It is the first time to do investigation the reliability and validity of thirty kinetic and isotherm models for describing the behaviors of adsorption of silver nanoparticles (AgNPs) onto different adsorbents. The purpose of this study is therefore to assess the most reliable models for the adsorption of AgNPs onto feasibility of an adsorbent. The fifteen kinetic models and fifteen isotherm models were used to test secondary data of AgNPs adsorption collected from the various data sources. The rankings of arithmetic mean were estimated based on the six statistical analysis methods of using a dedicated software of the MATLAB Optimization Toolbox with a least square curve fitting function. The use of fractal-like mixed 1, 2-order model for describing the adsorption kinetics and that of Fritz-Schlunder and Baudu models for describing the adsorption isotherms can be recommended as the most reliable models for AgNPs adsorption onto the natural and synthetic adsorbent materials. The application of thirty models have been identified for the adsorption of AgNPs to clarify the usefulness of both groups of the kinetic and isotherm equations in the rank order of the levels of accuracy, and this significantly contributes to understandability and usability of the proper models and makes to knowledge beyond the existing literatures.
Temporal changes of Ephemeroptera, Plecoptera and Trichoptera (EPT) communities were investigated at the study area of Gunung Pulai Recreational Forest, Johor, Malaysia. Taxa diversity were also studied to determine the seasonality impact on certain benthic communities. Sampling of aquatic insects were carried out from November 2012 to July 2013 using rectangular dip net. As a result, more EPT were found during the dry season (1533 individuals) compared to wet season (321 individuals). Concomitantly, higher diversity was also recorded in the dry season. Among these three investigated orders, Trichoptera represented the most diverse community with three families recorded, followed by Plecoptera (2 families) and Ephemeroptera (1 family). Caddisfly family Hydropsychidae were found to be abundant in the study area. Therefore, seasonality impact on EPT assemblage at Gunung Pulai Recreational Forest is extremely evident.
Associated with the continuing increase of construction activities such as infrastructure projects, commercial buildings and housing programs, Bangladesh has been experiencing a rapid increase of construction and demolition (C&D) waste. Till now, the generation rate of C&D waste has not been well understood or not explicitly documented in Bangladesh. This study aims to provide an approach to estimate C&D waste generation using waste generation rates (WGR) through regression analysis. Furthermore, analyses the economic benefit of recycling C&D waste. The results revealed that WGR 63.74 kg/m2 and 1615 kg/m2 for construction and demolition activities respectively. Approximately, in financial year (FY) 2016, 1.28 million tons (0.149 construction and 1.139 demolition) waste were generated in Dhaka city, of which the three largest proportions were concrete (60%), brick/block (21%) and mortar (9%). After collection they were dumped in either landfills or unauthorized places. Therefore, it can be summarized as: waste is a resource in wrong place. The results of this study indicate that rapid urbanization of Dhaka city would likely experience the peak in the generation of C&D waste. This paper thus designates that C&D waste recycling is an entrepreneurial activity worth venturing into and an opportunity for extracting economic and environmental benefits from waste. The research findings also show that recycling of concrete and brick waste can add economic value of around 44.96 million USD. In addition, recycling of C&D waste leads to important reductions in CO2 emissions, energy use, natural resources and illegal landfills. Therefore, the findings of WGR and economic values provide valuable quantitative information for the future C&D waste management exercises of various stakeholders such as government, industry and academy.
The current status of silver nanoparticles (AgNPs) in the water environment in Malaysia was examined and reported. For inspection, two rivers and two sewage treatment plants (STPs) were selected. Two activated carbons derived from oil palm (ACfOPS) and coconut (ACfCS) shells were proposed as the adsorbent to remove AgNPs. It was found that the concentrations of AgNPs in the rivers and STPs are in the ranges of 0.13 to 10.16 mg L-1 and 0.13 to 20.02 mg L-1, respectively, with the highest concentration measured in July. ACfOPS and ACfCS removed up to 99.6 and 99.9% of AgNPs, respectively, from the water. The interaction mechanism between AgNPs and the activated carbon surface employed in this work was mainly the electrostatic force interaction via binding Ag+ with O- presented in the activated carbon to form AgO. Fifteen kinetic models were compared statistically to describe the removal of AgNPs. It was found that the experimental adsorption data can be best described using the mixed 1,2-order model. Therefore, this model has the potential to be a candidate for a general model to describe AgNPs adsorption using numerous materials, its validation of which has been confirmed with other material data from previous works.
Biochemical products have been widely used for treatment of various types of wastewater. The treatment processes with the addition of biochemical products are quite attractive because of their simplicity, minimal use of equipment, they are environmentally friendly and are suitable for the removal of organic pollutants. The purpose of these products is to enhance the activities of beneficial microbes in order to improve treatment performance. This study was carried out to determine the potential of applying biochemical products in assisting and improving the performance of sewage treatment plants. In this study, four biochemical products, namely: Zeolite, Bio-C, Eco-B and Was-D, were applied to the sewage treatment plant. Analyses were carried out on several water quality parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), oil & grease (O&G), phosphorus (P), ammoniacal nitrogen (AN) and sludge thickness (ST). From the results obtained, it can be seen that the overall performance of the treatment plant improved with most of the parameters studied were found to fulfill the DOE Standard B requirements. The performance of Bio-C was found to give better results than other products.
Influence of deforestation on biodiversity of aquatic organisms was investigated in a stream in the Ulu Sedili Forest Reserve. The stream was monitored five (5) times from December 2011 until December 2012 with 2-month intervals. Sampling of benthic communities was carried out using rectangular dip net while water quality study using a YSI ProPlus meter and the rest were done in the laboratory. Physicochemical parameters and water quality index (WQI) calculation showed no significant difference among the investigated events. WQI classified the Berasau River between Class II (good) to III (moderate) of river water quality. In total, 603 individuals representing 25 taxa that were recorded with Decapods from genus Macrobrabchium were widely distributed. Several intolerant taxa, especially Ephemeroptera and Odonata, were also observed in this river. According to Pearson's correlation analysis, the richness and diversity indices were generally influenced by water quality parameters represented by WQI (P
Anaerobic digestion for palm oil mill effluent (POME) is widely known for its potential in biogass production. In this study, the potential of using cattle manure for biogas production in complete mix anaerobic bioreactor was investigated using POME at unregulated pH and temperature. Two identical bioreactors were used in this study; namely R1 and R2 fed with cattle manure without and with POME as inoculum, respectively. Both bioreactors were allowed for five days to run in batch mode followed by semi continuous operations at HRT of 20 days. R2 produced 41% methane content compared to 18% produced in R1. A better COD percentage reduction of 45% was found in R2 which was operated with POME as inoculum compared to R1 with 35%. These results indicated that POME as inoculum has an influence on the start-up time and the rate of biogas produced.This findings will help in waste reduction.
This study aimed to produce polyhydroxyalkanoates (PHAs) from organic wastes by mixed bacterial cultures using anaerobic-aerobic fermentation systems. Palm oil mill effluent (POME) was used as an organic source, which was cultivated in a two-step-process of acidogenesis and acid polymerization. POME was operated in a continuous flow anaerobic reactor to access volatile fatty acids (VFAs) for PHAs production. During fermentation, VFA concentration was produced in the range of 5 to 8 g/L and the COD concentration reduced up to 80% from 65 g/L. The VFA from anaerobic fermentation was then utilised for PHA production using a mixed culture in availability of aerobic bioreactor. Production of PHAs was recorded high when using a high volume of substrates because of the higher VFA concentration. Even though the maximum PHA content was observed at only 40% of the cell dried weight (CDW), their production and performance are significant in mixed microbial culture.
The developed microbial granules containing photosynthetic pigments had successfully achieved approximately 18-21% of carbon dioxide (CO2) removal in POME for one complete SBR cycle. Also, the granules had reached CO2 removal at 15-29% within 24h and removal of 25% after 5 days. Both results were inconsistent possibly due to the slow mass transfer rate of CO2 from gas to liquid as well as the simultaneous effect of CO2 production and respiration among the microbes. Furthermore, results showed the removal of CO2 from air increases proportionally with the CO2 removed in liquid. The CO2 biofixation of granules attained was approximately 0.23g/L/day for a week. Using the regression model, the removal of CO2 between liquid and gas, CO2 biofixation rate were highly correlated with the treatment time. A statistically significant relationship was obtained between CO2 concentration in liquid, biomass productivity and treatment time for the CO2 biofixation rate of the granules.
High PHA production and storage using palm oil mill effluent (POME) was investigated using a laboratory batch Bio-PORec® system under aerobic-feeding conditions. Results showed that maximum PHA was obtained at a specific rate (q(p)) of 0.343 C-mol/C-molh when air was supplied at 20 ml/min. The PHA yield was found to be 0.80 C-mol/C-mol acetic acid (HAc) at microaerophilic condition and the mass balance calculation showed that PHA production increased up to 15.68±2.15 C-mmol/cycle. The experiments showed that short feeding rate, limited requirements for electron acceptors (e.g. O(2), NO(3)) and nutrients (N and P) showed lower tendency of glycogen accumulation and contributed more to PHA productivity.
Green procedure for synthesizing silver nanoparticles (AgNPs) is currently considered due to its economy and toxic-free effects. Several existing works on synthesizing AgNPs using leaves extract still involve the use of physical or mechanical treatment such as heating or stirring, which consume a lot of energy. To extend and explore the green extraction philosophy, we report here the synthesis and antibacterial evaluations of a purely green procedure to synthesize AgNPs using Carica papaya, Manihot esculenta, and Morinda citrifolia leaves extract without the aforementioned additional treatment. The produced AgNPs were characterized using the ultraviolet-visible spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and antibacterial investigations. For antibacterial tests, two bacteria namely Escherichia coli and Bacillus cereus were selected. The presently employed method has successfully produced spherical AgNPs having sizes ranging from 9 to 69 nm, with plasmonic characteristics ranging from 356 to 485 nm, and energy-dispersive X-ray peak at approximately 3 keV. In addition, the smallest particles can be produced when Manihot esculenta leaves extract was applied. Moreover, this study also confirmed that both the leaves and synthesized AgNPs exhibit the antibacterial capability, depending on their concentration and the bacteria type.
Aerobic granulation is increasingly used in wastewater treatment due to its unique physical properties and microbial functionalities. Granule size defines the physical properties of granules based on biomass accumulation. This study aims to determine the profile of size development under two physicochemical conditions. Two identical bioreactors namely Rnp and Rp were operated under non-phototrophic and phototrophic conditions, respectively. An illustrative scheme was developed to comprehend the mechanism of size development that delineates the granular size throughout the granulation. Observations on granules' size variation have shown that activated sludge revolutionised into the form of aerobic granules through the increase of biomass concentration in bioreactors which also determined the changes of granule size. Both reactors demonstrated that size transformed in a similar trend when tested with and without illumination. Thus, different types of aerobic granules may increase in size in the same way as recommended in the aerobic granule size development scheme.