Ruibin Zhang

Selection of optimal river water quality improvement programs using QUAL2K: A case study of Taihu Lake Basin, China

In recent years, water quality degradation associated with rapid socio-economic development in the Taihu Lake Basin, China, has attracted increasing attention from both the public and the Chinese government. The primary sources of pollution in Taihu Lake are its inflow rivers and their tributaries. Effective water quality improvement programs need to be implemented in these rivers to improve the water quality of Taihu Lake, and to ensure sustainable development in the region. To ensure effectiveness and efficiency, it is important that the optimal water quality improvement program for a specific situation be selected. The aim of this study was to facilitate the selection of this optimal program. The QUAL2K model for river and stream water quality was used to simulate the effects of a range of water quality improvement scenarios in the Hongqi River, which is a polluted tributary in the Taihu Lake Basin. These scenarios consisted of a series of three water treatment technologies in different configurations, from upstream to downstream. The results showed that the optimal scenario comprised a bio-contact oxidation system upstream, followed by an ecological floating bed, and a vertical moveable eco-bed downstream. The reduction rates achieved by this scenario for biochemical oxygen demand (BOD), ammonia nitrogen (NH(3)-N), total nitrogen (TN), and total phosphorus (TP) were 49.50%, 32.81%, 35.94%, and 45.27%, respectively. The QUAL2K model proved to be an effective tool in the comparative evaluation of potential water quality improvement programs. The method applied in this study can prevent the implementation of water quality improvement programs that would not achieve the desired goals.

Simulation of Water Environmental Capacity and Pollution Load Reduction Using QUAL2K for Water Environmental Management

In recent years, water quality degradation associated with rapid socio-economic development in the Taihu Lake Basin, China, has attracted increasing attention from both the public and the Chinese government. The primary sources of pollution in Taihu Lake are its inflow rivers and their tributaries. Effective water environmental management strategies need to be implemented in these rivers to improve the water quality of Taihu Lake, and to ensure sustainable development in the region. The aim of this study was to provide a basis for water environmental management decision-making. In this study, the QUAL2K model for river and stream water quality was applied to predict the water quality and environmental capacity of the Hongqi River, which is a polluted tributary in the Taihu Lake Basin. The model parameters were calibrated by trial and error until the simulated results agreed well with the observed data. The calibrated QUAL2K model was used to calculate the water environmental capacity of the Hongqi River, and the water environmental capacities of CODCr NH3-N, TN, and TP were 17.51 t, 1.52 t, 2.74 t and 0.37 t, respectively. The results showed that the NH3-N, TN, and TP pollution loads of the studied river need to be reduced by 50.96%, 44.11%, and 22.92%, respectively to satisfy the water quality objectives. Thus, additional water pollution control measures are needed to control and reduce the pollution loads in the Hongqi River watershed. The method applied in this study should provide a basis for water environmental management decision-making.

Performance and microbial community analysis of a novel bio-cord carrier during treatment of a polluted river

The performance and microbial community structure of a novel bio-cord carrier during treatment of a polluted river at the laboratory scale was investigated. The bio-cord exhibited good filtration performance, with 87.2% SS removal and an 84.9% reduction in turbidity in 120 min, as well as 19.4-34.4%, 55.2-74.0%, 46.2-55.9% and 13.1-18.5% reductions in the COD, NH3-N, TN and TP, respectively, under three different hydraulic retention times. The bio-cord fibers also provided suitable conditions and support media for microbial growth. Additionally, 114 cloned 16S rDNA sequences were composed of Proteobacteria (57.9%), Bacteroidetes (17.5%) and other phyla (24.6%). There were great differences in bacterial quantity and composition between the surface and inside of the bio-cord. Furthermore, nitrifying and denitrifying bacteria were detected, suggesting that simultaneous nitrification and denitrification processes were occurring. Overall, the results of this study demonstrated that the carrier could attach microorganisms for polluted river treatment.

Calculation of permissible load capacity and establishment of total amount control in the Wujin River Catchment—a tributary of Taihu Lake, China

The deterioration of water quality in Taihu Lake, China, has caused widespread concern in recent years. The primary pollution sources of Taihu Lake are its inflow rivers. Effective environmental water management strategies need to be implemented in these rivers to improve the water quality of Taihu Lake and to promote sustainable development in the region. In this study, the QUAL2K model is used in conjunction with the trial and error approach to assess permissible load capacities for the Wujin River (a major tributary of Taihu Lake) in terms of COD, NH3-N, TN, and TP. Results show that permissible annual loads for these pollutants are 5216.31, 491.71, 948.53, and 104.38 t, respectively. This suggests that COD, NH3-N, TN, and TP loads in the Wujin River catchment need to be reduced by 13.35, 27.26, 47.75, and 37.08 %, respectively, to satisfy national water quality objectives. Total amount control measures are proposed to control and reduce pollution loads of the Wujin River catchment. The method applied in this study should provide a sound basis for water environmental management decision-making.

Spatio-Temporal Distribution Patterns in Environmental Factors, Chlorophyll-a and Microcystins in a Large Shallow Lake, Lake Taihu, China

The spatio-temporal distribution of environmental factors, chlorophyll-a (Chl-a), and microcystins (MCs) in a shallow lake, Lake Taihu (China), were investigated from 2009 to 2011 on a monthly basis at nine sampling stations. The annual mean concentration ranges of total nitrogen (TN), total phosphorus (TP), Chl-a, MC-LR and MC-RR were 0.17–10.53 mg/L, 0.027–0.581 mg/L, 0.10–129.75 µg/L, 0.013–2.019 µg/L and 0.002–0.794 µg/L, respectively. The average TN, ammonium (NH4+) and TP concentrations in Meiliang Bay decreased from 3.54 to 2.26 mg/L, 0.63 to 0.31 mg/L and 0.150 to 0.124 mg/L, respectively, when compared with values from 2006–2008, indicating that water quality has improved in severe cyanobacterial bloom areas in recent years. Additionally, the distribution of MCs was northern lake areas > western lake areas > central lake areas > macrophyte-dominated areas. Correlation analysis revealed that nutrients were the most important variable accounting for the variation of extracellular MC-LR concentration in heavy cyanobacterial bloom areas of Lake Taihu. During the study period, the maximum MCs concentration reached 2.75 ± 0.27 μg/L in the bloom period in the northern lake areas, which is more than two times the safety limit of 1 μg/L MCs required for drinking water. However, microcystins decreased gradually as the water quality improved from 2009 to 2011, indicating that the risk of MCs exposure was slightly decreased in Lake Taihu.

Simulation and Evaluation of Pollution Load Reduction Scenarios for Water Environmental Management: A Case Study of Inflow River of Taihu Lake, China

In the beginning of the 21st century, the deterioration of water quality in Taihu Lake, China, has caused widespread concern. The primary source of pollution in Taihu Lake is river inflows. Effective pollution load reduction scenarios need to be implemented in these rivers in order to improve the water quality of Taihu Lake. It is important to select appropriate pollution load reduction scenarios for achieving particular goals. The aim of this study was to facilitate the selection of appropriate scenarios. The QUAL2K model for river water quality was used to simulate the effects of a range of pollution load reduction scenarios in the Wujin River, which is one of the major inflow rivers of Taihu Lake. The model was calibrated for the year 2010 and validated for the year 2011. Various pollution load reduction scenarios were assessed using an analytic hierarchy process, and increasing rates of evaluation indicators were predicted using the Delphi method. The results showed that control of pollution from the source is the optimal method for pollution prevention and control, and the method of “Treatment after Pollution” has bad environmental, social and ecological effects. The method applied in this study can assist for environmental managers to select suitable pollution load reduction scenarios for achieving various objectives.

Application of QUAL2K Model to Assess Ecological Purification Technology for a Polluted River

Industrialization and urbanization have caused water pollution and ecosystem degradation, especially in urban canals and rivers in China; accordingly, effective water quality improvement programs are needed. In this study, the Tianlai River in Jiangsu, China was taken as a research site, and a combination of ecological purification technologies consisting of biological rope, phytoremediation, and activated carbon were applied in a laboratory-scale study to examine degradation coefficients under dynamic water conditions. Coefficients were then input into the QUAL2K model to simulate various hypothetical scenarios and determine the minimum density of ecological purification combination and hydraulic retention time (HRT) to meet Grade V or IV of the China standard for surface water. The minimum densities for Grade V and IV were 1.6 times and 2 times the experimental density, while the minimum HRTs for Grade V and IV were 2.4 day and 3 day. The results of this study should provide a practical and efficient design method for ecological purification programs.

Application of the QUAL2K model to design an ecological purification scheme for treated effluent of a wastewater treatment plant

Treated effluent from wastewater treatment plants has become an important source of excess nutrients causing eutrophication in water. In this study, an ecological purification method was used to further treat eutrophic water. A three-season ecological purification scheme which comprised an emergent plant (Eme.), a submerged plant (Sub.) and a novel biological rope (Bio.), was designed for the treated effluent canal of a wastewater treatment plant. The removal parameters determined from the experiment were input into a QUAL2K model to simulate downstream water quality of the treated effluent canal. Respective removal rates of total nitrogen and total phosphorus of the Eme., Sub. and Bio. were 32.48-37.33% and 31.63-39.86% in summer, 14.12-33.61% and 17.74-23.80% in autumn, and 14.13-18.03% and 10.05-12.75% in winter, with 1-day reaction time. Optimal combinations for summer, autumn/spring, and winter are Eme. + Bio., Eme. + Bio. + Sub., and Sub. + Bio., respectively. Simulated load reduction rates of total nitrogen and total phosphorus for the treated effluent canal were 42.64-78.40% and 30.98-78.29%, respectively, year round with 2.5-day reaction time. This study provides an efficient evaluation and design method for ecological purification engineering.

The study of venous channel water pollution load reduction technologies

In this paper, Hongqi River of WuJin River watershed (china) was selected as an example, aims to use QUAL2K water quality model simulation water environmental capacity of the Hongqi River, forecasting the pollution load of the Hongqi River basin, and compared to the actual emissions of pollution load, calculated the load reduction rate for satisfying the water quality objectives. At the same time, using QUAL2K simulation different water quality improvement programs contains submerged-type eco-bed technology, bio-contact oxidation technology and ecological floating bed technology, selected optimal program, and calculate the load reduction rate of the river end when implement this optimal program. According to comparison of the load reduction rate for water quality meet the standards and the load reduction rate of the optimal program, proposed effective measures to reduce pollution load of Hongqi River basin. The result shows that environmental management strategies or integrated engineering measures need to be taken to reduce the TN by 23.20% can make the water quality meet the standards. In order to meet the environmental capacity of Hongqi river, effectively improve water environmental quality, presented through source pollution control, non-point source pollution intercept and environmental management measures to reduce the amount of pollutants flow into the river, and with the implementation of load reduction key technologies in the river, together make the Hongqi River water quality meet the standards.

Purification Efficiency of Different Aquatic Plants on Polluted Inflow River of Taihu Lake

Based on building the small aquatic ecosystem in the room, the removal efficiency of total nitrogen (TN) and total phosphorus(TP) in polluted inflow river of Taihu Lake by Cyperus alternifolius(CA), Canna indica(CI), Elodea Canadensis Michx.(ECM) and Ceratophyllum demersum L.(CDL) was researched. The results showed that the removal efficiency of nitrogen and phosphorus in sewage were obvious through these four plants, in which Cyperus alternifolius and Ceratophyllum demersum L. had the better comprehensive purification ability. The order of comprehensive purification ability from strong to weak was: Ceratophyllum demersum L., Cyperus alternifolius, Elodea Canadensis Michx., Canna indica. Research results gave a successful demonstration of ecological treatment to inflow river of Taihu Lake Basin and other similar polluted waters in China.