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排序方式: 共有318条查询结果,搜索用时 31 毫秒
271.
Efficient nutrient removal in decentralized wastewater treatment systems is a challenging task. To improve the removal of organic matter and nitrogen from wastewater, two types of bioreactors using membrane-aerated biofilm reactor (MABR) and microbial fuel cell (MFC) techniques were evaluated. During more than 250 days of continuous-flow reactor operation, both reactors showed consistently high chemical oxygen demand removal (>86%). At an influent ammonium-nitrogen (NH4(+)-N) concentration of 30 mg N/L, the average effluent NH4(+)-N concentrations were 6.2 and 0.5 mg N/L for the MABR and MFC reactor, respectively, while the effluent nitrate-nitrogen (NO3(-)-N) concentrations were 5.4 mg/ L in the MABR and 19.2 mg/L in the MFC-based reactor. The overall total inorganic nitrogen removal efficiencies were 64% and 36% for the MABR and MFC reactor, respectively. At the measured dissolved oxygen concentrations of 5.2 and 0.23 mg/L in the aerobic/anoxic zone of the MFC and MABR, respectively, a specific oxygen uptake rate of 0.1 g O2/g VSS-d, resulting from ammonia oxidation, was detected in the settled sludge of the MFC, while no nitrifying activity of the sludge from the MABR was detected. Molecular microbial analysis demonstrated a link between the bacterial community structure and nitrifying activity. The relatively high abundance of Nitrosomonas europaea was associated with its detectable nitrification activity in the settled sludge of the MFC. The results suggest that MABR and MFC techniques have the potential to improve organic and nitrogen removal in decentralized wastewater systems. 相似文献
272.
Thakur Ravindra Singh Kumar Aditya Lugun Onila Ansari Nasreen Ghazi Prasad Satgur Das Triparna Gupta Neha Patel Devendra Kumar 《Environmental science and pollution research international》2023,30(10):25181-25192
Environmental Science and Pollution Research - In recent years, special attention has been given to emission research that led to the deposition of toxicants from road traffic. Thus, it is... 相似文献
273.
Vishwanathan Shalini Laxmi Sree Nandan Sukanya Jayan Shoni Lijo Meghna Das Susmita 《Environmental science and pollution research international》2023,30(4):8448-8463
Environmental Science and Pollution Research - In this study,?~?40 nm anatase TiO2 nanoparticles were successfully prepared by a simple electrochemical method by using succinic... 相似文献
274.
The present research deals with the quantification of health hazard in a fluorosis prone area from east-coast of India. The average health hazard quotients are 2.09, 2.42, 1.79, and 1.69 for infants, children, male, and female adults, respectively. These values are more than the tolerance limit (1) in 92% groundwater samples and 96% of the study area. The children are more vulnerable to fluorosis than infants and adults. Ca2+/ Na+ versus HCO3−/Na+ and Ca2+/Na+ versus Mg2+/Na+ plots suggest silicate weathering as the prime factor while linear relationship of TDS versus NO3− + (Cl−/HCO3−) supports the anthropogenic input of F− to the aquifer system. The study suggests that the F− ions are chiefly derived from fluorite, apatite, biotite, and hornblende present in the granitic basement under alkaline environment. The secondary sources are domestic and industrial sewage as well as return flow from irrigation with ingredients of phosphate fertilizers. The adverse effects of fluorosis can be minimized by mass awareness programmes, alternative source of potable drinking water, defluoridation techniques, dilution of high F− concentration in groundwater, and minimizing the use of phosphate fertilizers. 相似文献
275.
Debasish Guha Thakurata Krishna Chandra Das Arijita Paul Siddhartha Sankar Dhar 《环境质量管理》2023,32(3):69-78
Toxic organic dyes released into aquatic sources as a result of industrial activities pose a significant threat to the environment. The removal of such dyes from water sources is a challenging task in the context of environmental emergencies. In this present effort, the strontium ferrite nanoparticles were synthesized by coprecipitation followed by a calcination method and is applied for photocatalytic degradation of such organic dyes. The ferrite nanoparticles were characterized by FTIR, XRD, VSM, SEM-EDX, TEM, and HR-TEM studies. In the existence of H2O2 under visible light, the catalyst performs efficient degradation of aniline blue (AB) and methyl violet (MV) dyes in a remarkably short interval of time. The superparamagnetic performance of the catalyst was confirmed by VSM, and thus it can be easily recovered from the degraded dye by applying an external magnet. The Fenton mechanism justifies the elevated rate of photo degradation, which generates hydroxyl and perhydroxyl radicals in the progress of the reaction. 相似文献
276.
4-Nonylphenol, a degradation intermediate of commercial surfactant and known endocrine disruptor, has been frequently detected at levels up to several thousand microgl(-1) in surface waters and up to several hundred mgkg(-1) (dry weight) in soil and sediment samples. Large quantities of 4-NP can be quickly sorbed by the organic rich solid phase during wastewater treatment and are concentrated in biosolids, a possible major source for 4-NP in the environment. Microbial transformation in culture studies followed different mechanisms for different 4-NP isomers, which have different estrogenic activity. Composting is a process of solid matrix transformation where biological activity is enhanced by process control. This approach has been used successfully in remediation of contaminated soils and sludges. In this study, the transformation kinetics of 4-NP and its isomers were characterized during biosolids composting. Five distinctive 4-NP isomer groups with structures relative to alpha- and beta-carbons of the alkyl chain were identified in biosolids. Composting biosolids mixed with wood shaving at a dry weight percentage ratio of 43:57 (C:N ratio of 65:1) removed 80% of the total 4-NP within two weeks. At this biosolids/wood shaving ratio (B:WS), the transformation of total 4-NP and its isomers followed second-order kinetic. Higher B:WS ratios yielded significantly slower 4-NP transformation which followed first-order kinetic. Isomers with alpha-methyl-alpha-propyl structure transformed significantly slower than those with less branched tertiary alpha-carbon and those with secondary alpha-carbon, suggesting isomer-specific degradation of 4-NP during biosolids composting. 相似文献
277.
Mahesh Kumar Sahu Ashim Das Gupta 《Journal of the American Water Resources Association》2001,37(3):675-684
ABSTRACT: Operation of a storage‐based reservoir modifies the downstream flow usually to a value higher than that of natural flow in dry season. This could be important for irrigation, water supply, or power production as it is like an additional downstream benefit without any additional investment. This study addresses the operation of two proposed reservoirs and the downstream flow augmentation at an irrigation project located at the outlet of the Gandaki River basin in Nepal. The optimal operating policies of the reservoirs were determined using a Stochastic Dynamic Programming (SDP) model considering the maximization of power production. The modified flows downstream of the reservoirs were simulated by a simulation model using the optimal operating policy (for power maximization) and a synthetic long‐term inflow series. Comparing the existing flow (flow in river without reservoir operation) and the modified flow (flow after reservoir operation) at the irrigation project, the additional amount of flow was calculated. The reliability analysis indicated that the supply of irrigation could be increased by 25 to 100 percent of the existing supply over the dry season (January to April) with a reliability of more than 80 percent. 相似文献
278.
279.
S. M. Das 《Environmental management》1979,3(5):385-386
Conclusions In addition to this natural water-holding capacity of completely forested mountains, development for conservation of water should insure man-made mountain water storage systems, consisting of tanks, ponds, small dams and reservoirs, and artificial lakes at varying altitudes in the Himalayas. An elaborate system of canals would be needed to carry clean water for drinking and cultivation. Alternatively, adjacent highland lakes may be linked up by canals provided with wiers and sluice gates, to carry water to all levels. 相似文献
280.
A study of ground water contamination by arsenic in the residential area of Behala, Calcutta due to industrial pollution 总被引:1,自引:0,他引:1
Due to the discharge of industrial effluent after production of the insecticide Paris-Green [Copper acetoarsenite Cu(CH(3)COO)(2).3Cu(AsO(2))(2)] by a local factory at the P. N. Mitra Lane, Behala, ground water has become contaminated with arsenic. More than seven thousand people were using this arsenic contaminated tube-well water for drinking and house-hold purposes. Many people of the area were hospitalised and symptoms of arsenic toxicity were visible amongst a large number of the population. Analytical study reveals that soil around the area of effluent dumping point, which is at the middle of the locality, contains a very high concentration of arsenic and copper. For the last 20 years this factory had been producing 20 tons of Paris-Green per year and had been dumping its effluent in that area. It seems, the effluent treatment for arsenic removal was not adequate and finally arsenic percolated to the underground aquifers. Consequently, arsenic concentration in the ground water is very high. Both arsenite and arsenate are present in ground water. An alternate source of water other than the ground water is immediately necessary for the people of P. N. Mitra Lane. 相似文献