78%), respectively. Fatty acid methyl esters (FAME) analysis and function groups PCA analysis demonstrated the microorganism community structure during the acclimation period realized stable after 90 days' operation. Based on the results of purification effects and microbial community structure, 90 days was probably optimal acclimatization period for IVCW system under this experimental condition.Two parallel pilot-scale integrated vertical-flow constructed wetland systems (IVCWs) were employed to study the removal efficiencies for domestic wastewater and changes of microbial community structure during acclimation period. The results indicated that the acclimation period for common pollutants removal was 40 days. The mean removal rates during acclimation period were achieved for COD (77.02%), TN (57.21%), NH4+-N (45.63%) and TP (67.78%), respectively. Fatty acid methyl esters (FAME) analysis and function groups PCA analysis demonstrated the microorganism community structure during the acclimation period realized stable after 90 days' operation. Based on the results of purification effects and microbial community structure, 90 days was probably optimal acclimatization period for IVCW system under this experimental condition

Comparative evaluations of organic matters and nitrogen removal capacities of integrated vertical-flow constructed wetlands: Domestic and nitrified wastewater treatment

Two groups of integrated vertical-flow constructed wetland (IVCW) microcosms were established for treating two types of representative wastewater: domestic and nitrified wastewater under two loading rates (LRs) over about two years. Their removal capacities of organic substance and nitrogen as well as the effects of loading rate (LR), outflow temperature and dissolved oxygen (DO) concentration were investigated and compared. Efficient chemical oxygen demand (COD) eliminations were achieved by the IVCWs, with the mass removal rates increasing linearly with the increasing LRs strongly, achieving average value of 56.07g m(-2) d(-1) at the highest loading rate. Nevertheless, the effluent COD concentrations also increased, with the average value exceeding Class I A discharge standard (< 50mg L-1) for municipal wastewater treatment plants in China at the highest loading rate. Greater total nitrogen (TN) mass removal rates but lower efficiencies were obtained at the high LR for both types of wastewater, and better removal was achieved for nitrified wastewater (NW) in comparison to domestic wastewater (DW), probably due to the prevailing anoxic conditions inside the IVCW beds restricted nitrification process of DW. The influences of LR, temperature and DO on COD removal were slight, but all remarkable on TN reduction. As compared to DO, temperature was more crucial for nitrogen removal, and the temperature dependence coefficient for TN removal of low LR of NW was significantly greater than others

Treatment performance and microorganism community structure of integrated vertical-flow constructed wetland plots for domestic wastewater

In order to investigate the treatment performance and microorganism mechanism of IVCW for domestic wastewater in central of China, two parallel pilot-scale IVCW systems were built to evaluate purification efficiencies, microbial community structure and enzyme activities. The results showed that mean removal efficiencies were 81.03 % for COD, 51.66 % for total nitrogen (TN), 42.50 % for NH4 (+)-N, and 68.01 % for TP. Significant positive correlations between nitrate reductase activities and TN and NH4 (+)-N removal efficiencies, along with a significant correlation between substrate enzyme activity and operation time, were observed. Redundancy analysis demonstrated gram-negative bacteria were mainly responsible for urease and phosphatase activities, and also played a major role in dehydrogenase and nitrate reductase activities. Meanwhile, anaerobic bacteria, gram-negative bacteria, and saturated FA groups, gram-positive bacteria exhibited good correlations with the removal of COD (p = 0.388), N (p = 0.236), and TP (p = 0.074), respectively. The IVCW system can be used to treat domestic wastewater effectively.In order to investigate the treatment performance and microorganism mechanism of IVCW for domestic wastewater in central of China, two parallel pilot-scale IVCW systems were built to evaluate purification efficiencies, microbial community structure and enzyme activities. The results showed that mean removal efficiencies were 81.03 % for COD, 51.66 % for total nitrogen (TN), 42.50 % for NH4 (+)-N, and 68.01 % for TP. Significant positive correlations between nitrate reductase activities and TN and NH4 (+)-N removal efficiencies, along with a significant correlation between substrate enzyme activity and operation time, were observed. Redundancy analysis demonstrated gram-negative bacteria were mainly responsible for urease and phosphatase activities, and also played a major role in dehydrogenase and nitrate reductase activities. Meanwhile, anaerobic bacteria, gram-negative bacteria, and saturated FA groups, gram-positive bacteria exhibited good correlations with the removal of COD (p = 0.388), N (p = 0.236), and TP (p = 0.074), respectively. The IVCW system can be used to treat domestic wastewater effectively

Treatment performance of integrated vertical-flow constructed wetland plots for domestic wastewater

Two pilot-scale integrated vertical-flow constructed wetlands (IVCWs) in parallel were employed to evaluate domestic wastewater treatment performance at a loading rate of 250 mm/d, and each was planted with two different plant species: Typha orientalis and Arundo donax var. versicolor (Plot 1), and Canna indica and Pontederia cordata (Plot 2). The results showed that different plant combinations offered no significant improvement in pollutant removal efficiencies (p > 0.05). The mean removal efficiencies associated with Plot 1 and Plot 2 were 59.9% vs. 62.8% for COD, 15.0% vs. 12.8% for TN, and 52.0% vs. 51.1% for TP, respectively. The mean mass removal rates (g m(-2) d(-1)) were 44.3 vs. 46.4 for COD, 1.27 vs. 1.08 for TN, and 0.393 vs. 0.386 for TP, respectively. It was noted that nitrification was the limited step for TN removal. Dissolved oxygen (DO) in the wetland beds was a dependence factor for the removals of organic matter and nitrogen, and it could be used to predict removal rates of chemical oxygen demand (COD) and total nitrogen (TN). Low temperatures had a negative impact on nutrient removals, especially for TN. (C) 2012 Elsevier B.V. All rights reserved.Two pilot-scale integrated vertical-flow constructed wetlands (IVCWs) in parallel were employed to evaluate domestic wastewater treatment performance at a loading rate of 250 mm/d, and each was planted with two different plant species: Typha orientalis and Arundo donax var. versicolor (Plot 1), and Canna indica and Pontederia cordata (Plot 2). The results showed that different plant combinations offered no significant improvement in pollutant removal efficiencies (p > 0.05). The mean removal efficiencies associated with Plot 1 and Plot 2 were 59.9% vs. 62.8% for COD, 15.0% vs. 12.8% for TN, and 52.0% vs. 51.1% for TP, respectively. The mean mass removal rates (g m(-2) d(-1)) were 44.3 vs. 46.4 for COD, 1.27 vs. 1.08 for TN, and 0.393 vs. 0.386 for TP, respectively. It was noted that nitrification was the limited step for TN removal. Dissolved oxygen (DO) in the wetland beds was a dependence factor for the removals of organic matter and nitrogen, and it could be used to predict removal rates of chemical oxygen demand (COD) and total nitrogen (TN). Low temperatures had a negative impact on nutrient removals, especially for TN. (C) 2012 Elsevier B.V. All rights reserved

Removal efficiency and balance of nitrogen in a recirculating aquaculture system integrated with constructed wetlands

The nitrogen (N) balance for aquaculture is an important aspect, especially in China, and it is attributed to the eutrophication in many freshwater bodies. In recent years, constructed wetlands (CWs) have been widely used in wastewater treatment and ecosystem restoration. A recirculating aquaculture system (RAS) consisting of CWs and 4 fish ponds was set up in Wuhan, China. Channel catfish (Ictalurus punctatus) fingerlings were fed for satiation daily for 168 days with 2 diets containing 5.49 % and 6.53 % nitrogen, respectively. The objectives of this study were to investigate the N budget in the RAS, and try to find out the feasibility of controlling N accumulation in the fish pond. It is expected that the study can provide a mass balance for the fate of N in the eco-friendly treatment system to avoid eutrophication. The results showed that the removal rates of ammonia (NH+4-N), sum of nitrate nitrite (NO-X-N), and total nitrogen (TN) by the CWs were 20-55%, 38-84 % and 39-57 %, respectively. Denitrification in the CWs was the main pathway of nitrogen loss (41.67 %). Nitrogen accumulation in pond water and sediment accounted for 3.39 % and 12.65 % of total nitrogen loss, respectively. The nitrogen removal efficiency and budget showed that the CW could be used to control excessive nitrogen accumulation in fish ponds. From the viewpoint of the nitrogen pollution control, the RAS combined with the constructed wetland can be applied to ensure the sustainable development for aquaculture