Decolourisation of Sewage using Commercial Tannin-Based Coagulant

In this work, the effectiveness of removing colour and total suspended solid (TSS) from complex organic particulate artificial sewage (COPAS) via the coagulation process was studied. Organo-floc (OF), a tannin-based coagulant derived from the plant was used as a coagulant. OF was applied in a jar test experiment at the various dosages at 57 rpm for 5 min, and 30 min sedimentation time to find out the optimum dosage for colour and TSS removal. Zeta potential, pH and conductivity were also analysed. Experiment with tannin dosage of 125 ppm resulted in the highest colour and TSS removal of 94% and 79%, respectively. Organo-floc showed promising results in decolourisation and TSS removal from artificial sewage.

An LBM Study of the Sedimentation Behaviors of Double Particles With Non-Identical Sizes

In this work, the size effects on the sedimentation behaviors of two non-identical particles are investigated through the lattice Boltzmann method (LBM). The method is first validated by simulating the settling process of single and double particles, which agrees well with analytical and previous results. Then the hydrodynamic behaviors of double non-identical-size particles settling in an infinite-long narrow channel are investigated, in which the larger particle is initially placed above the smaller one. Different sedimentation behaviors are observed with different diameter ratios in the present work. In the first Draft-Kiss-Tumble (DKT) cycle, it is observed that the time durations of both drafting state and kissing state are shortened by the increase of the diameter ratio γ . Considering a longer sedimentation time, three different settling modes are observed with different diameter ratios, which can be summarized as: (1). Repeated DKT cycle (1.0 ≤ γ ≤ 1.13); (2). Repeated DT-DKT after the first DKT cycle (1.14 ≤ γ ≤ 1.22); (3). Separation after the first DKT cycle (1.23 ≤ γ). It should be noted that Mode 2 is first defined in this work, which helps explain the divergence in the threshold diameter ratios of the recurrence of DKT cycles proposed in the previous literatures. In addition, the periodical length of the repeated cycles experiences instant increase and decrease against the diameter ratio near the transition from Mode 1 to Mode 2, while an instant increase is also observed near the threshold diameter ratio between Mode 2 and Mode 3.

Treatment of highly turbid water in disaster conditions using coagulation-flocculation process: modeling and optimization

In the present research, the coagulation-flocculation (CF) process was used to eliminate highly turbid water in disaster conditions. To better understand the efficiency of the system, the impact of various numerical factors namely; initial turbidity (10–350 NTU), pH (5–9), coagulant dosage (50–250 mg/L), rapid mixing (120–280 rpm), slow mixing (30–50 rpm), and sedimentation time (10–50 min) were optimized through the central composite design (CCD) under response surface methodology (RSM). Based on analysis of variance (ANOVA), the quadratic model was more suitable for the dataset with R2 = 0.85 for removing turbidity. Moreover, the results of the present study revealed that the highest turbidity removal (99.14%) was observed at pH (9), alum dosage (50 mg/L), initial turbidity (350 NTU), rapid mixing (280 rpm), slow mixing (50 rpm), and sedimentation time (50 min). Furthermore, the residual turbidity at the maximum efficiency of the system was 3 NTU.

Treatment of Palm Oil Refinery Effluent Using Tannin as a Polymeric Coagulant: Isotherm, Kinetics, and Thermodynamics Analyses

The refining of the crude palm oil (CPO) generates the palm oil refinery effluent (PORE). The presence of high contents of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity, and suspended solids (SS) in PORE encourages the determination of an effective treatment process to minimize the environmental pollution and preserve aquatic life. In the present study, a biodegradable natural polymer, namely tannin, was utilized as a coagulant to treat PORE. The coagulation experiment was conducted using a jar test apparatus. The tannin coagulation efficiency was evaluated based on the BOD, COD, turbidity, and SS removal from PORE by varying the tannin dose (50–300 mg/L), pH (pH 4–10), treatment time (15–90 min), and sedimentation time (15–90 min). It was found that the maximum removal of BOD, COD, turbidity, and SS was 97.62%, 88.89%, 93.01%, and 90.21%, respectively, at pH 6, a tannin dose of 200 mg/L, 60 min of coagulation time, and 60 min of sedimentation time. Analyses of isotherm models revealed that the Freundlich isotherm model was well fitted with the coagulation study. Kinetics studies show that the pseudo-second-order kinetics model was the well-fitted kinetics model for the BOD, COD, turbidity, and SS removal from PORE using tannin as a polymeric coagulant. The determination of thermodynamics parameters analyses revealed that BOD, COD, turbidity, and SS removal from PORE was spontaneous, exothermic, and chemical in nature. The finding of the present study shows that tannin as a natural polymeric coagulant would be utilized in PORE treatment to avoid toxic sludge generation.

A novel passive filtration system for splash-lubricated gearboxes: Part 1

Splash-lubricated gearboxes are widely used in many industries. Contaminant removal systems are rarely employed in splash-lubricated gearboxes, such as some gearboxes are used in helicopters and mining machines. The maintenance of lubrication systems in those machines relies on periodic onsite inspection and lubricant change. However, wear debris generated during operation will suspend in lubricant and cause damage to contacting surfaces of gearbox’s components. In this first part of a two-part paper, a novel light-weight passive filtration system that utilises gravitational sedimentation and shape memory alloys is presented for unfiltered splash-lubricated gearboxes. A predictive model is developed for the estimation of flake-like wear particles’ settling behavior in the lubricant. Experiments based on a simplified test rig are also conducted to validate the theoretical results. This mathematical model can also be used to elucidate the impact of sedimentation time of wear particles on the cleanliness of the lubricant after the installation of passive filtration system.

Settling process of cassava starch using natural coagulant from Moringa oleifera Lam seed extract

Cassava starch has many known applications in food, paper, glue and textile industries, including even biodegradable packaging. In small and medium industries, the starch is obtained by washing the peeled and grinded manioc roots, followed by leaving the washwater for settling before drying the concentrated slurry. Since starch particles are very fine and have a low density, their settling time is high, resulting in a batch operation that lasts for 18 to 24 h. Therefore, it becomes suitable to form larger and heavier starch sets by means of applying coagulants, allowing the particles to settle faster. In the work reported here, the natural coagulant M. oleifera seed extract was used to decrease the settling time of the cassava starch. The effect of the initial concentration of the particles and the coagulant content on the final sedimentation time was evaluated on the batch settling tests. The results showed that the use of the coagulant reduced the sedimentation time in a beaker from 14h to 2h, allowing a quick batch operation.

14C Dated Chronology of the Thickest and Best Resolved Loess/Paleosol Record of the LGM from SE Hungary Based on Comparing Precision and Accuracy of Age-Depth Models

ABSTRACTThe Madaras profile found at the northernmost fringe of Bácska loess plateau is one of the thickest and best-developed last glacial loess sequences of Central Europe. The 10-m profile corresponds to a period between 29 and 12 b2k. To unravel feedback to small-scale centennial climatic fluctuations at our site, recorded in the Greenland ice and North Atlantic marine cores, construction of a reliable chronology is needed. Reliability is expressed in terms of best achievable chronological precision. Accuracy however is based on choosing the model best describing the sedimentological features of our profile. Five different age-depth models had constructed and compared relying on 15 14C dates using various statistical, probabilistic approaches to choose the model with the highest achievable precision. Accuracy was also evaluated using accumulation rates against stratigraphy. Models constructed using the computer program Bacon performed best in terms of achieving the best possible stratigraphic accuracy. Seven meters of the profile represents the period of the LGM. The average sedimentation time was 16.8 yr/cm with the highest confined to the period of the LGM. Calculated average sedimentation rates were 4 times higher than previously reported. The peak accumulation periods are dated to the nadir of the LGM.

Chemical affinity and dispersibility of boron nitride nanotubes

The chemical affinity of purified boron nitride nanotubes (BNNTs) is measured in terms of Hansen solubility parameters, taking into account relative sedimentation time in various solvents. This improves predictions for the dispersion of BNNTs.