Demonstration study of bypass stabilization pond system in the treatment of eutrophic water body.

This study involved a comprehensive renovation of fish ponds to improve the water quality of a eutrophic river in Dongguan City. The abandoned fish ponds were transformed into three different types of stabilization ponds: facultative, aerated biological, and submerged plant stabilization ponds. The water of the eutrophic section of the river was pumped into the facultative stabilization pond and discharged into the Haizai River through an aerated biological pond and a submerged plant pond. In the aerated biological pond, secondary treatment was carried out using plant zoning and artificial floating island aeration system. The submerged plant pond used fountain-type aeration and an underwater forest for tertiary treatment. After four months of monitoring the water quality of the stabilization pond and the river, the ammonia nitrogen (NH3-N), total phosphorus (TP), and chemical oxygen demand (CODCr) levels in the raw sewage reduced from 6.53 mg/L to 1.13 mg/L, 1.76 mg/L to 0.29 mg/L, and 63 mg/L to 22 mg/L, respectively; the transparency of water increased to 45 cm, and dissolved oxygen (DO) level increased to 5.32 mg/L. This study provides a reference for the ex-situ treatment of urban eutrophic waterbodies.

Case study of the in-situ restoration of black-odorous water by combined process of forced aeration and biological contact oxidation.

Black and odorous water bodies are an extreme phenomenon that impair ecological integrity, adversely affect the lives of residents and the town's image, and cause unpleasant sensory experiences. Herein, we consider a black and smelly river in Heshan City, Guangdong Province, as a case study. The proposed comprehensive governance process combines the use of pollution control and interception, sediment remediation, aeration oxygenation, a high-efficiency biological contact oxidation/denitrification pond, and ecosystem construction. The project operation results showed that the combined process can effectively improve water quality. The water quality of the river improved to the Class V standard. All indicators met the requirements of the 'China Surface Water Environmental Quality Standard' (GB3838-2002). River water quality indicators, monitored for four months, revealed that water transparency and dissolved oxygen increased by 5.9 times and 24.5 times, respectively. Dichromate index (CODcr), total phosphorus (TP), and ammonia nitrogen (NH3-N) were reduced by 5.8, 4.17, and 5.17 times when compared to the values observed before treatment. The black-odor and eutrophication of the river were successfully eliminated, and the water quality improved significantly. In general, the combined process exhibits a high technical feasibility for implementation, providing a specific reference value for the treatment of black and odorous water bodies in urban settings.

Demonstration study of bypass multipond wetland system to enhance river water quality.

This study focused on the water quality of a river in Wuhan City, China, which is surrounded by ponds that were transformed into a bypass multipond wetland system to improve river water quality. The bypass multipond wetland system included surface-flow artificial wetlands, modified partition ponds, aeration reoxygenation ponds, ecological ponds, and other processes. After the stable operation of the process, the water transparency was higher than 60 cm and the dissolved oxygen (DO) was higher than 5 mg/L, while the ammonia nitrogen (NH3-N) concentration was less than 1.0 mg/L, total phosphorus (TP) was lower than 0.2 mg/L, and chemical oxygen demand (COD) was lower than 20 mg/L, achieving the treatment target. After monitoring the results of each process, the process which best enhanced the water transparency enhancement was the surface-flow of the artificial wetlands and ecological ponds. The aeration reoxygenation pond had the best effect on DO enhancement. The processes that most affected NH3-N and TP removal were the surface-flow artificial wetlands and ecological ponds. The modified parthenogenic pond had the greatest effect on COD removal. The bypass multipond wetland system not only improved the river water quality but also enhanced the river landscape, and can act as a reference for similar river water quality improvement actions.

Preparation and application of embedded and immobilized Achromobacter sp. agent for effective removal of ammonia nitrogen from water.

A novel wastewater-quality-improver, Sodium Alginate Embedded Microbe-treated Zeolite (SAEMZ), was proposed. The strains used are screened from black-odorous water and have high-efficiency NH4+-N degradation performance. The Gram-positive bacteria, belonging to Achromobacter sp., was determined through the screening and identification for this strain, whose removal rate of NH4+-N can reach 88.06%, to decrease the NH4+-N concentration from 61.83 mg/L to 7.80 mg/L, and its optimal growth conditions are pH 7-8, rotation speed 150-210 r/min, temperature 25-35 °C. The SAEMZ's removal effect on NH4+-N was considered in this research from aspects of reusability, storage stability, and the effects of dosage, coexisting ions, and wastewater's concentration. The increase of the SAEMZ's dosage effectively improved the NH4+-N removal rate; Ca2+ in the solution promoted the NH4+-N removal rate, while Mg2+ and Mn2+ inhibited it. Also, the NH4+-N removal rate improved slightly with Fe2+ concentration's increase and then decreased significantly; with the increase of the wastewater dilution factor, the NH4+-N removal rate showed an upward trend and with the increase of the SAEMZ's reuse times, it decreased. Therefore, recycle times should be controlled to less than 3 times in practical application; the SAEMZ still maintains its physiological stability, high mechanical strength, and good storage stability after being stored at 4 °C for 120 days.

Research and application of arsenic-contaminated groundwater remediation by manganese ore permeable reactive barrier.

Arsenic pollution in the water environment is one of the important environmental problems at present. High arsenic groundwater and its resulting local arsenic poisoning have caused a great threat to human life and health. The permeable reactive barrier (PRB) is an underground in-situ remediation technology, which has the advantages of high efficiency, low energy consumption, long aging, low operating and maintenance costs. By studying the arsenic removal effects of different materials, this paper selected natural manganese ore, manganese ore granulation, loaded manganese ore and mixed manganese ore as fillers for PRB. And it conducted a simulated experiment to study the feasibility of actual PRB engineering to repair arsenic-containing groundwater. The experiment proves that the removal rate of arsenic by four manganese ore materials exceeds 90%. After examining the geographical location and hydrogeological conditions of the PRB project, the Dengjiatang area of Chenzhou City, Hunan Province was selected as the construction area. Studies show that after the completion of PRB, the arsenic content of the effluent at each monitoring point is below 10 µg/L. It indicates that all four fillers achieve the purpose of removing arsenic, and can be applied to the project according to actual needs. Finally, the safety evaluation of the PRB project was carried out. And FeCl3·6H2O was selected as the base curing material and cement was as the process auxiliary stabilizer to solidify the arsenic-containing waste residue. The arsenic concentration in the leaching solution of the arsenic slag after curing is only 1 µg/L.