Influence Of Ph And Initial Sludge Concentration On Anaerobic Digestion Of Waste Activated Sludge

Although anaerobic digestion is a common process for treatment of sludge, the digestion rate remains low. Hydrolysis is the first step of anaerobic digestion process and generally is considered to be the rate-limiting step for the overall digestion process. Hence, improvement in the hydrolysis rate is needed to enhance anaerobic digestion of sludge. Chemical hydrolysis can be used as an alternative as it could improve the digestion performance of the sludge. However, hydrolysis process relies on enzymes excreted by the fermentative acidogens, and is strongly pH dependent. Consequently, determination of the optimum pH of sludge digestion is essential and required. In spite of pH, initial concentration of sludge is also an important factor that influences the anaerobic digestion performance of sludge. However, concentrations of total suspended solids (TSS) at a secondary clarifier and a thickener are 1.0% and 4.0% TSS, respectively.This study focuses on a laboratory-scale research on improvement of anaerobic digestion of waste activated sludge (WAS) which was performed by chemical hydrolysis using 0.5 M H2SO4 and 4.0 M NaOH at temperature of 29 ± 1 °C and agitation of 150 rpm. The research was conducted in two phases: the first phase investigated the effect of pH at pH 6.00, 7.00, 8.00, 9.00 and uncontrolled pH on the digestion performance at initial concentration of 4.0% TSS; the second phase investigated and compared the performance of anaerobic digestion at initial concentrations of 1.0% and 4.0% TSS at the optimum pH which was determined from the first phase. Subsequently, determination of kinetic parameters and followed by developments of mathematical models and computer programs were performed at both phases. Significantly higher average removals, removal rates and rate constants of TSS, volatile suspended solids (VSS), total chemical oxygen demand (TCOD) and particulate chemical oxygen demand (PCOD) at controlled pH compared to that at uncontrolled pH. The average removals and removal rates at uncontrolled pH could be improved by 1 to 4 times by controlled pH. Meanwhile rate constants could be improved by 1 to 7. The highest average removal, removal rate and rate constant were found at pH 6.00 followed by pH 8.00, 7.00, 9.00 and uncontrolled pH. The results also indicated that the optimum pH was at pH 6.00. The improvement of sludge digestion was attributed to the enhancement of sludge solubilisation by the chemical hydrolysis as higher soluble chemical oxygen demand (SCOD) concentration was observed at the controlled pH.There was no significant difference in rate constant and removal of the sludge. However, significantly higher average removal rates of TSS, VSS, TCOD and PCOD were achieved at initial concentration of 4.0% TSS. The improvement of the average removal rates of TSS, VSS, TCOD and PCOD was 2.5 to 3.4 times over that at initial concentration of 1.0% TSS giving rise to a higher digestion performance at initial concentration of 4.0% TSS. The experimental results fitted well in first-order models in both phases. High relationships between simulated and experimental results were obtained from both phases experiments with correlation coefficients (R2) ranging from 0.80 to 0.99. Hence, the developed mathematical models can be considered as a useful tool for predicting the concentrations remaining and removals of TSS, VSS, TCOD and PCOD as well as digestion time

Membrane Filtration Application in Pre-Treatment of Crude Palm Oil

The pre-treatment of crude palm oil results in loss of oil and a contaminated effluent. The objective of this research is to study the effectiveness of membrane filtration in the pre-treatment of crude palm oil for removal of phospholipids from c rude palm oil. Initial investigation with a 25,000 molecular weight cut-off, polysulfone membrane did not yield any s ignificant results. Hence, it was decided to use a PCI module, which was equipped with polyethersulfone membranes having a molecular weight cut-o ff of 9,000 (type ES209). The membrane process was carried out at 26 bar pressure and a temperature of 63±2°C. The sample, permeate and retentate were analysed for various quality parameters including phosphorus content, carotene content, free fatty acid, colour and volatile matter. The membrane e ffectively removed phospholipids resulting in a permeate with a phosphorus content of less than 0.3 ppm. The percentage removal of phosphorus was 96.4% and can be cons idered significant. Lovibond colour was reduced from 27R 50Y to 20R 30Y whereas the percentage removal of carotene was 17.5%. The removal of colour was considered good but removal of carotene was considered insignificant by the membrane. Free fatty acids and volatile matter were not removed. Typical of membrane operations, the permeate flux decreased with time and must be improved in order to be adopted on an industrial scale. Membrane separation using polyethersulfone type was found to have a good potential in crude palm oil degumming. However, an appropriate method has to be developed to clean the membranes

Sorption kinetics of Zn (II) ion by thermally treated rice husk

Agricultural wastes such as orange peels, tea leave waste, rice husk and corn cobs have been widely studied as sorbents for heavy metal ion removal from various wastewaters. In order to understand their sorption mechanism, the adsorption kinetics is studied. This report describes the kinetics study of a thermally treated rice husk to adsorb Zn (II) ion from an aqueous solution. The adsorbent was obtained by heating the rice husk in a furnace at 500°C for two hours. Increase the contact period improved percentage of the removal of Zn (II) ion until an equilibrium was reached. The data obtained showed that the adsorption of Zn (II) ion by thermally treated rice husk obeyed pseudo-second order kinetics model, which is in agreement with chemisorption as the rate limiting mechanism

Surface modification of multi-walled carbon nanotube using double-chained quaternary ammonium bromide

Modification of multi-walled carbon nanotube (MWCNT) plays an important role to produce MWCNT crossbreeds that may be useful for exploration of new materials. In this report, characterization of dimethyl dioctadecylammonium bromide (DDOAB) modified multi-walled carbon nanotube (Mo-MWCNT) using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) is described. FTIR shows the presence of both aliphatic (CH stretching and CH bending) and ammonium (CN stretching) groups from DDOAB and the existence of C=C aromatic functional group from the structure of MWCNT in Mo-MWCNT spectra. This result was supported by TGA result which suggests that there are weight losses due to the degradation of DDOAB (between 250 °C to 500 °C) in the product. In addition, XRD pattern remain after modification suggesting attachment of MWCNT and DDOAB occurs at the surface of MWCNT

Immobilization of mutant phosphotriesterase on fuller’s earth enhanced the stability of the enzyme

Immobilization is a method for making an enzyme more robust in the environment, especially in terms of its stability and reusability. A mutant phosphotriesterase (YT PTE) isolated from Pseudomonas dimunita has been reported to have high proficiency in hydrolyzing the Sp and Rp-enantiomers of organophosphate chromophoric analogs and therefore has great potential as a decontamination agent and biosensor. This work aims to investigate the feasibility of using Fuller’s earth (FE) as a YT PTE immobilization support and characterize its biochemical features after immobilization. The immobilized YT PTE was found to show improvement in thermal stability with a half-life of 24 h compared to that of the free enzyme, which was only 8 h. The stability of the immobilized YT PTE allowed storage for up to 4 months and reuse for up to 6 times. The immobilized YT PTE showed high tolerance against all tested metal ions, Tween 40 and 80 surfactants and inorganic solvents. These findings showed that the immobilized YT PTE became more robust for use especially with regards to its stability and reusability. These features would enhance the future applicability of this enzyme as a decontamination agent and its use in other suitable industrial applications

Adsorption of carbon dioxide by reusing drinking water treatment plant sludge

Cost effective, easy to use and regenerate could be the desired properties of an adsorbent. Reusing of waste material as CO2 adsorbent can be a good alternative for solving the problem of waste disposal as well. Thus, in this study, aluminium-based drinking water treatment plant sludge as carbon dioxide adsorbent was reused. The sludge collected from a local drinking water treatment plant. It was dried and characterized using scanning electron microscope-energy disperse X-ray (SEM-EDX), Fourier transform infrared spectrometer (FTIR) and thermogravimetric analysis (TGA). Investigations of the effects of temperature, flow rate, concentration of CO2 and adsorbent dosage on CO2 adsorption capacity were performed using a fixed bed column at a pressure of 1 bar. The maximum capacity of 32.56 mg/g was found which was higher than that of some reported adsorbents

Preparation and characterization of sodium lauryl ether sulphate modified layered double hydroxides

Layered double hydroxides (LDHs) has attracted much attention of many industrialists as well as academicians as these materials can be used as catalysts, adsorbents, anion exchangers, stabilizers and fillers for polymers. The materials which consist of divalent and trivalent cations, and anions are nontoxic and easy to prepare. In addition, the exchangeability of their anions makes them easy to be modified to increase their hydrophobicity property through anion exchange process using long chain surfactant anions. In this study, sodium lauryl ether sulphate (SLES) modified LDHs was prepared by coprecipitation of LDHs and followed SLES ions modification via ion exchange process. Intercalations of the anions into the LDHs layers were confirmed by X-ray diffraction analysis. The presence of functional groups before and after modification was studied by FTIR spectrometry. Thermalgravitmeric analysis also was carried out to determine the amount of surfactant intercalated into LDHs

An electrochemical sensor based on gold nanoparticles-functionalized reduced graphene oxide screen printed electrode for the detection of pyocyanin biomarker in Pseudomonas aeruginosa infection

Multidrug resistant Pseudomonas aeruginosa (P. aeruginosa) is known to be a problematic bacterium for being a major cause of opportunistic and nosocomial infections. In this study, reduced graphene oxide decorated with gold nanoparticles (AuNPs/rGO) was utilized as a new sensing material for a fast and direct electrochemical detection of pyocyanin as a biomarker of P. aeruginosa infections. Under optimal condition, the developed electrochemical pyocyanin sensor exhibited a good linear range for the determination of pyocyanin in phosphate-buffered saline (PBS), human saliva and urine at a clinically relevant concentration range of 1–100 μM, achieving a detection limit of 0.27 μM, 1.34 μM, and 2.3 μM, respectively. Our developed sensor demonstrated good selectivity towards pyocyanin in the presence of interfering molecule such as ascorbic acid, uric acid, NADH, glucose, and acetylsalicylic acid, which are commonly found in human fluids. Furthermore, the developed sensor was able to discriminate the signal with and without the presence of pyocyanin directly in P. aeruginosa culture. This proposed technique demonstrates its potential application in monitoring the presence of P. aeruginosa infection in patients

Response surface methodology for optimization of nitrocellulose preparation from nata de coco bacterial cellulose for propellant formulation

Nitrocellulose (NC) has garnered significant interest among researchers due to its versatile applications, contingent upon the degree of nitration that modifies the cellulose structure. For instance, NC with a high nitrogen content, exceeding 12.5%, finds utility as a key ingredient in propellant formulations, while variants with lower nitrogen content prove suitable for a range of other applications, including the formulation of printing inks, varnishes, and coatings. This communication aims to present the outcomes of our efforts to optimize the nitration reaction of bacterial cellulose to produce high-nitrogen-content NC, employing the response surface methodology (RSM). Our investigation delves into the influence of the mole ratio of sulfuric and nitric acids, reaction temperature, and nitration duration on the nitrogen content of the resultant products. Utilizing a central composite design (CCD), we identified the optimal conditions for NC synthesis. Analysis of variance (ANOVA) underscored the substantial impact of these reaction conditions on the percentage of nitrogen content (%N) yield. By implementing the predicted optimal conditions—namely, a H2SO4:HNO3 mole ratio of 3:1, a reaction temperature of 35 °C, and a reaction period of 22 min—we successfully produced NC with a nitrogen content of 12.64%. Characterization of these products encompassed elemental analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM)

Microbial phosphotriesterase: structure, function, and biotechnological applications

The role of phosphotriesterase as an enzyme which is able to hydrolyze organophosphate compounds cannot be disputed. Contamination by organophosphate (OP) compounds in the environment is alarming, and even more worrying is the toxicity of this compound, which affects the nervous system. Thus, it is important to find a safer way to detoxify, detect and recuperate from the toxicity effects of this compound. Phosphotriesterases (PTEs) are mostly isolated from soil bacteria and are classified as metalloenzymes or metal-dependent enzymes that contain bimetals at the active site. There are three separate pockets to accommodate the substrate into the active site of each PTE. This enzyme generally shows a high catalytic activity towards phosphotriesters. These microbial enzymes are robust and easy to manipulate. Currently, PTEs are widely studied for the detection, detoxification, and enzyme therapies for OP compound poisoning incidents. The discovery and understanding of PTEs would pave ways for greener approaches in biotechnological applications and to solve environmental issues relating to OP contamination