Applied Mechanics and Materials Vols. 90-93

Abstract: A cost combined life cycle environmental assessment was carried out to estimate the economic and environmental impact of wastewater treatment in the pulp production site of China. Results showed that the impact seen from abiotic depletion, acidification, eutrophication, global warming, fresh water aquatic ecotoxicity, and marine aquatic ecotoxicity categories represented an important contribution to the overall environmental impact, while the impact seen from human toxicity, terrestrial ecotoxicity, and photochemical oxidation categories played relatively small role. Specifically, the machine, electricity, coagulant production processes had the highest contribution to the overall environmental and economic impact. Improving electricity and chemicals applications efficiency are the efficient way to minimize overall environmental and economic impacts.

Abstract: Aiming at the water quality characteristics of low turbidity and low temperature of the Reservoir Water derived from Yellow River(RWDFYR), the technology of micro-flocculation direct filtration for RWDFYR was studied. The effluent index such as COD_Mn, UV₂₅₄, TOC and turbidity was investigated under the different filtration rate conditions of 4m/h, 5m/h, 6m/h, 8m/h and 10m/h. The results show that the value of removal efficiency of turbidity reached at 98%, and the value of removal efficiency of organic matter was 40% also. In this study, the removal effect was good under the filtration rate of 6m/h. Moreover, the removal effect of different filter layers was also carried out. Finally, it concluded that the backwashing cycle of filter layer should not exceed 3days.

Abstract: The simultaneous removal of carbon and nitrogen of the anaerobically pretreated distillery wastewater with nitrate, nitrite and ammonia addition was investigated in an expanded granule sludge bed (EGSB) reactor inoculated with methanogenic granule sludge. The experiment showed the COD removal efficiency decreased with the nitrogen loading increasing. Moreover, denitrifiers out-compete methanogens for the utilization of organics gradually, and COD removed by methanogenesis decreased to only 20% by measuring the amount of CH4 produced at low C/N ratios of 2, 3 and 4. Nitrate reduction to ammonium didn’t occur whatever the C/N ratio under anaerobic conditions. At high C/N ratios of 10 and 8, little total Kjeldahl nitrogen (TKN) was removed. However, 30%-50% of TKN entering the reactor was removed at lower C/N ratios of 2, 3 and 4 suggesting the removal of ammonium. At a lower C/N ratio of 2, the nitrite and the nitrate accumulation were observed and TKN removal decreased gradually due to their inhibition. The result suggested that the nitrate and ammonium simultaneous removal occurred through a coupling of nitrate reduction to nitrite by denitrification and then nitrite reduction to nitrogen gas by both denitrification and Anammox at a proper C/N ratio in an anaerobic EGSB reactor.

Abstract: Dewatering characteristics of aerobic granular sludge, activated sludge and sludge which mixed flocculant was studied. It was shown that the specific resistance of aerobic granular sludge is lower than activated sludge and sludge with mixed flocculant was in the range of 1.07~1.80×10⁹ S₂/g, and it increased with the increase of diameters of the granules. The water ratio of aerobic granular sludge by pressure filtrate dehydration was decreased to 83.5~86.1%, activated sludge and sludge which mixed flocculant were 94.2% and 91.4%, respectively. The structural characteristics, distribution features of extracellular polymeric substances and PN/PS values of aerobic granular sludge were important factors of its excellent dewaterability. Aerobic granular sludge technology was regarded as one of the promising biotechnologies in sludge treatment.

Abstract: coking tail wastewater is difficult to dispose due to its hard-degradation substance. Biological Aerated Filter (BAF),with a characteristics of strong resistance to organic impact load,is a new way in treating high-concentration organic wastewater.In this paper, coking tail wastewater disposed in two-stage BAF is investigated. It shows that the optimized condition to dispose organic is that temperature is 25 ~ 35 °C, pH is7 ~8, gas-water ratio is 2~3:1, reflux ratio is 0.5~1. Under optimal conditions COD removal rate of the system remains stable around 69.10%.

Abstract: According to the situation of Chinese urban water supply, this article has analyszed the possibility and computing method for water hammer that caused by pump stop in large diameter and high-lift water pipelines. In addition the impact of Full-featured Pump Curve on the water hammer calculation are also discussed. Finally, using the water hammer calculation of the primary pumping stations within a water-supply project which located in northeast China as an example, we had made corresponding conclusion.

Abstract: The nitrite accumulation in Biological Aerated Filter (BAF) treating simulated municipal wastewater was investigated and the possibility of nitrous nitrification in low ammonia wastewater treatment was discussed. The results indicate that the lower concentration of DO was of advantage to the formation of the nitrite accumulation. When the concentration of DO was controlled to less than 0.5 mg/L, the nitrite accumulation rate can improved significantly to the maximum over 80%. By adjusting pH, nitrite accumulation can take place in BAF. When the influent pH value was 6.5 to 7, the highest nitrite accumulation rate was 57%. But long-term stable nitrite accumulation cannot be obtained only through changing influent pH value. The increasing of hydraulic loading can contribute to nitrite accumulation. When the hydraulic loading was enhanced to 10 m³/(m²•h) , the average nitrite accumulation rate can be increased by 52.5 times. When concentration of DO was 1.0 to 1.5, influent pH was 6.5 to 7 and the filtration rate was 5 m/h, the nitrite accumulation of BAF reactor was of good stability. During 60 days’ running, the nitrite accumulation rate can keep at 65% to 75% stably and obvious nitrous nitrification was found.

Abstract: Biological Aerated Filter (BAF) has been global applied in secondary and tertiary wastewater treatment process in the past decades. As the increasing application of BAF, it was required to get deeper understanding of the operational discipline, parameter optimization and structural characteristics of BAF to improve the treatment efficiency and to operate stability constantly. In this paper, a physical filtration equation of clean filter bed was established firstly based on an average porosity ratio equation and Kozeny-Carman filtration equation. And then the influence of biological oxidation and biofilm development were introduced, of which the Eckenfelder mode and oxygen transfer were considered, to induce a hybrid physical- biologically equation to describe the headloss development in the BAF.

Abstract: A seed crystal medium was developed from the powder steel slag and other material in order to carry out a novel method for phosphorus removal and recovery through the crystallization process. Continuous-flow fixed-bed column experiment was conducted to investigate the phosphorus removal capacity with low P concentration (10mg/L), and the influences of HRT, Ca/P ratio and pH on the treatment efficiency were also considered. It was observed that the P concentration of filter effluent was always lower than 0.5mg/L whether under the experimental condition of pH=7 and HRT=60 min or the condition of pH=7, HRT=30min and the Ca/P ratio = 1.5. With the HRT 30min, increasing pH to 7.5 and decreasing Ca/P ratio to 1, the P concentration of filter effluent was still lower than 0.5mg/L. The XRD analysis of the sediment obtained from the filter bed proved that product formed in the phosphorus removal process was Hydroxyapatite (HAP), illustrated that the crystallization occurred in the process of P-removal. The results of this study suggest that the fixed bed - phosphorus crystallization process with seed crystal media is a promising technique for phosphorus removal and recovery.

Abstract: In order to evaluate the feasibility of the hybrid physical– biologically filtration equation of Biological Aerated Filter (BAF) developed previously, the parameters of the filtration equations were determined through the numerical simulation and experimental fitting, and the empirical formula was carried out finally. The results showed that experimental data were in agreement with the simulated data very well, illustrated that the determined parameter was reasonable and the equation can be used to forecast the headloss development of the tested filter.