Empty Time Research Articles

Study on the Arsenate Removal from Raw As(V)-Rich Wastewater Using Zero-Valent Iron

Due to the large volumes of solid waste produced by the traditional arsenic-rich lime iron salt precipitation method treatment produced during wet-smelting by precious metal workshops, raw As(V)-rich wastewater from a domestic metallurgical enterprise was chosen as the research object. Zero-valent iron (ZVI) was used to remove arsenate (As(V)) from raw wastewater. Factors affecting the adsorption of As(V), such as the ZVI size and adsorption time, were investigated. The As(V) removal percentage was >98.2% when using 40, 100, 250, or 300 mesh ZVI in a 2.8 mg·L−1 As(V) solution at pH 7, with an iron mass–wastewater ratio of 5 g/100 mL, and 12 h reaction time. The As(V) removal percentage was >86.5% when using 40 mesh ZVI after 50 min of reaction. A comprehensive evaluation was performed on the effects of factors such as cost and water head loss. Here, 40 mesh ZVI was used for column-based separation, in which the mass of solid waste was very small. Column experiments indicated that the adsorbent more efficiently eliminated arsenate in comparison to the earlier reported adsorbents. High bed volumes (BV) of 3200 BV, 6300 BV, and 8400 BV up to a breakthrough concentration of 100 μg·L−1 were achieved for arsenate removal in the presence of 2.8 mg·L−1 of arsenic. The empty bed contact times (EBCTs) were 2.6 min, 5.1 min, and 9.8 min, respectively. Furthermore, the concentrations of other pollutants such as Cu2+, Zn2+, F−, Cd2+, Cr6+, Pb2+, and F- met the national discharge standard. The elimination of As(V) and other heavy metals from solutions employing ZVI is efficient, cheap, and produces no secondary environmental pollution, making it an ideal candidate for heavy metal removal from wastewater.

Laboratory and pilot-scale UV, UV/H2O2, and granular activated carbon (GAC) treatments for simultaneous removal of five chemicals of emerging concerns (CECs) in water

This study assessed the efficacy of laboratory and pilot-scale (1) UV photolysis, (2) combined UV and hydrogen peroxide oxidation (UV/H2O2), (3) granular activated carbon (GAC) adsorption, and (4) UV/H2O2 followed by GAC, for simultaneous removal of contaminants of emerging concerns (CECs) in water. Five globally relevant CECs from five different contaminant classes were selected as target CECs to represent the wide range, i.e., N-nitrosodimethylamine (NDMA) as a disinfection by-product, trimethoprim (TMP) as a pharmaceutical, triclosan (TCS) as a personal care product, atrazine (ATZ) as a herbicide, and estrone (E1) as a steroid hormone. Highly photosensitive compounds like NDMA and TCS were easily degraded by UV (>75%) and UV/H2O2 (>80%) with direct photolysis as the main removal mechanism. Their removal efficiencies were less affected by the presence of other CECs and the water matrix than the other CECs. The effects of competitive adsorption among CECs and the water matrix was more profound for moderately hydrophobic or less hydrophilic compounds, e.g., TMP, ATZ, and E1. The laboratory-scale results showed the application of a single treatment could not efficiently remove the target CECs. Hence the combination of treatments was employed in the pilot-scale experiments, which assessed the effectiveness of UV/H2O2 (1000 mJ/cm2 and 4 mg/L H2O2) followed by GAC (empty bed contact time 3.5–28 min) in removing target CECs at their environmentally relevant concentrations. Our findings suggest that UV/H2O2 followed by GAC would serve as an excellent multi-barrier for efficiently removing a wide range of CECs in water.

Removal of ammonium from wastewater by zeolite synthetized from volcanic ash: Batch and column tests

Volcanic ash (VA) fallout during explosive activity of Mt. Etna (Sicily, Italy) negatively impacts the economy of local municipalities due to the management and disposal costs. In order to investigate an alternative use of VA in the civil and environmental engineering field, zeolites synthetized from VA were employed to remove ammonium from various aqueous solutions. Specifically, batch adsorption experiments were conducted to assess the effect of different synthesis conditions (e.g., incubation temperature, use of seawater or distilled water, VA particle size) on the adsorption capacity of ammonium on the produced zeolites. Adsorption isotherms were well fitted by Freundlich model and showed that zeolite synthetized at 70 °C using distilled water (C1H70) exhibited the highest adsorption capacity (~18.4 mg g−1). The observed ammonium adsorption capacity is higher or comparable to other natural or synthetized zeolites reported in literature. C1H70 was used in column experiments under different operational conditions, including initial ammonium concentration (10 and 40 mg L−1), empty bed contact time (EBCT, 4 and 8 min) and water quality (deionized water vs. secondary effluent wastewater). The Dose-Response model showed the best fitting in describing the breakthrough curves. Obtained results showed a good removal of ammonium even though the adsorption capacity decreased in presence of competing ions (e.g., calcium) and when tap water or wastewater was used. Moreover, the adsorption capacity of C1H70 regenerated through NaCl solution was found similar to the fresh C1H70. However, the regenerated zeolite was characterized by a slower mass transfer process. Overall, synthetized zeolites from VA can be used to remove ammonium from wastewater, reducing both the landfilling of VA and the extraction of natural zeolite under the circular economy perspective.

Arsenite removal from drinking water by bark-based magnetic iron oxide particle (BMIOP): a column study.

The removal of arsenite [As(III)] from drinking water was investigated in a column at flow rates of 2.0 and 5.0mL/min (up-flow direction) using bark-based magnetic iron oxide particles (BMIOP) prepared by coating (Fe(NO3)3.9H2O) over Tamarindus Indica bark. The BMIOP was compared with regenerated BMIOP, commercial activated carbon, commercial activated alumina (Al2O3). At 2.0mL/min, empty bed contact time (EBCT), breakthrough time (BT), the volume of treated water and breakthrough capacity (BC) on fresh BMIOP were found to be 6.8min, 33.15h, 4.380 L and 0.742mg/g, respectively, and at 5.0mL/min, were found to be 4.1min, 13h, 3.675 L and 0.453mg/g respectively. EBCT, BT and BC were increased by 65.85%, 155% and 63.79%, respectively, as the flow rate was reduced from 5.0 to 2.0mL/min. After regeneration of BMIOP, EBCT, BT, saturated time, BC and saturation capacity (SC) were reduced by 21.95%, 15.38%, 55.15%, 16.78% and 29.71%, respectively. The BC of fresh BMIOP was increased by factors 4.15, 3.60 and 1.20 and SC by factors 9.51, 7.88 and 1.42 compared to commercial activated carbon, commercial activated Al2O3 and regenerated BMIOP, respectively. Logit model could be used for the design of the adsorption column. Thomas model and artificial neural network (ANN) were applied to predict the characteristic column parameters useful for process design. Quality of treated water meets BIS requirements. Toxicity Characteristic Leaching Procedure (TCLP) and semi-dynamic tests show that the exhausted BMIOP is safe for disposal in a secure landfill; hence, BMIOP has been proved to separate As(III) from water.

Evaluating the relative adsorption and biodegradation of 2-methylisoborneol and geosmin across granular activated carbon filter-adsorbers

This study investigated the relative contributions of adsorption vs. biodegradation towards 2-methylisoborneol (MIB) and geosmin removal in the granular activated carbon (GAC) harvested from six filter-adsorbers in three drinking water treatment plants in the Great Lakes region. Column tests using azide-treated (sterilized) and untreated GAC in parallel were used to isolate the two effects. It was identified that substantial MIB and geosmin biodegradation in the GAC was occurring in one location, and that GAC in some cases had significant adsorption capacity after as much as 9 years of operation. Four alternative biological parameters (adenosine triphosphate, esterase activity, phosphatase activity, and 14C-glucose respiration rate) were measured to quantify the biological activity of the GAC, and 14C-glucose respiration rate was identified to be a potential indicator for GAC biodegradative capacity in terms of MIB, geosmin, and dissolved organic carbon. Several potential MIB and geosmin biodegradation products were also identified using non-targeted screening analysis. By using the new tools identified in this study, we can begin to better understand where adsorption vs. biodegradation may predominate under real-world conditions (e.g., different temperatures, influent concentrations, and empty bed contact time), leading ultimately to more cost-effective use of GAC.

Thiosulfate as external electron donor accelerating denitrification at low temperature condition in S0–based autotrophic denitrification biofilter

This study was carried out to determine the inhibition of low temperature on the performance of S0–based autotrophic denitrification (S0–SAD) biofilter, and proposed to enhance the nitrate removal efficiency with thiosulfate as external electron donor. With the decline of temperature from 30 °C to 10 °C at 0.25 h of empty bed contact time (EBCT), the nitrate removal rate presented a logarithmical drop, and the effluent nitrate dramatically increased from 9.19 mg L−1 to 15.13 mg L−1. EBCT was prolonged until 0.33 h for 20 °C, 0.66 h for 15 °C and 1.5 h for 10 °C, respectively, to maintain the effluent nitrate below 10 mg L−1. Such excessive variation of EBCT for different temperature is undoubtedly incredible for practical engineering. Thiosulfate, as the external electron donor, was adopted to compensate the efficiency loss during temperature decrease, which significantly prompted nitrate removal rate to 0.59, 0.53 and 0.31 kg N m−3 d−1 at 20 °C, 15 °C and 10 °C conditions, respectively, even at a short EBCT of 0.25 h. It not only acted as compensatory electron donor for nitrate removal, but also promoted the contribution of elemental sulfur via accelerating the DO consumption and extended larger effective volume of S0–layer for denitrification. Meanwhile, the significant enrichment of Sulfurimonas and Ferritrophicum provided biological evidences to the enhancement process. However, the incomplete consumption of thiosulfate was observed especially at EBCT of 0.25 h and 10 °C, and the thiosulfate runoff needs to be concerned in case of contaminating the effluent. Herein, approximately extending EBCT to 0.66 h and decreasing thiosulfate dosage were conducted simultaneously, thereby achieving 100% thiosulfate utilization efficiency and expected nitrate removal. This study provided a fundamental guidance to design and operate S0–SAD biofilter in response to seasonal temperature variation for practical engineering.

Optical Feedback Linear Cavity Ringdown Spectroscopy

Optical feedback cavity ringdown spectroscopy is presented with a linear Fabry–Pérot cavity and a cost-effective DFB laser. To circumvent the low coupling efficiency caused by the broad laser linewidth, an optical feedback technique is used, and an enhanced coupling efficiency of 31%, mainly limited by impedance mismatch and mode mismatch, is obtained. The trigger of the ringdown event is realized by the shutoff of the laser driving current, and a novel method with the aid of one electronic switch is applied to avoid the ringdown events excited by the unexpected cavity modes during the process of laser current recovery. As a result, the ringdown signal with a signal-to-noise ratio of 2500 is achieved. Through continuous monitoring, the fractional uncertainty of the empty cavity ringdown times is assessed to be 0.04%. An Allan variance analysis indicates a detection sensitivity of 4.3 × 10−10 cm−1 is resulted at an integration time of 120 s, even with a moderate finesse cavity. To further improve the long-term stability, we regularly rectify the empty cavity ringdown time, and an improvement factor of 2.5 is demonstrated.

Obstinate memory: Working-class politics and neoliberal forgetting in the United Kingdom and Chile

In the 40 years since Chile and the United Kingdom became the crucibles of neoliberalization, working-class agency has been transformed, its institutions systematically dismantled and its politics, after the continuity neoliberalism of both the UK Blair government and the Chilean Concertación, in a crisis of legitimacy. In the process, memories of struggle have been captured within narratives of ‘capitalist realism’ (Fisher) – the present, past and future collapsed into Walter Benjamin’s ‘empty homogeneous time’. This article explores ways in which two traumatic moments of working-class struggle have been narrativized by the media in the service of this ‘presentism’: the 1973 coup in Chile and the 1984–1985 Miners’ Strike in the United Kingdom. We argue that the use of ‘living history’ or bottom-up approaches to memory provides an urgently needed recovery of disruptive narratives of class identity and offers a way of reclaiming alternative futures from the grip of reductive economic nationalism.

Relationships among the Word-Finding Behaviors Ratio, Subjective Memory, and Objective Memory in Healthy Elderly Adults

Purpose: The purpose of this study is to identify relationships among the word-finding behaviors ratio using discourse production task, subjective memory, and objective memory in healthy elderly adults.Methods: Ninety-five healthy elderly adults participated in this study. Participants were used to picture description tasks. To evaluate the subjective memory deficit of the elderly, Subjective Memory Complaints Questionnaire (SMCQ) was used, and to evaluate the objective memory deficit, the Seoul Verbal Learning Test (SVLT) was used.Results: First, the ratio of word-finding behaviors in the elderly appeared in the order of empty words, repetitions, insertions, time fillers, delays, word reformulations, and substitutions. Second, the SMCQ score, which evaluates subjective memory, showed a significant positive correlation with the ratio of global index, repetitions, and insertions. Third, the ratio of global index, repetitions, insertions, delays, and substitutions of word-finding behaviors were significantly correlated with the objective memory of the elderly. Finally, the most significant predictor variable in the global index ratio of word-finding behaviors of the elderly was the delayed recall score of SVLT.Conclusion: The results of this study suggested that the ratio of wordfinding behaviors by the spontaneous speech-based naming test is closely related to the subjective and objective memory in healthy elderly adults.

Microbial Degradation Pathways of Acrylic Paint Thinner Gas in Biotrickling Filter and Comparison of Kinetic Models Under Different Gas Concentrations

In this study, the effect of inlet concentration of pollutants, empty bed residence time (EBRT) and liquid recycling velocity on the performance of the BTF was explored. The results showed the best operating characteristics of the biotrickling filter for this study were at an inlet concentration of 500 mg/m3�Cthe EBRT of 300s and liquid recycling velocity of 25.46 m h-1. At this condition, the total removal efficiency of pollutants can reach more than 90%. Among them, the removal efficiency of toluene and ethylbenzene was above 95%, and the xylene (m-xylene, o-xylene) could reach more than 70%, corresponding to elimination capacities (ECs) of 3.02 �} 0.33 g m-3 h-1, 1.81 �} 0.2 g m-3 h-1, 0.60 �} 0.07 g m-3 h-1. Through the fatty acid identification system and 16S rDNA identification, it could be found that the four dominant bacteria (Bacillus cereus, Bacillus subtilis, Acinetobacter calcoaceticus, Belem Bacillus) had a significant effect on the removal of acrylic paint thinner. According to the detection of organic compounds by gas chromatography and the corresponding enzymes produced by four dominant bacteria, the pathways for microorganisms to degrade pollutants could be inferred. The absorption-biofilm theory and the adsorption-biofilm theory were used to simulate and verify the degradation process of exhaust gas at different concentrations respectively.

Extremely acidic condition (pH

Extremely acidic conditions (pH < 1.0) during hydrogen sulfide (H2S) biotreatment significantly reduce the cost of pH regulation; however, there remain challenges to its applications. The present study investigated the H2S removal and biomass variations in biotrickling filter (BTF) under long-term highly acidic conditions. A BTF operated for 144 days at pH 0.5–1.0 achieved an H2S elimination capacity (EC) of 109.9 g/(m3·h) (removal efficiency = 97.0%) at an empty bed retention time of 20 s, with an average biomass concentration at 20.6 g/L-BTF. The biomass concentration at neutral pH increased from 22.3 to 49.5 g/L-BTF within 28 days. In this case, elemental sulfur (S0) accumulated due to insufficient oxygen transfer in biofilm, which aggravated the BTF blockage problem. After long-term domestication under extremely acidic conditions, a mixotrophic acidophilic sulfur-oxidizing bacteria (SOB) Alicyclobacillus (abundance 55.4%) were enriched in the extremely acidic biofilm, while non-aciduric bacteria were eliminated, which maintained the balance of biofilm thickness. Biofilm with optimum thickness ensured oxygen transfer and H2S oxidation, avoiding the accumulation of S0. The BTF performance improved due to the enrichment of active mixotrophic SOB with high abundance under extremely acidic conditions. The mixotrophic SOB is expected to be further enriched under extremely acidic conditions by adding carbohydrates to enhance H2S removal.

Surrogate-based follow-up of activated carbon adsorption preceded by ozonation for removal of bulk organics and micropollutants from landfill leachate

Although combined ozonation with activated carbon (AC) adsorption is a promising technique for leachate treatment, little is known about how ozone-induced changes in leachate characteristics affect the organics adsorption, especially in view of emerging micropollutants (MPs) removal. Furthermore, the online monitoring of MPs is challenging but desirable for efficient treatment operation. This study investigates how preceding ozonation impacts the adsorption of bulk organics (expressed as chemical oxygen demand (COD)) and ozone-recalcitrant MPs, i.e., primidone, atrazine and alachlor, in leachate using batch and column adsorption tests. Additionally, a new surrogate-based model was evaluated for predicting MPs breakthrough. Batch tests revealed that ozonation results in a decreasing apparent affinity of COD towards AC, but the non-adsorbable part did not obviously change. The adsorption of MPs in ozonated leachate was (1–41%) higher than that in non-ozonated leachate, especially for the more hydrophobic alachlor and atrazine, due to a reduced sites competition from bulk organics. Column adsorption showed that ozonation delayed COD and MPs breakthrough due to the reduced COD loading and sites competition, respectively. An increased empty bed contact time (EBCT, 10–40 min) led to an increased COD uptake by a factor of 3.0–3.2 for ozonated and non-ozonated leachates, while MPs adsorption also increased, suggesting that pore blockage rather than site competition could be the dominant inhibitory effect. The data from column adsorption demonstrate the applicability of developed surrogate-based model for predicting MPs breakthrough. Particularly, the fitting parameters were not affected by change of leachate characteristics, while they were impacted by change of EBCT.

Simultaneous biodegradation of BTX by isolated degrading bacterial strains in a newly designed modulated bio-scrubber assisted to airlift parallel bioreactors.

A new approach in this present study, isolated bacteria from refinery sludge were used in a laboratory-scale bio-scrubber, connecting with two parallel airlift bioreactors to eliminate harmful and toxic fumes of BTX. One of the main features of this bio-scrubber is using porous mineral pumice fillers (Lava Rock) inside poly-urethane foam (PUF)module tower, connecting with agitator bio-phasic continuously stirred tank bio-reactor (CSTbR) to increase retention time and contact surface. The bio-scrubber and airlift plug flow bio-reactor(PFbR) were used in parallel with cooling flow to be more efficient in preservation of the corresponding heater and endothermic from removal reactions. Performance of bio-scrubber in removing BTX vapors with 10 % silicone oil and grade 350 poise as organic phase in the inlet concentration range of 180 ± 0.3 to 1950.5 ± 0.1mg /m3 (ppmv) for up to 6 months in two air flow rate's 2.5 and 3.5 (lit/min) that each treatment lasted about 2 months. The rate of biodegradation in this study was carried out by mixing 3 isolated bacteria, obtaining from refinery sludge, named DBIS-03, DTIS-12, and DXIS-09, which they had highest biodegradability than all the isolated strains. The results of BTX biodegradation at each EBRT (Empty Bed Retention Time) showed that the removal efficiency of BTX with isolated bacterial samples was able to grow and multiply on porous fillers and regenerate the growth medium of autotrophic bacterial strain with O2 gas and micronutrients from contaminated air flow with minimum concentration. Benzene, toluene and xylene inputs maximum concentration over a period of 20 days loading, respectively: B :99.2 % (at 2.5 lit/min and 183.2 ± 0.2mg /m3 (ppmv)), T: 98 % (at 2.5 lit/min and 327.1 ± 0.1mg /m3 ( ppmv)) and X: 85.9 % (at 2.5 lit/min and 296.8 ± 0.8mg /m3 (ppmv)) compared to 3.5 lit/min and so show the best performance in removing BTX from polluted air in period of 30 days.

Research on uncertainty of optical feedback linear cavity ringdown spectroscopy

Cavity ring-down spectroscopy (CRDS) is a highly sensitive molecular absorption spectroscopic technology, which has been widely used in mirror reflectance measurement, atmospheric trace gas detection, molecular precision spectroscopy and other fields. It deduces the intracavity absorption by measuring the rapid variation of the ringdown signal. As a result, detector with high linearity, broad bandwidth and low electrical noise is indispensable. Additionally, due to the large noise in laser frequency, low laser to cavity coupling efficiency is resulted. Consequently, the cavity transmission is faint, which deteriorates the detection sensitivity. Optical feedback could address this problem by locking the laser to the cavity longitudinal mode. Then, the laser frequency noise is suppressed and hence better detection sensitivity is expected. Optical feedback CRDS has been widely studied with V-shape cavity. Compared to Fabry-Perot cavity, this cavity geometry is more sensitive to mechanical vibration and possesses lower finesse with an additional mirror. In this paper, optical feedback linear cavity ring-down spectroscopy based on a Fabry-Perot cavity with a finesse of 7800 is presented. The principle of the combination of optical feedback and linear cavity is explained from the perspective of the light phase, which shows the reflection would not generate efficient optical feedback if the feedback phase is properly controlled and laser to cavity locking could be therefore realized. And then, the factors influencing the stability of ring-down signal is analyzed, including the feedback ratio, the trigger voltage for the ringdown event and the distance between the light spot and the detector center. The experimental results show a superior fractional uncertainty of the empty ringdown time of 0.026% could be attained with a low feedback rate (3% FSR), a high ringdown signal trigger threshold (90% cavity mode amplitude) and superposition of the light spot with the detector center. With Allan variance analysis, the white noise response of 1.56×10&lt;sup&gt;-9&lt;/sup&gt; cm&lt;sup&gt;-1&lt;/sup&gt;/ HZ&lt;sup&gt;-1/2&lt;/sup&gt; and the detection sensitivity of .29×10&lt;sup&gt;-10&lt;/sup&gt; cm&lt;sup&gt;-1&lt;/sup&gt; for trace gas detection could be achieved at the integration time of 180 s, corresponding to the lowest CH&lt;sub&gt;4&lt;/sub&gt;concentration detection of 0.35 ppb at 6046.9cm&lt;sup&gt;-1&lt;/sup&gt;. This robust spectroscopic technique paves the way for the construction of high sensitive and stable cavity based instrument for trace gas detection.

Granular activated carbon adsorption of perfluoroalkyl acids from ground and surface water

AbstractAdsorption of perfluoroalkyl acids (PFAAs) by granular activated carbon (GAC) was evaluated in bench‐, pilot‐, and full‐scale studies to determine effects of PFAA characteristics and background organic matter on carbon use rates. Rapid small‐scale column tests (RSSCTs) were conducted according to the proportional diffusivity (PD) design to assess their suitability to predict full‐ or pilot‐scale GAC performance. PFAA removal from groundwater (GW) and coagulated surface water (SW) was studied with two sub‐bituminous coal‐based GACs. In batch tests conducted with pulverized GAC, the GACs performed similarly in GW, but the GAC with the larger mesopore volume was more effective for PFAA removal from SW. In column tests, carbon use rates decreased with increasing PFAA chain length and were lower for GW (total organic carbon [TOC] = 0.7 mg/L) than for SW (TOC = 2.0–2.7 mg/L). The volume of SW that could be treated to 10% or 50% PFAA breakthrough was about 50–60% of the volume of GW that could be treated when comparing pilot‐scale data for SW with full‐scale data for GW. Consistent differences in PFAA adsorption capacity were not observed for empty bed contact times of 13 and 26 min in full‐scale adsorbers treating GW. The PD‐RSSCT simulating PFAA removal from GW consistently overpredicted full‐scale adsorption capacity, on average by ~70%. Using a carbon use rate of &lt;25 mgGAC/Lwater treated) as a criterion for the feasibility of GAC treatment, full‐ and pilot‐scale GAC adsorber data suggest that GAC is a viable treatment option (carbon use rate &lt; 25 mgGAC/Lwater treated) for perfluoroalkylcarboxylic acids with six or more carbon atoms in SW and five or more carbon atoms in GW. For perfluoroalkyl sulfonic acids, GAC treatment is viable for compounds containing four or more carbons based on results obtained with both SW and GW.

Multiobjective Scheduling for Cooperative Operation of Multiple Gantry Cranes in Railway Area of Container Terminal

Railway station plays an important role in improving the operation efficiency of rail-sea intermodal container terminal. The cooperative scheduling of multiple gantry cranes (GCs) can reduce the production and operation cost of railway station. Most studies look into discarding the conflict schemes of GCs, which may obtain excellent scheduling results. These existing conflict-free strategies can not contribute to enhancing the cooperative scheduling performance of multiple GCs. This study integrates container trucks into multiple GCs scheduling environment to eliminate those conflicts, and proposes a mixed-integer programming model considering cooperation between multiple GCs and trucks. The model aims to simultaneously minimize the makespan of the container handling system in station, the total empty travel time of GCs and the total energy consumption of both cranes and trucks. To solve the proposed model, a conflict-free operation strategy for multiple GCs based on hybrid indirect loading and unloading (CFHI) is proposed. CFHI strategy is implemented according to the cooperation between GCs and trucks. An effective multi-objective artificial bee colony algorithm (EMOABC) based on CFHI and fuzzy correlation entropy (FCE) is developed. Within the developed algorithm, an encoding/decoding method based on CFHI is designed to represent and decode the population solutions. The FCE is adopted to evaluate and select the better solutions for next iteration evolution. The effectiveness of the proposed CFHI strategy is verified by comparing it with two popular equipment allocation strategies. Extensive experimental results show that proposed EMOABC is effective to the proposed model. Our findings here have significant implications for the cooperative operation of multiple GCs considering energy consumption in container terminal.

Uncertainty of optical feedback linear cavity ringdown spectroscopy

Cavity ring-down spectroscopy (CRDS) is a highly sensitive molecular absorption spectroscopic technology, which has been widely used in mirror reflectance measurement, atmospheric trace gas detection, molecular precision spectroscopy and other fields. It deduces the intracavity absorption by measuring the rapid variation of the ringdown signal. As a result, detector with high linearity, broad bandwidth and low electrical noise is indispensable. Additionally, owing to the large noise in laser frequency, low laser-to-cavity coupling efficiency is obtained. Consequently, the cavity transmission is faint, which deteriorates the detection sensitivity. Optical feedback can address this problem by locking the laser to the cavity longitudinal mode. Then, the laser frequency noise is suppressed and hence better detection sensitivity is expected. Optical feedback CRDS with V-shape cavity has been widely studied. Compared with Fabry-Perot cavity, this cavity geometry is very sensitive to mechanical vibration and possesses low degree of fineness due to an additional mirror. In this paper, optical feedback linear cavity ring-down spectroscopy based on a Fabry-Perot cavity with a degree of fineness of 7800 is presented. The principle of the combination of optical feedback and linear cavity is explained from the perspective of the light phase, which shows that the reflection will not generate efficient optical feedback if the feedback phase is appropriately controlled and laser to cavity locking can be therefore realized. And then, the factors influencing the stability of ring-down signal are analyzed, including the feedback ratio, the trigger voltage for the ringdown event, and the distance between the light spot and the detector center. The experimental results show that a superior fractional uncertainty of the empty ringdown time of 0.026% can be obtained with a low feedback rate (3% FSR), a high ringdown signal trigger threshold (90% cavity mode amplitude) and superposition of the light spot with the detector center. With Allan variance analysis, the white noise response of 1.6 × 10&lt;sup&gt;–9&lt;/sup&gt; cm&lt;sup&gt;–1&lt;/sup&gt;·Hz&lt;sup&gt;–1/2&lt;/sup&gt; and the detection sensitivity of 1.3 × 10&lt;sup&gt;–10&lt;/sup&gt; cm&lt;sup&gt;–1&lt;/sup&gt; for trace gas detection can be achieved in an integration time of 180 s, corresponding to the lowest CH&lt;sub&gt;4&lt;/sub&gt; concentration detection of 0.35 × 10&lt;sup&gt;–9&lt;/sup&gt; at 6046.9 cm&lt;sup&gt;–1&lt;/sup&gt;. This robust spectroscopic technique paves the way for constructing high-sensitive and stable-cavity based instrument for trace gas detection.

Highly Effective Cow Bone Based Biocomposite for the Sequestration of Organic Pollutant Parameter from Palm Oil Mill Effluent in a Fixed Bed Column Adsorption System.

The reduction of chemical oxygen demand (COD) from palm oil mill effluent (POME) is very significant to ensure aquatic protection and the environment. Continuous adsorption of COD in a fixed bed column can be an effective treatment process for its reduction prior to discharge. Adsorption capacity of bone derived biocomposite synthesized from fresh cow bones, zeolite, and coconut shells for the reduction in the organic pollutant parameter was investigated in this study in a fixed bed column. The effect of influent flow rate (1.4, 2.0, and 2.6 mL/min) was determined at an influent pH 7. The optimum bed capacity on the fabricated composite of surface area of 251.9669 m2/g was obtained at 1.4 mL/min at breakthrough time of 5.15 h influent POME concentration. The experimental data were fitted to Thomas, Adams–Bohart, and Yoon–Nelson models fixed bed adsorption models. It was revealed that the results fitted well to the Adams Bohart model with a correlation coefficient of R2 > 0.96 at different influent concentration. Adsorption rate constant was observed to increase at lower flow rate influent concentration, resulting in longer empty bed contact time (EBCT) for the mass transfer zone of the column to reach the outlet of the effluent concentration. In general, the overall kinetics of adsorption indicated that the reduction in COD from POME using a bone-biocomposite was effective at the initial stage of adsorption. The pore diffusion model better described the breakthrough characteristics for COD reduction with high correlation coefficient. Shorter breakthrough time compared to EBCT before regeneration indicated that the bone composite was suitable and effective for the reduction in COD from POME using fixed bed column adsorption.

A review on treatment of disinfection byproduct precursors by biological activated carbon process

Disinfection by-products (DBPs) in water systems have attracted increasing attention due to their toxic effects. Removal of precursors (mainly natural organic matter (NOM)) prior to the disinfection process has been recognized as the ideal strategy to control the DBP levels. Currently, biological activated carbon (BAC) process is a highly recommended and prevalent process for treatment of DBP precursors in advanced water treatment. This paper first introduces the fundamental knowledge of BAC process, including the history, basic principles, typical process flow, and basic operational parameters. Then, the selection of BAC process for treatment of DBP precursors is explained in detail based on the comparative analysis of dominant water treatment technologies from the aspects of mechanisms for NOM removal as well as the treatability of different groups of DBP precursors. Next, a thorough overview is presented to summarize the recent developments and breakthroughs in the removal of DBP precursors using BAC process, and the contents involved include effect of pre-BAC ozonation, removal performance of various DBP precursors, toxicity risk reduction, fractional analysis of NOM, effect of empty bed contact time (EBCT) and engineered biofiltration. Finally, some recommendations are made to strengthen current research and address the knowledge gaps, including the issues of microbial mechanisms, toxicity evaluation, degradation kinetics and microbial products.

Biological removal of gas‐phase H2S in hollow fibre membrane bioreactors

AbstractBACKGROUNDHydrogen sulphide (H2S) must be treated at its emission source to avoid health risks, odour, and corrosion. Conventional physico‐chemical H2S removal technologies (for example, membrane contactors or chemical scrubbers) have several limitations, such as requiring high amounts of absorption chemicals and energy. In contrast, biological H2S removal technologies are environment friendly, easy to operate, and less expensive due to their low energy requirements. In this study, the feasibility of a porous hydrophilic polyethersulfone hollow fibre membrane bioreactor (HFMB) was tested for the biological removal of gas‐phase H2S by employing three lab‐scale reactors (two biotic and one abiotic). The HFMBs were operated at ~20 °C for ~3 months, employing different H2S inlet loading rates (ILR) and an empty bed residence time of 187 s.RESULTSBiotic performance of the HFMBs demonstrated that the removal efficiency (RE) varied between the different inocula and was in the range of 80–100% for the applied H2S ILR of ~5.0–7.5 g m−3 h−1. The RE reached a constant value of ~100% in both biotic reactors at an ILR of ~17.0 g m−3 h−1 when using acclimatized inoculum. The biotic HFMBs demonstrated ~5–9 times higher H2S flux and ~ 20–26 times higher mass transfer compared to the abiotic control. Surface morphology revealed attached microbial growth on the outer surface of the membranes, while the high throughput sequencing confirmed the richness of H2S oxidizing microbial communities on the shell side.CONCLUSIONThe obtained results confirm that the HFMB configuration is suitable for biological treatment of H2S laden waste gas. © 2021 Society of Chemical Industry (SCI).