A neighborhood search algorithm was proposed to simultaneously schedule the waste removal quantity and the equipment fleet profile over the mine life for open pit mines. An initial search domain was ...first defined and a good schedule was obtained as the current best schedule by searching in this domain. Then, progressively narrower neighborhood search domains were constructed around the current best schedule to search for better schedules. The objective is to minimize the present value of waste removal costs over the mine life. The resulting schedule from this algorithm provides a complete fleet profile for each year over the mine life: the selected equipment models, the number of equipment units of each model, the age of each unit, as well as the quantity of waste removed. A numerical example of application was provided to demonstrate the feasibility and merits of the algorithm.
An operational study for the removal of hazardous waste (phenol and resorcinol) in aqueous system was achieved using white laccase purified by polyethylene glycol (PEG)-salt, aqueous-two-phase-system ...(ATPS). To explore the phase formation various molecular weight and concentration of PEG, types and concentration of salts were optimized using One Factor at a Time (OFAT). Four salts (NH4)2SO4, Na2SO4, K2HPO4, (NH4)2PO4 were selected on the basis of phase formation. ATPS recovered white laccase in saline phase PEG (10%) 8000, Na2SO4(30%) had specific activity (SA) and purification factor (PF) of 3.6 U mg−1 and 2.5-fold. The recovered laccase successfully removed hazardous waste (1 to 10 mM) at different enzyme loads i.e., 0.67 and 1.34 U mL−1 after 12 h of incubation. At 0.67 U mL−1 load phenol and resorcinol was completely removed (5 mM), whereas 1.34 U mL−1 completely removed resorcinol and 86% phenol (10 mM) after 12 h.
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•Successfully removed hazardous wastes by ATPS recovered white laccase.•Single step recovery of white laccase using PEG–salt ATPS system.•Operational system for enzymatic removal of phenol and resorcinol in aqueous system.
•Hydrolysis of sodium toluene sulfonate (STS) in sub-/supercritical water was investigated.•Supercritical water oxidation was used for total removal of STS from wastewater.•The optimum condition is ...T=452°C, water and CO2 flow rate of 2.3 and 0.08mLmin−1, respectively.•Hydrolysis of STS increases with the increase in temperature and CO2 flow rate.
The hydrolysis of sodium toluene sulfonate (STS) in sub-/supercritical water in the presence of CO2 was investigated using a continuous flow system at the constant pressure of 250bar. The effect of water flow-rates, reaction temperature and CO2 flow-rates on the hydrolysis of STS was investigated. Results showed that hydrolysis of STS increases with the increase in temperature and CO2 flow rate. The optimum reaction conditions calculated by partial factorial design were 452°C, water flow rate of 2.3mLmin−1 and CO2 flow rate of 0.08mLmin−1. Furthermore, supercritical water was used for total removal of STS from industrial wastewater using H2O2 as an oxidant. Results showed that at temperatures higher than 350°C more than 99% of STS is oxidized while COD remains high until reaction temperature of 450°C after which COD of solution diminished 81%.
The abundance and relevance of Accumulibacter phosphatis (presumed to be polyphosphate-accumulating organisms PAOs), Competibacter phosphatis (presumed to be glycogen-accumulating organisms GAOs), ...and tetrad-forming organisms (TFOs) to phosphorus removal performance at six full-scale enhanced biological phosphorus removal (EBPR) wastewater treatment plants were investigated. Coexistence of various levels of candidate PAOs and GAOs were found at these facilities. Accumulibacter were found to be 5 to 20% of the total bacterial population, and Competibacter were 0 to 20% of the total bacteria population. The TFO abundance varied from nondetectable to dominant. Anaerobic phosphorus (P) release to acetate uptake ratios (P rel /HAc up ) obtained from bench tests were correlated positively with the abundance ratio of Accumulibacter/(Competibacter + TFOs) and negatively with the abundance of (Competibacter + TFOs) for all plants except one, suggesting the relevance of these candidate organisms to EBPR processes. However, effluent phosphorus concentration, amount of phosphorus removed, and process stability in an EBPR system were not directly related to high PAO abundance or mutually exclusive with a high GAO fraction. The plant that had the lowest average effluent phosphorus and highest stability rating had the lowest P rel /HAc up and the most TFOs. Evaluation of full-scale EBPR performance data indicated that low effluent phosphorus concentration and high process stability are positively correlated with the influent readily biodegradable chemical oxygen demand-to-phosphorus ratio. A system-level carbon-distribution-based conceptual model is proposed for capturing the dynamic competition between PAOs and GAOs and their effect on an EBPR process, and the results from this study seem to support the model hypothesis.
Effluents from aquaculture facilities must be effectively managed to remove dissolved wastes and suspended solids that can pollute receiving bodies of water. High volume, dilute flows leaving ...settling or filtration units can appear pristine, but still contain dissolved wastes. Effective technologies are needed to treat high volume effluents from intensive fish farms. The objective of this study was to evaluate fluidized sand biofilters as a treatment option for removing carbonaceous biochemical oxygen demand (cBOD5), total-ammonia-nitrogen (TAN), total phosphorous, total suspended solids (TSS), and total coliform bacteria from high volume intensive aquaculture effluents. Treatment across three full-scale CycloBio® fluidized sand biofilters was evaluated using two sand sizes, i.e., an effective size (D10) of 0.11-mm and 0.19-mm sand that were each expanded approximately 60% at a superficial velocity of 0.31cm/s and 0.64cm/s, respectively. Two bed management techniques were also evaluated: (1) siphoning from the top portion of the bed and (2) a biofilm shearing method in which a submersible pump was used to strip and release excess biofilm as it accumulated at the top of the expanded bed. Greater removal of cBOD5, TAN, and nitrite, and greater dissolved oxygen consumption across the biofilter correlated with the 0.11-mm sand. Additionally, improvements in removal of cBOD5, TAN, and nitrite, and greater dissolved oxygen consumption across the biofilter were measured when the biofilm shearing method was used to manage bed growth compared to siphoning. The biofilm shearing method was also more effective in controlling bed growth, resulted in less sand loss, and required substantially less labor than siphoning which was a large contrast from the labor required using the bed siphoning and sand replacement technique. The fluidized-sand biofilters removed 66–82% of the cBOD5 each pass and 86–88% of the TAN when bed growth was controlled using biofilm shearing. Outlet cBOD5 and TAN concentrations were reduced to 1.7±0.4mg/L and 0.11±0.04mg/L, respectively and outlet nitrite was 0.10±0.02mg/L when using biofilm shearing. Total phosphorous removal efficiency was 15–41% across the biofilters, and TSS removal was inconsistent but was achieved at inlet concentrations above 10mg/L for both bed management techniques. Results indicate that full-scale fluidized sand biofilters can effectively treat high volume, dilute aquaculture effluents.
Graphitic carbon nitrides (g-C3N4), which possess distinctive graphite-like structure, and their composites have found relevance in several applications. This is attributed to their favorable band ...gap, metal-free nature, high thermal and photo-stability. Other properties including good mechanical properties, chemical inertness, non-toxicity, good biocompatibility and excellent electroluminescent properties have also accentuated their increased applications in different areas. Entirely new properties are obtained when they combine with other nanomaterials to form nanocomposites, and all these properties are now being explored for various benefits. This review highlights the historical background of g-C3N4, the recent progress in the application of the materials in its pristine form, the composite with different inorganic compounds and nanomaterials. Particular attention is given to their applications in nitrogen fixation, as reference material for differentiating oxygen site, in energy storage device, sensing, chemical synthesis, water splitting, photocatalytic heavy metal ions reduction, environmental remediation from pollutants and medicine. The properties were highlighted and different applications were discussed, with the aim of exploring other new areas of applications of g-C3N4. The different routes that have been utilized for the synthesis of g-C3N4, the various nanostructures obtained and the analytical techniques that are required for their characterization were discussed. Finally, in the interest of the recent development and focus on photo enhanced process, diverse ways of enhancing the photocatalytic activities of g-C3N4 and its composites were investigated.
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A waste stabilisation pond (WSP) system formed by two anaerobic ponds, a facultative pond and a maturation pond was studied from December 2003 to September 2004 in north-western Spain in order to ...evaluate its efficiency in the removal of faecal indicator bacteria (total coliforms, Escherichia coli, faecal streptococci), coliphages, helminth eggs and protozoan (oo) cysts (Cryptosporidium and Giardid). Furthermore, sediment samples were collected from the bottom of the ponds to assess the settling rates and thus determine the main pathogen removal mechanisms in the WSPs system. The overall removal ranged from 1.4 log units for coliphages in the cold period to 5.0 log units for E. coli in the hot period. Cryptosporidium oocysts were reduced by an average of 96%, Giardia cysts by 98% and helminth eggs by 100%. The anaerobic ponds showed significantly higher surface removal rates (4.6, 5.2 and 3.7 log (oo) cysts/eggs removed m⁻² day⁻¹, respectively) than facultative and maturation ponds. Sunlight and water physicochemical conditions were the main factors influencing C. parvum oocysts removal both in the anaerobic and maturation ponds, whereas other factors like prédation or natural mortality were more important in the facultative pond. Sedimentation, the most commonly proposed mechanism for cyst removal had, therefore, a negligible influence in the studied ponds.
The solid waste collected from a local silica gel factory was utilized as an adsorbing media for the removal of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) after its surface modification ...with cationic surfactant. Characterization was carried out using thermogravimetric analysis of raw and modified waste. The experiments on the sorption process were conducted for kinetic analysis, effect of initial 2,4-D concentration, adsorbent dose, dissolved salts, pH, surfactant surface coverage, temperature, and shaking speed to understand sorption behavior in batch mode. Presence of electrolyte, solution pH, and temperature were found to affect the performance of the adsorbent. The sorption was found to best follow the pseudo-second order reaction kinetics model and the Redlich-Peterson isotherm model. The studies revealed surfactant-modified silica gel waste (SMSGW) to be an efficient adsorbing media for removal of 2,4-D.
'Sustainable Food Waste-to-Energy Systems' assesses the utilisation of food waste in sustainable energy conversion systems. It explores all sources of waste generated in the food supply chain ...(downstream from agriculture), with coverage of industrial, commercial, institutional and residential sources. It provides a detailed analysis of the conventional pathways for food waste disposal and utilisation, including composting, incineration, landfilling and wastewater treatment.
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