Adsorption of sediment phosphorus by porous ceramic filter media coated with nano-titanium dioxide film

The porous ceramic filter media (PCFM) was applied to reduce the release of P in lake sediment and we wondered if the nano-TiO2 coating could enhance the P adsorption by PCFM alone in lake sediments. The nano-TiO2 film coated on PCFM in this study was prepared by sol-gel process, and the adsorption properties of sediment Pin all fractions by the nano-TiO2 film coated PCFM were investigated through a series of stirring and static experiments. P release characteristics and various batch sorption conditions, e.g., adsorbent dosage, stirring time, operation temperature and pH were tested, and the kinetics of sediment P adsorption was discussed. The results showed that the sediment released only a small amount of TP within 8 h. The removal efficiency of sediment P in all fractions could reach maximum in 8 h and 22 d under stirring and static experiments, respectively. The residual concentration of Ca-P, Fe/Al-P, IP, OP and TP in the sediment was 85 mg/kg, 255 mg/kg, 310 mg/kg, 95 mg/kg and 431 mg/kg, respectively, and the corresponding removal rate was 19.04%, 44.81%, 43.04%, 45.09% and 44.10%, respectively, under the optimal conditions: adsorbent dosage 4g, operation temperature 30 degrees C and pH 2. The adsorption kinetic models of the sediment P in all fractions could be described well by power function equations (Q(t) = k . t(a), 0 <a <1). The results suggest that the adsorption of sediment P onto the nano-TiO2 film coated PCFM had the great potential to reduce the pollution of internal phosphorus and regulate the transport of sediment P in the aquatic environment. (C) 2014 Elsevier B.V. All rights reserved.The porous ceramic filter media (PCFM) was applied to reduce the release of P in lake sediment and we wondered if the nano-TiO2 coating could enhance the P adsorption by PCFM alone in lake sediments. The nano-TiO2 film coated on PCFM in this study was prepared by sol-gel process, and the adsorption properties of sediment Pin all fractions by the nano-TiO2 film coated PCFM were investigated through a series of stirring and static experiments. P release characteristics and various batch sorption conditions, e.g., adsorbent dosage, stirring time, operation temperature and pH were tested, and the kinetics of sediment P adsorption was discussed. The results showed that the sediment released only a small amount of TP within 8 h. The removal efficiency of sediment P in all fractions could reach maximum in 8 h and 22 d under stirring and static experiments, respectively. The residual concentration of Ca-P, Fe/Al-P, IP, OP and TP in the sediment was 85 mg/kg, 255 mg/kg, 310 mg/kg, 95 mg/kg and 431 mg/kg, respectively, and the corresponding removal rate was 19.04%, 44.81%, 43.04%, 45.09% and 44.10%, respectively, under the optimal conditions: adsorbent dosage 4g, operation temperature 30 degrees C and pH 2. The adsorption kinetic models of the sediment P in all fractions could be described well by power function equations (Q(t) = k . t(a), 0 <a <1). The results suggest that the adsorption of sediment P onto the nano-TiO2 film coated PCFM had the great potential to reduce the pollution of internal phosphorus and regulate the transport of sediment P in the aquatic environment. (C) 2014 Elsevier B.V. All rights reserved

Remediation effect of pond-ditch circulation on rural wastewater in southern China

To mitigate water pollution caused by rapid urbanization in the rural areas of China, it is urgent to develop suitable wastewater treatment technologies, which are socio-economic, environmentally sustainable and easily maintained. This study investigates the remediation effect of a pond-ditch circulation system on water quality. This system is composed of connected ponds and ditches in rural areas. We constructed the treatment systems as follows: system I (S1) was circulated 24 h/day (13.2 L/h), system II (S2) was static with macrophytes, and system III (S3) was circulated with macrophytes. Our results indicated that after 60 days of treatment, the levels of the total nitrogen, total phosphorus, ammonia nitrogen, chemical oxygen demand, chlorophyll a and turbidity of water significantly decreased in the ponds/ditches of S1 and S3. Similar significant decreases of these parameters were observed in the water of the ditch in S2, whereas the concentrations of TN, TP and NH4+-N of water from the two ponds in S2 increased. Moreover, the increase of the species numbers and the diversity index of zooplankton and the decrease of heterotrophic index in three ponds/ditches of S1 and S3 and the ditch of S2 demonstrated the improvement in water quality. The significant relationship between the zooplankton community structure and the environmental variables was confirmed by redundancy analysis (RDA) and Pearson's correlation analysis. In conclusion, the pond-ditch circulation system can effectively remove excessive nutrient loads and improvewater quality and hence represents a simple and economical solution for the restoration of a degraded rural water environment. (C) 2014 Elsevier B.V. All rights reserved

Photocatalytic reduction of phosphorus in the acid pickling milling wastewater from high-phosphorus hematite mineral processing

The photocatalytic reduction of phosphorus in the acid pickling milling wastewater from high-phosphorus hematite mineral processing was innovatively performed in the absence of oxygen and in the presence of hole scavenger under visible light irradiation with Sr-doped TiO2 in the study. Types and ratio of hole scavenger, effect of reduction time, dosage of Sr-doped TiO2 and initial phosphorus concentration on the reduction of phosphorus were investigated. Experimental results indicated that the gaseous product of the photocatalytic reduction was identified to be phosphine. The optimum amount of formic acid and TiO2 were 60 mmol l(-1) and 2.0 g l(-1), respectively, and the phosphorus removal could reach 99.96% when used to treat the actual mineral processing wastewater. The photocatalytic reduction of phosphorus could be described by first order kinetic equation, and the reaction rate was proportional to the concentration of reactants.The photocatalytic reduction of phosphorus in the acid pickling milling wastewater from high-phosphorus hematite mineral processing was innovatively performed in the absence of oxygen and in the presence of hole scavenger under visible light irradiation with Sr-doped TiO2 in the study. Types and ratio of hole scavenger, effect of reduction time, dosage of Sr-doped TiO2 and initial phosphorus concentration on the reduction of phosphorus were investigated. Experimental results indicated that the gaseous product of the photocatalytic reduction was identified to be phosphine. The optimum amount of formic acid and TiO2 were 60 mmol l(-1) and 2.0 g l(-1), respectively, and the phosphorus removal could reach 99.96% when used to treat the actual mineral processing wastewater. The photocatalytic reduction of phosphorus could be described by first order kinetic equation, and the reaction rate was proportional to the concentration of reactants

Phosphorus removal by laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate

This research aimed to investigate the phosphorus (P) removal of a series of laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate in treatment of low concentration domestic sewage. The long-term performance of P removal was firstly studied by using single substrate of anthracite or steel slag, and three systems applying various combined substrates were investigated when the average P loading rate varied between 0.9 and 1.5 g TP/m(2).d. The results demonstrated that both anthracite and steel slag systems were highly effective in removing total P (TP, 77.17 +/- 23.34% and 90.26 +/- 4.48%) and soluble reactive P (SRP, 92.14 +/- 12.56% and 96.20 +/- 2.58%). The system filled with anthracite, vermiculite and steel slag from the top down removed 82.45 +/- 9.52% and 87.83 +/- 8.58% of TP and SRP, respectively. However, other combined substrate systems showed comparative low and fluctuant P removal. The effluent pH was maintained at 7-9, which met environmental requirements of China. Therefore, anthracite provides a long-term high efficiency of P removal and may be a promising substrate from the standpoint of the effluent pH, and the arrangement of combined substrate has a prominent effect on P removal

A COMBINATION PROCESS OF DMBR-IVCW FOR DOMESTIC SEWAGE TREATMENT

A new hybrid system of DMBR-IVCW, which combines a dynamic membrane bioreactor (DMBR) unit and an integrated vertical-flow constructed wetland (IVCW) unit, was applied to treat domestic sewage. The results showed the total removal efficiencies of DMBR-IVCW system at three different operation conditions were 90.3, 93.3 and 92.6% for COD, 93.0, 89.8 and 85.1% for TN, 85.4, 88.0 and 90.4% for TP, and 93.3, 97.3 and 99.1% for turbidity, respectively. The effluent reaches the Class I of National Discharge Standards for sewage in China (GB8978-1996), and can be directly used for water reclamation and reuse. We found that the DMBR unit had good efficiency on removing COD and turbidity, together with great steady performance to buffer organic loadings and hydraulic shocks, while the IVCW unit acted more like an ecological enhanced treatment for the DMBR unit, removing N, P and other nutrients. This hybrid system coupling the advantages of the both units should provide an effective method for high quality effluent.A new hybrid system of DMBR-IVCW, which combines a dynamic membrane bioreactor (DMBR) unit and an integrated vertical-flow constructed wetland (IVCW) unit, was applied to treat domestic sewage. The results showed the total removal efficiencies of DMBR-IVCW system at three different operation conditions were 90.3, 93.3 and 92.6% for COD, 93.0, 89.8 and 85.1% for TN, 85.4, 88.0 and 90.4% for TP, and 93.3, 97.3 and 99.1% for turbidity, respectively. The effluent reaches the Class I of National Discharge Standards for sewage in China (GB8978-1996), and can be directly used for water reclamation and reuse. We found that the DMBR unit had good efficiency on removing COD and turbidity, together with great steady performance to buffer organic loadings and hydraulic shocks, while the IVCW unit acted more like an ecological enhanced treatment for the DMBR unit, removing N, P and other nutrients. This hybrid system coupling the advantages of the both units should provide an effective method for high quality effluent

Application of large-scale integrated vertical-flow constructed wetland in Beijing Olympic forest park: design, operation and performance

This paper deals with the design, purification performance and public questionnaire of the integrated vertical-flow constructed wetland (IVCW) system built in Beijing Olympic Forest Park (BOFP). This IVCW system of 45 000 m2 has been operated to treat reclaimed wastewater and circulated lake water from Aohai lake. The first 6-month monitoring results in 2008 indicated that IVCW showed a statistically significant removal of TP and OP from reclaimed water and the removal of BOD5 from circulated lake water from Aohai lake. The questionnaire of Willingness To Pay (WTP) by visitors to the BOFP showed that 98.1% of the respondents were in favour of the construction of the wetland and approved the performance of IVCW. More importantly, during the periods of Beijing 2008 Olympic Games and Paralympic Games, the IVCW system helped to provide amenable surroundings for sight-seeing athletes and audiences, as well as tourists. The IVCW also helped to embody the concept of Harmony Between Human and Nature, a theme of the Olympics Games. Using IVCW for treating the reclaimed wastewater as recharge provides an innovative, affordable and practical way for northern China to treat municipal wastewaters.This paper deals with the design, purification performance and public questionnaire of the integrated vertical-flow constructed wetland (IVCW) system built in Beijing Olympic Forest Park (BOFP). This IVCW system of 45 000 m2 has been operated to treat reclaimed wastewater and circulated lake water from Aohai lake. The first 6-month monitoring results in 2008 indicated that IVCW showed a statistically significant removal of TP and OP from reclaimed water and the removal of BOD5 from circulated lake water from Aohai lake. The questionnaire of Willingness To Pay (WTP) by visitors to the BOFP showed that 98.1% of the respondents were in favour of the construction of the wetland and approved the performance of IVCW. More importantly, during the periods of Beijing 2008 Olympic Games and Paralympic Games, the IVCW system helped to provide amenable surroundings for sight-seeing athletes and audiences, as well as tourists. The IVCW also helped to embody the concept of Harmony Between Human and Nature, a theme of the Olympics Games. Using IVCW for treating the reclaimed wastewater as recharge provides an innovative, affordable and practical way for northern China to treat municipal wastewaters