The impact of biological activated carbon (BAC), sand filtration (SF) and biological aerated filter (BAF) for removal of the selected organic micropollutants and polyfluoroalkyl substances (PFASs) from secondary effluent was studied. BAC led to greater removal of dissolved organic carbon (43%) than BAF (30%) which in turn was greater than SF (24%). All biological filtration systems could effectively remove most of the selected organic micropollutants, and there was a greater removal of these micropollutants by BAC (76-98%) than BAF (70-92%) or SF (68-90%). It was found that all treatment was effective for removal of the hydrophobic (log D > 3.2) and readily biodegradable organic micropollutants. The major mechanism for the removal of these molecules was biodegradation by the micro-organism and sorption by the biofilm. Compared to organic micropollutants removal, there was a lower removal of PFASs by all treatments, and BAF and SF had a considerably lower removal than BAC treatment. The better removal for all molecule types by BAC was due to additional adsorption capacity by the activated carbon. This study demonstrated that the BAC process was most effective in removing organic micropollutants present in the secondary effluent.
Microbiologically influenced corrosion (MIC) is among the common corrosion types for buried and deep-water pipelines that result in costly repair and pipeline failure. Sulfate-reducing bacteria (SRB) are commonly known as the culprit of MIC. The aim of this work is to investigate the performance of combination of ultrasound (US) irradiation and ultraviolet (UV) radiation (known as Hybrid soliwave technique, HyST) at pilot scale to inactivate SRB. The influence of different reaction times with respect to US irradiation and UV radiation and synergistic effect toward SRB consortium was tested and discussed. In this research, the effect of HyST treatment toward SRB extermination and corrosion studies of carbon steel coupon upon SRB activity before and after the treatment were performed using weight loss method. The carbon steel coupons immersed in SRB sample were exposed to HyST treatment at different time of exposure. Additionally, Field Emission Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy were used to investigate the corrosion morphology in verifying the end product of SRB activity and corrosion formation after treatment. Results have shown that the US irradiation treatment gives a synergistic effect when combined with UV radiation in mitigating the SRB consortium.
This work demonstrated the synthesis of carbon nanotubes (CNTs) on powder activated carbon (PAC) impregnated with Ni-catalyst through chemical vapour deposition. The optimized effects of reaction temperature, time and feedstock flow rates on CNT growth were examined. Potassium permanganate (KMnO4) and potassium permanganate in acidic solution (KMnO4/H2SO4) were used to functionalize CNTs samples. A primary screening of methylene blue (MB) adsorption was conducted. The chemical, physical and morphological properties of the adsorbent with the highest removal efficiency were investigated using FESEM, EDX, TEM, BET surface area, RAMAN, TGA, FTIR, and zeta potential. The resulting carbon nanotube-loaded activated carbons possessed abundant pore structure and large surface area. The MB removal by the as-synthesized CNTs was more remarkable than that by the modified samples. Adsorption studies were carried out to evaluate the optimum conditions, kinetics and isotherms for MB adsorption process. The response surface methodology-central composite design (RSM-CCD) was used to optimize the adsorption process parameters, including pH, adsorbent dosage and contact time. The investigation of the adsorption behaviour demonstrated that the adsorption was well fitted with the pseudo-second-order model and Langmuir isotherm with the maximum monolayer adsorption capacity of 174.5 mg/g. Meanwhile, the adsorption of MB onto adsorbent was driven by the electrostatic attraction and π-π interaction. Moreover, the as-obtained CNT-PAC exhibited good reusability after four repeated operations. In view of these empirical findings, the low-cost CNT-PAC has potential for removal of MB from aqueous solution.
The present work reports the extraction of phenolic compounds from Polygonum minus using ionic liquid as extracting solvent. In this work, 1-Butyl-3-methylimidazolium hydrogen sulfate [BMIM][HSO4] was used for the extraction of bioactive compounds. Accordingly, ionic liquids based microwave-assisted extraction treatment for separating of bioactive compounds from polygonum minus was first performed in the present study. The results obtained in this work have high extraction yield in comparison with conventional solvent. UV/Vis results showed that microwave synthesis was fast, well dispersed and nanosized copper nanoparticle (CuNPs) in comparison with conventional synthesis. CuNPs was characterised by X-Rays diffractometer (XRD), Fourier transform infrared (FTIR), dynamic light scattering (DLS), field emission scanning electron microscopy combined with energy dispersive x-rays (FESEM-EDX), and thermogravimetric analysis (TGA). All the instrumental analyses confirmed the particles were nanosized. Furthermore, the antibacterial activity of as-synthesised CuNPs showed effective inhibitory zone against three different bacteria. The photocatalytic degradation of copper nanoparticles was studied using methylene blue (MB) and methyl orange (MO) dyes under UV light and degraded 99.9% within short time 8 and 7 min.
The state of activated sludge wastewater treatment process (AS WWTP) is conventionally identified by physico-chemical measurements which are costly, time-consuming and have associated environmental hazards. Image processing and analysis-based linear regression modeling has been used to monitor the AS WWTP. But it is plant- and state-specific in the sense that it cannot be generalized to multiple plants and states. Generalized classification modeling for state identification is the main objective of this work. By generalized classification, we mean that the identification model does not require any prior information about the state of the plant, and the resultant identification is valid for any plant in any state. In this paper, the generalized classification model for the AS process is proposed based on features extracted using morphological parameters of flocs. The images of the AS samples, collected from aeration tanks of nine plants, are acquired through bright-field microscopy. Feature-selection is performed in context of classification using sequential feature selection and least absolute shrinkage and selection operator. A support vector machine (SVM)-based state identification strategy was proposed with a new agreement solver module for imbalanced data of the states of AS plants. The classification results were compared with state-of-the-art multiclass SVMs (one-vs.-one and one-vs.-all), and ensemble classifiers using the performance metrics: accuracy, recall, specificity, precision, F measure and kappa coefficient (κ). The proposed strategy exhibits better results by identification of different states of different plants with accuracy 0.9423, and κ 0.6681 for the minority class data of bulking.
The immobilisation of Chlorella vulgaris 211/11B entrapped in combinations of natural matrices to simplify the harvesting process was demonstrated in this study. Three combinations of matrices composed of calcium alginate (CA) and sodium alginate (SA), sodium carboxymethyl cellulose (CMC) and SA, and mixed matrices (SA, CA, and CMC) were investigated. The number of cells grown for each immobilised matrix to microalgae volume ratios (0.2:1-1:1) were explored and compared with using SA solely as a control. The optimum volume ratios obtained were 1:1 for SA, 0.3:1 for CA and SA, 1:1 for CMC and SA, and 0.3:1 for mixed matrices. The immobilised microalgae of mixed matrices exhibited the highest number of cells with 1.72 × 109 cells/mL at day 10 and 30.43% of oil extraction yield followed by CA and SA (24.29%), CMC and SA (13.00%), and SA (6.71%). Combining SA, CA, and CMC had formed a suitable structure which improved the growth of C. vulgaris and increased the lipid production compared to the immobilisation using single matrix. Besides, the fatty acids profile of the oil extracted indicates a high potential for biodiesel production.
Magnetic nanocomposites adorned with calixarene were successfully prepared by immobilizing diethanolamine functionalized p-tert-butylcalix[4]arene (DEA-Calix) onto silica-coated magnetic nanoparticles (MNPs). The synthesis, surface morphology, purity, elemental composition and thermal stability of newly prepared nanocomposites were analyzed using FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Magnetic solid-phase adsorption (MSPA) was employed to explore the adsorption behavior of DEA-Calix-MNPs towards Pb(II) from water samples prior to its flame atomic absorption spectrometric analysis. The essential analytical factors governing the adsorption efficiency such as solution pH, mass of adsorbent, concentration and contact time have been investigated and optimized. The results depict that DEA-Calix-MNPs has excellent adsorption efficiency 97% (at pH 5.5) with high adsorption capacity of 51.81 mg g-1 for Pb(II) adsorption. Additionally, kinetic and equilibrium studies suggested that Pb(II) adsorption process follows a pseudo-second-order model and Langmuir isotherms, respectively. Real sample analysis also confirmed field applicability of the new DEA-Calix-MNPs adsorbent.
Membrane fouling during the filtration process is a perennial issue and could lead to reduced separation efficiency. In this work, poly(citric acid)-grafted graphene oxide (PGO) was incorporated into a matrix of single-layer hollow fibre (SLHF) and dual-layer hollow fibrr (DLHF) membranes, respectively, aiming to improve membrane antifouling properties during water treatment. Different loadings of PGO ranging from 0 to 1 wt% were first introduced into the SLHF to identify the best PGO loading for the DLHF preparation with its outer layer modified by nanomaterials. The findings showed that at the optimized PGO loading of 0.7 wt%, the resultant SLHF membrane could achieve higher water permeability and bovine serum albumin rejection compared to the neat SLHF membrane. This is due to the improved surface hydrophilicity and increased structural porosity upon incorporation of optimized PGO loading. When 0.7 wt% PGO was introduced only to the outer layer of DLHF, the cross-sectional matrix of the membrane was altered, forming microvoids and spongy-like structures (more porous). Nevertheless, the BSA rejection of the membrane was improved to 97.7% owing to an inner selectivity layer produced from a different dope solution (without the PGO). The DLHF membrane also demonstrated significantly higher antifouling properties than the neat SLHF membrane. Its flux recovery rate is 85%, i.e. 37% better than that of a neat membrane. By incorporating hydrophilic PGO into the membrane, the interaction of the hydrophobic foulants with the membrane surface is greatly reduced.
As the population increases, energy demands continue to rise rapidly. In order to satisfy this increasing energy demand, biogas offers a potential alternative. Biogas is economically viable to be produced through anaerobic digestion (AD) from various biomass feedstocks that are readily available in Malaysia, such as food waste (FW), palm oil mill effluent (POME), garden waste (GW), landfill, sewage sludge (SS) and animal manure. This paper aims to determine the potential feedstocks for biogas production via AD based on their characteristics, methane yield, kinetic studies and economic analysis. POME and FW show the highest methane yield with biogas yields up to 0.50 L/g VS while the lowest is 0.12 L/g VS by landfill leachate. Kinetic study shows that modified Gompertz model fits most of the feedstock with R 2 up to 1 indicating that this model can be used for estimating treatment efficiencies of full-scale reactors and performing scale-up analysis. The economic analysis shows that POME has the shortest payback period (PBP), highest internal rate of return (IRR) and net present value (NPV). However, it has already been well explored, with 93% of biogas plants in Malaysia using POME as feedstock. The FW generation rate in Malaysia is approximately 15,000 tonnes per day, at the same time FW as the second place shows potential to have a PBP of 5.4 years and 13.3% IRR, which is close to the results achieved with POME. This makes FW suitable to be used as the feedstock for biogas production.
Agro-waste from the bark of Metroxylon sagu (sago) was studied as a low cost and effective oil sorbent in dry and aqueous environments. Sorption study was conducted using untreated sago bark (SB) and esterified sago bark (ESB) in used engine oil. Characterization study showed that esterification has successfully improved the hydrophobicity, buoyancy, surface roughness and oil sorption capacity of ESB. Sorption study revealed that water uptake of SB is higher (30 min static: 2.46 g/g, dynamic: 2.67 g/g) compared with ESB (30 min static: 0.18 g/g, dynamic: 0.14 g/g). ESB, however, showed higher oil sorption capacity in aqueous environment (30 min static: 2.30 g/g, dynamic: 2.14) compared with SB (30 min static: 0 g/g, dynamic: 0 g/g). ESB has shown great poTENTial as effective oil sorbent in aqueous environment due to its high oil sorption capacity, low water uptake and high buoyancy.
The effective removal of o-cresol is currently both an environmental and economic challenge. ZnO is not only an efficient photocatalyst but is also cost effective, as its photoabsorption can extend from the ultraviolet (UV) to the visible range thereby allowing the use of inexpensive visible light sources, such as sunlight. The principal objective of the present work is to investigate the visible light-driven removal of o-cresol from aqueous solution in the presence of 1.0 wt% Mn-doped ZnO. To measure the efficiency ofphotodegradation, the variables studied included the amount ofphotocatalyst, concentration of o-cresol, pH and irradiation time. The concentration ofo-cresol and residual organic carbon was monitored using a UV-visible spectrophotometer, ultra high-pressure liquid chromatography and a total organic carbon analyser. The optimum conditions under which the photodegradation of o-cresol was most favourable corresponded to 1.5 g/l ZnO, 35 ppm o-cresol and pH 9. The ZnO-1 wt% Mn photoprocess has demonstrated reusability for more than three times, which warrants its scale-up from laboratory- to in industrial-scale application.
The capability of the crude extract of Rhodococcus UKMP-5M was enhanced by adopting the technology of immobilization. Among the matrices screened to encapsulate the crude extract, gellan gum emerged as the most suitable immobilization material, exceeding the activity of cyanide-degrading enzyme by 61% and 361% in comparison to alginate carrier and non-immobilized crude extract, respectively. Improved bead mechanical strength which supported higher biocatalyst activity by 63% was observed when concentration of gellan gum, concentration of calcium chloride, number of beads and bead size were optimized. The immobilized crude extract demonstrated higher tolerance towards broad range of pH (5-10) and temperature (30°C-40°C), superior cyanide-degrading activity over time and improved storage stability by maintaining 76% of its initial activity after 30 days at 4°C. Furthermore, repeated use of the gellan gum beads up to 20 batches without substantial loss in the catalytic activity was documented in the present study, indicating that the durability of the beads and the stability of the enzyme are both above adequate. Collectively, the findings reported here revealed that the utilization of the encapsulated crude extract of Rhodococcus UKMP-5M can be considered as a novel attempt to develop an environmentally favourable and financially viable method in cyanide biodegradation.
In this study freely suspended and Ca-alginate immobilized C. vulgaris cells were used for the biosorption of Fe(II), Mn(II), and Zn(II) ions, from the aqueous solution. Experimental data showed that biosorption capacity of algal cells was strongly dependent on the operational condition such as pH, initial metal ions concentration, dosages, contact time and temperature. The maximum biosorption of Fe(II) 43.43, Mn(II) 40.98 and Zn(II) 37.43 mg/g was achieved with Ca-alginate immobilized algal cells at optimum pH of 6.0, algal cells dosage 0.6 g/L, and contact time of 450 min at room temperature. The biosorption efficiency of freely suspended and immobilized C. vulgaris cells for heavy metals removal from the industrial wastewater was validated. Modeling of biosorption kinetics showed good agreements with pseudo-second-order. Langmuir and D-R isotherm models exhibited the best fit of experimental data. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that the biosorption of considered metal ions was feasible, spontaneous and exothermic at 25-45°C. The SEM showed porous morphology which greatly helps in the biosorption of heavy metals. The Fourier transform infrared spectrophotometer (FTIR) and X-rays Photon Spectroscopy (XPS) data spectra indicated that the functional groups predominately involved in the biosorption were C-N, -OH, COO-, -CH, C=C, C=S and -C-. These results shows that immobilized algal cells in alginate beads could potentially enhance the biosorption of considered metal ions than freely suspended cells. Furthermore, the biosorbent has significantly removed heavy metals from industrial wastewater at the optimized condition.
Biological aerated filter (BAF), sand filtration (SF), alum and Moringa oleifera coagulation were investigated as a pre-treatment for reducing the organic and biofouling potential component of an ultrafiltration (UF) membrane in the treatment of lake water. The carbohydrate content was mainly responsible for reversible fouling of the UF membrane compared to protein or dissolved organic carbon (DOC) content. All pre-treatment could effectively reduce these contents and led to improve the UF filterability. Both BAF and SF markedly led to improvement in flux than coagulation processes, and alum gave greater flux than M. oleifera. This was attributed to the effective removal and/or breakdown of high molecular weight (MW) organics by biofilters. BAF led to greater improvement in flux than SF, due to greater breakdown of high MW organics, and this was also confirmed by the attenuated total reflection-Fourier transform infrared spectroscopy analysis. Coagulation processes were ineffective in removing biofouling potential components, whereas both biofilters were very effective as shown by the reduction of low MW organics, biodegradable dissolved organic carbon and assimilable organic carbon contents. This study demonstrated the potential of biological pre-treatments for reducing organic and biofouling potential component and thus improving flux for the UF of lake water treatment.
The CANON process is a promising method for nitrogen removal in wastewaters with low organic carbon content like reject water. This study investigated the effect of important factors for optimization of the CANON process through inhibition of nitrite-oxidizing bacteria (NOB). In the acclimation period, complete ammonium removal and 43.3% total N removal were obtained at hydraulic retention time of 12 h, temperature of 30°C ± 0.5°C and DO equal to 7-9 mg/L. The effects of air flow rate (AFR) (representative of DO), SRT and C/N were evaluated. Air flow rate was the most important factor for controlling the process, but the effect of SRT was negligible. When AFR was increased from 100 to 500 mL/min, both ammonium removal efficiency (33-43% to 81-83%) and nitrite accumulation (nitritation, 40 mgN/L to 100-120 mgN/L) were increased, but with increasing AFR to 1000 mL/min only ammonium removal efficiency was increased and because of better condition (high DO) for NOBs, nitritation was decreased. C/N had an effect like AFR of 1000 and only increased ammonium removal efficiency and total N removal. With increasing AFR and C/N, both OUR and AUR were increased, but SVI was decreased.
The interactions within microbial, chemical and electronic elements in microbial fuel cell (MFC) system can be crucial for its bio-electrochemical activities and overall performance. Therefore, this study explored polynomial models by response surface methodology (RSM) to better understand interactions among anode pH, cathode pH and inoculum size for optimising MFC system for generation of electricity and degradation of 2,4-dichlorophenol. A statistical central composite design by RSM was used to develop the quadratic model designs. The optimised parameters were determined and evaluated by statistical results and the best MFC systematic outcomes in terms of current generation and chlorophenol degradation. Statistical results revealed that the optimum current density of 106 mA/m2 could be achieved at anode pH 7.5, cathode pH 6.3-6.6 and 21-28% for inoculum size. Anode-cathode pHs interaction was found to positively influence the current generation through extracellular electron transfer mechanism. The phenolic degradation was found to have lower response using these three parameter interactions. Only inoculum size-cathode pH interaction appeared to be significant where the optimum predicted phenolic degradation could be attained at pH 7.6 for cathode pH and 29.6% for inoculum size.
Polyhydroxybutyrate (PHB) is a natural microbial polyester produced by a variety of bacteria and archaea from renewable resources. PHB resembles some petrochemical plastics but is completely biodegradable. It is desirable to identify suitable microbial strains and develop processes that can directly use starch from agricultural wastes without commercial amylase treatment. Here, PHB production using starch from agricultural waste was developed using a newly isolated strain, Bacillus aryabhattai T34-N4. This strain hydrolyzed cassava pulp and oil palm trunk starch and accumulated up to 17 wt% PHB of the cell dry weight. The α-amylase of this strain, AmyA, showed high activity in the presence of cassava pulp starch (69.72 U) and oil palm trunk starch (70.53 U). High expression of amyA was recorded in the presence of cassava pulp starch, whereas low expression was detected in the presence of glucose. These data suggest that starch saccharification by amyA allows strain T34-N4 to grow and directly produce PHB from waste starch materials such as cassava pulp and oil palm trunk starch, which may be used as low-cost substrates.
Para-arsanilic acid (p-ASA) has been widely used in the poultry industry to promote growth and prevent dysentery. It is excreted unchanged in the manure and released into non-target sites causing organoarsenic pollution risk to the environment and living system. Therefore, simple and effective analytical strategies are demanded for determining the samples that contain p-ASA. However, direct determination of both p-ASA and ortho-arsanilic acid (o-ASA) using differential pulse cathodic stripping voltammetry (DPCSV) gives the similar voltammograms that directly hamper the analysis used by the DPCSV technique. In this study, a method to determine and differentiate p-ASA from o-ASA via diazotization and coupling reaction of the amine groups followed by the direct DPCSV determination of diazo compounds is presented. The diazotization reaction carried out at pH 1.5 and 0 ± 1°C for 10 min showed two reduction peaks in DPCSV at-70 mV and -440 mV vs. Ag/AgCl (KCl 3 M). However, when the diazotization reaction was performed at pH 12.5 and 0 ± 1°C for 40 min, a coloured azo compound was produced and the DPCSV showed only one reduction peak that appeared at -600 mV vs. Ag/AgCl (3 M of KCl). The results of this study show that only p-ASA compound gave a reduction peak, whereas o-ASA compound did not give any peak. The detection limit of p-ASA was found to be 4 × 10(-8 )M. As a result, the proposed electro-analytical technique might be a good candidate to determine and differentiate the p-ASA present in the poultry and environmental samples.
In the present study, locally isolated Rhodococcus strains were attempted as biological tools for methyl red removal, a mutagenic azo dye posing threat to the environment if left untreated. Rhodococcus strain UCC 0016 demonstrated superior methyl red-decolourizing activity of 100% after 24 h at static condition in comparison to Rhodococcus strain UCC 0008 which recorded 65% decolourization after 72 h. Optimization of physicochemical parameters at 30°C, pH 7 and supplementing glucose as the carbon source resulted in improved methyl red-decolourizing activity at static condition and reduced the time taken to achieve complete decolourization by 80%. Higher concentration of methyl red (5 g/L) was able to be decolourized completely within 10 h by adopting the technology of immobilization. The encapsulated cells of Rhodococcus strain UCC 0016 demonstrated higher substrate affinity (Km = 0.6995 g/L) and an accelerated rate of disappearance of methyl red (Vmax = 0.3203 g/L/h) compared to the free cells. Furthermore, the gellan gum beads could be reused up to nine batches without substantial loss in the catalytic activity indicating the economic importance of this protocol. Analysis of methyl red degradation products revealed no germination inhibition on Triticum aestivum and Vigna radiata demonstrating complete toxicity removal of the parent dye after biological treatment. The occurrence of new and altered peaks (UV-Vis and FTIR) further supported the notion that the removal of methyl red by Rhodococcus strain UCC 0016 was indeed through biodegradation. Therefore, this strain has a huge potential as a candidate for efficient bioremediation of wastewater containing methyl red.
Polyaniline composites consisting of carboxymethyl cellulose (CMC) have enhanced adsorption properties, but recent studies indicate that the oxidised species - dialdehyde carboxymethyl cellulose (DCMC) - outperforms CMC-based composites. However, these studies fail to study the effect of DCMC's aldehyde content and compare the composites with CMC-based composites; numerous experiments required to investigate each adsorbent for each factor limit such studies. We explored a way to study whether villi-structured polyaniline (VSPANI), its CMC composite (CMC/PANI), and its DCMC composites with 35% (DCMC(A)/PANI) and 77% (DCMC(B)/PANI) aldehyde content would be great adsorbents for removing bisphenol-A (BPA). We first customised a D-optimal screening design to alleviate the pitfalls of definitive screening design (DSD), hence estimating all the main effects: initial concentration, pH, flow rate, adsorbent amount, sample volume and type of adsorbent. We excluded CMC/PANI and DCMC(A)/PANI composites, both with low adsorption capacities of 56.57 and 57.27 mg/g from further investigation. The DSD followed to estimate all second-order effects through which we projected a response surface method (RSM) to optimise and model the active factors. Increasing the aldehyde content on the composites favoured adsorption, but there lacked evidence to suggest VSPANI and DCMC(B)/PANI differed significantly in performance. The models were numerically and graphically proven adequate, explaining 80% and 99% of the variation when predicting removal efficiency and adsorption capacity. VSPANI showed potential as an adsorbent for BPA removal with 85% removal efficiency and 129 mg/g adsorption capacity. This comprehensive approach, combining both designs, allows for sustainable investigation of multiple adsorbents and factors, minimising experimental waste.