No abstract

In order to address the issues regarding the high water content, poor dewatering performance, and occupied space of landfill, the physical property tests and experiments on the lake silt samples were conducted. The effects of cationic polyacrylamide (CPAM), lime dosage, and dehydration time on the dehydration performance indexes such as the concentration ratio, the water content, and the decreasing ratio of water content of the lake silt with the initial water content of 91% were investigated. The results revealed that the concentration ratio reached 3.6 times when the dosage of CPAM was 40mg/L, and the water content decreased to 70% and the decreasing ratio of water content decreased to 29% after dehydration for 10min. The concentration ratio was about 2.6 times when the dosage of lime was 3.8g/L, and the water content decreased to 73% and the decreasing ratio of water content decreased to 24% after dehydration for 10min. The variation laws of water content of the lake silt with initial water content of 91%, 85%, and 80% after flocculation concentration dehydration was studied based on the concept of the decreasing ratio of water content. It was concluded that the decreasing ratio of water content was independent of the initial water content. It was only significantly proportional when the dosage of CPAM was 15∼45mg/L and lime was 1∼7g/L. The linear constant depended on the intrinsic properties of the lake silt. According to the variation laws of the water content and the water-hinge hypothesis, the calculation formula of the water content was proposed and the mechanism of critical addition value breaking the silt hinge in flocculation concentration dehydration was formulated.

Coal mine waters often have high salinity, hardness and alkalinity. The treatment of coal mine water requires careful management of multi-stage reverse osmosis (RO) systems to achieve effective recovery of water for domestic reuse, as well as zero liquid discharge to minimise the impact to the local environment. Design of RO systems for coal mine water treatment has been limited to the use of commercial design packages provided by membrane manufacturers, which do not provide insights into the impact of operating parameters such as feedwater salinity, concentrations of sparingly soluble salts, feed pressure and their interactions with different RO modules on the fouling/scaling potential of RO membranes. This also restricts the use of novel RO products and the delivery of an optimum design based on real needs. In this work, a mathematical model was developed to simulate a standard brackish water RO pressure vessel consisting six full-size RO membrane elements, using computational fluid dynamics (CFD). The model can be used to predict the permeate flowrate, water recovery levels, as well as the spatial information of the accumulation and scaling potential of sparingly soluble salts on the membrane surface. The results obtained from the model showed good agreement with the results obtained from the commercial RO design software WAVE. The CFD model was then used to predict the scaling threshold on various positions of a full-scale RO element, at different operating conditions, using parametric simulations based on Central Composite Designs. Outputs from this work not only provide insights into the microscopic flow characteristics of multiple full-scale elements in the RO pressure vessel, but also predicts the position where scaling would occur, at different feed conditions, for any RO products.

To culture dominant phenol-degrading bacterium for bioaugmentation treatment of coal chemical wastewater, 3 phenol-degrading bacterium such as PDB-1, PDB-2 and PDB-3 were enriched and screened from activated sludge in the coal gasification wastewater treatment plant. The culture conditions such as temperature, pH and additional carbon source were analyzed. At last, the degradation effects of raw water were investigated. Results indicated that PDB-2 was the best bacterial strain with the strongest phenol-degrading ability. The degradation rate was 96.6% in 24 h under the initial phenol concentration of 400mg/L. The degradation rates were respectively 89.5% and 96.1% in 24 h and 36h under the initial phenol concentration of 800mg/L. Under the initial phenol concentration of 400mg/L, the dominant phenol-degrading bacterium grew best with the temperature of 30°C and pH of 7∼7.5, and 100mg/L or 200mg/L addition of glucose could further increase the 24 h degradation rate. When the preprocessed coal gasification wastewater was used to acclimate PDB-2, the total phenol and COD concentration of raw water were 18.2 mg/L and 193 mg/L with the corresponding 48h degradation rate of 95.8% and 92.5%.

According to the water quality characteristics of acid mine drainage (AMD), sulfate removal from simulated AMD by sulfate reducing bacteria (SRB) was improved in a UASB bioreactor. In the meanwhile, the influences of C/S ratio, pH, temperature, and HRT on sulfate removal rate were analyzed to obtain the optimal operation parameters. The results show that under the optimal operation conditions of C/S = 3.0, pH = 6.5, T = 35°C, and HRT = 10 hours, the maximum removal rate of sulfate (86.3%) is reached with an influent sulfate concentration of 2 000 m/L and an effluent sulfate concentration of 274 mg/L which satisfies the local mine drainage discharge standard (500 mg/L). Different from other traditional desalting technologies, the reduction of salinity is realized in this study by removing sulfate from AMD during SRB biodegradation process.