Baseline study of methane emission from anaerobic ponds of palm oil mill effluent treatment

The world currently obtains its energy from the fossil fuels such as oil, natural gas and coal. However, the international crisis in the Middle East, rapid depletion of fossil fuel reserves as well as climate change have driven the world towards renewable energy sources which are abundant, untapped and environmentally friendly. Malaysia has abundant biomass resources generated from the agricultural industry particularly the large commodity, palm oil. This paper will focus on palm oil mill effluent (POME) as the source of renewable energy from the generation of methane and establish the current methane emission from the anaerobic treatment facility. The emission was measured from two anaerobic ponds in Felda Serting Palm Oil Mill for 52 weeks. The results showed that the methane content was between 35.0% and 70.0% and biogas flow rate ranged between 0.5 and 2.4 L/min/m(2). Total methane emission per anaerobic pond was 1043.1 kg/day. The total methane emission calculated from the two equations derived from relationships between methane emission and total carbon removal and POME discharged were comparable with field measurement. This study also revealed that anaerobic pond system is more efficient than open digesting tank system for POME treatment. Two main factors affecting the methane emission were mill activities and oil palm seasonal cropping.     

Process modeling and analysis of palm oil mill effluent treatment in an up-flow anaerobic sludge fixed film bioreactor using response surface methodology (RSM)

In this study, the interactive effects of feed flow rate (QF) and up-flow velocity (V up) on the performance of an up-flow anaerobic sludge fixed film (UASFF) reactor treating palm oil mill effluent (POME) were investigated. Long-term performance of the UASFF reactor was first examined with raw POME at a hydraulic loading rate (HRT) of 3 d and an influent COD concentration of 44300 mg/l. Extreme reactor instability was observed after 25 d. Raw POME was then chemically pretreated and used as feed. Anaerobic digestion of pretreated POME was modeled and analyzed with two operating variables, i.e. feed flow rate and up-flow velocity. Experiments were conducted based on a central composite face-centered design (CCFD) and analyzed using response surface methodology (RSM). The region of exploration for digestion of the pretreated POME was taken as the area enclosed by the feed flow rate (1.01, 7.63 l/d) and up-flow velocity (0.2, 3 m/h) boundaries. Twelve dependent parameters were either directly measured or calculated as response. These parameters were total COD (TCOD) removal, soluble COD (SCOD) removal, effluent pH, effluent total volatile fatty acid (TVFA), effluent bicarbonate alkalinity (BA), effluent total suspended solids (TSS), CH4 percentage in biogas, methane yield (Y M), specific methanogenic activity (SMA), food-to-sludge ratio (F/M), sludge height in the UASB portion and solid retention time (SRT). The optimum conditions for POME treatment were found to be 2.45 l/d and 0.75 m/h for QF and V up, respectively (corresponding to HRT of 1.5 d and recycle ratio of 23.4:1). The present study provides valuable information about interrelations of quality and process parameters at different values of the operating variables.     

Adsorption and desorption characteristics of mercury(II) ions using aminated chitosan bead

Adsorption and desorption characteristics for mercury ions using aminated chitosan bead which showed very high affinity to mercury ions were studied. The adsorption of mercury ions using aminated chitosan bead was an exothermic process since binding strength each other increased as the temperature decreased. And the adsorption of mercury ions was almost completed in 100 min at 150 rpm. In case that adsorbent dose increased, mercury uptake capacity decreased, while, removal efficiency increased. The beads were not greatly affected by the ionic strength, organic material and alkaline-earth metal ions. Mercury ions adsorbed on aminated chitosan bead were desorbed effectively about 95% by EDTA and the adsorption capacity of the recycled beads can still be maintained at 90% level at the 5th cycle.     

Adsorption of lead and humic acid on chitosan hydrogel beads

Chitosan hydrogel beads were studied for the adsorption of lead ions and humic acid from aqueous solutions to examine the adsorption behaviors and mechanisms. The experiments were carried out at room temperature with solution pH ranging from 5 to 7.5 (in near neutral pH range). Three types of batch adsorption experiments, including single species adsorption, sequential adsorption of one species after another and co-adsorption of both species, were investigated. The results show that: (1) adsorption of either species mainly results from the complexations between adsorbate and functional groups at the surface of the hydrogel beads; (2) previously adsorbed species can either act as additional binding sites for, or occupy the same binding sites as the subsequent species to be adsorbed, resulting in enhanced or retarded adsorption of the subsequent species; and (3) for co-adsorption, metal-organic interactions play a very important role in determining the extent of adsorption. It is concluded that multi-species adsorption can be significantly affected by adsorbate interactions and the understanding of these interactions needs great attention in adsorption study in the future.     

Chemical modification of chitosan and equilibrium study for mercury ion removal

To increase the uptake capacity of mercury ions, several chemical modifications of chitosan beads which are cross-linked with glutaraldehyde were performed. Among them, aminated chitosan bead prepared through chemical reaction with ethylenediamine had a high uptake capacity of about 2.3 mmol g(-1) dry mass at pH 7. The increased number of amine groups was confirmed by IR analysis and measuring the saturation capacities for adsorption of HCl. The surface condition and existence of mercury ions on the beads was confirmed by the environmental scanning electron microscope and energy dispersive X-ray spectroscopy instrumental analyses. The beads showed the characteristic of competitive sorption between mercury and hydrogen ions and it was successfully modelled by an equilibrium model.     

Removal of boron from ceramic industry wastewater by adsorption-flocculation mechanism using palm oil mill boiler (POMB) bottom ash and polymer

Boron is extensively used in the ceramic industry for enhancing mechanical strength of the tiles. The discharge of boron containing wastewater to the environment causes severe pollution problems. Boron is also dangerous for human consumption and causes organisms' reproductive impediments if the safe intake level is exceeded. Current methods to remove boron include ion-exchange, membrane filtration, precipitation-coagulation, biological and chemical treatment. These methods are costly to remove boron from the wastewater and hence infeasible for industrial wastewater treatment. In the present research, adsorption-flocculation mechanism is proposed for boron removal from ceramic wastewater by using Palm Oil Mill Boiler (POMB) bottom ash and long chain polymer or flocculant. Ceramic wastewater is turbid and milky in color which contains 15 mg/L of boron and 2000 mg/L of suspended solids. The optimum operating conditions for boron adsorption on POMB bottom ash and flocculation using polymer were investigated in the present research. Adsorption isotherm of boron on bottom ash was also investigated to evaluate the adsorption capacity. Adsorption isotherm modeling was conducted based on Langmuir and Freundlich isotherms. The results show that coarse POMB bottom ash with particle size larger than 2 mm is a suitable adsorbent where boron is removed up to 80% under the optimum conditions (pH = 8.0, dosage = 40 g bottom ash/300 ml wastewater, residence time = 1 h). The results also show that KP 1200 B cationic polymer is effective in flocculating the suspended solids while AP 120 C anionic polymer is effective in flocculating the bottom ash. The combined cationic and anionic polymers are able to clarify the ceramic wastewater under the optimum conditions (dosage of KP 1200 B cationic polymer = 100 mg/L, dosage of AP 120 C anionic polymer = 50 mg/L, mixing speed = 200 rpm). Under the optimum operating conditions, the boron and suspended solids concentration of the treated wastewater were reduced to 3 mg/L and 5 mg/L respectively, satisfying the discharge requirement by Malaysia Department of Environment (DOE). The modeling study shows that the adsorption isotherm of boron onto POMB bottom ash conformed to the Freundlich Isotherm. The proposed method is suitable for boron removal in ceramic wastewater especially in regions where POMB bottom ash is abundant.     

Optimization of hydroxyl radical production using electro‐Fenton method for chemical oxygen demand reduction in diluted palm oil mill effluent

Palm oil mill effluent (POME) is a well‐known highly polluting wastewater due to its extremely high contents of organic matter, suspended solids and nutrients. In this study, we used electro‐Fenton method to treat POME by optimizing OH? generation from hydrogen peroxide (H₂O₂) under low voltage input (1.5–6.0 V). A set of electro‐Fenton system was set up using stainless steel as the anode and graphite as the cathode. Four parameters namely retention times, concentrations of H₂O₂ as well as FeSO₄ catalyst and applied voltages were studied. The results were reflected in the form of removal efficiency of chemical oxygen demand (COD). The optimum conditions to degrade organic matter in POME were found to be in 4 h retention time with the respective H₂O₂ and FeSO₄ catalyst concentrations of 0.05 and 0.10 M, and the power input of 1.5 V. Under such conditions, the maximum COD removal efficiency achieved 94%. The electro‐Fenton treatment was found to have higher efficiency than the conventional Fenton treatment. Without the electrolysis, the COD removal efficiency of the conventional Fenton treatment was only 48%.     

Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies

Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m(2)g(-1). pH(zpc) (pH of zero point charge) of the sorbent was estimated by alkaline-titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g(-1) for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a "L2" type, while that of Pb(II) and Co(II) was of a "L1" type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10-20% of the maximum capacity was utilized in the first 30 min of interaction.     

Adsorption thermodynamic, kinetic and desorption studies of Pb2+ on carbon nanotubes

Adsorption thermodynamics of Pb2+ on carbon nanotubes has been studied at various temperatures of 280, 298 and 321 K and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (DeltaG0), standard enthalpy change (DeltaH0) and standard entropy change (DeltaS0), have been obtained. A pseudo-second-order rate model has been employed to describe the kinetic adsorption processes. Desorption studies reveal that Pb2+ can be easily removed from carbon nanotubes by altering the pH values of the solution using both HCl and HNO3, indicating that carbon nanotubes are a promising absorbent for wastewater treatment.     

Preparation and evaluation of iron–chitosan composites for removal of As(III) and As(V) from arsenic contaminated real life groundwater

A study on the removal of arsenic from real life groundwater using iron–chitosan composites is presented. Removal of arsenic(III) and arsenic(V) was studied through adsorption at pH 7.0 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir adsorption models and the various model parameters were evaluated. The monolayer adsorption capacity from the Langmuir model for iron chitosan flakes (ICF) (22.47 ± 0.56 mg/g for As(V) and 16.15 ± 0.32 mg/g for As(III)) was found to be considerably higher than that obtained for iron chitosan granules (ICB) (2.24 ± 0.04 mg/g for As(V); 2.32 ± 0.05 mg/g for As(III)). Anions including sulfate, phosphate and silicate at the levels present in groundwater did not cause serious interference in the adsorption behavior of arsenate/arsenite. The column regeneration studies were carried out for two sorption–desorption cycles for both As(III) and As(V) using ICF and ICB as sorbents. One hundred and forty-seven bed volumes of As(III) and 112 bed volumes of As(V) spiked groundwater were treated in column experiments using ICB, reducing arsenic concentration from 500 to <10 μg/l. The eluent used for the regeneration of the spent sorbent was 0.1 M NaOH. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to <10 μg/l from real life arsenic contaminated groundwater samples.     

Lightweight concrete made from oil palm shell (OPS): Structural bond and durability properties

The first part of this experimental program was to determine the structural bond properties of lightweight concrete incorporating solid waste oil palm shell (OPS) as coarse aggregate and also to compare its behaviour with other types of lightweight aggregate concretes. Other properties of OPS concrete namely the split tensile strength, modulus of rupture and modulus of elasticity were also determined. The structural bond properties were determined through pull-out test. The results showed that the experimental bond strength of OPS concrete was much higher than the design bond strength as stipulated by BS 8110. In general, the properties of OPS concrete compared well with that of other structural lightweight concretes and the results obtained encourage the use of OPS as aggregates for the production of structural lightweight concrete. The second part of the experimental program investigates the durability performance of OPS concrete through water permeability and water absorption tests.     

Biological treatment of the effluent from a bleached kraft pulp mill using basidiomycete and zygomycete fungi

Three white-rot fungi (Pleurotus sajor caju, Trametes versicolor and Phanerochaete chrysosporium) and one soft-rot fungi (Rhizopus oryzae) species confirmed their potential for future applications in the biological treatment of effluents derived from the secondary treatment of a bleached kraft pulp mill processing Eucalyptus globulus. Among the four species P. sajor caju and R. oryzae were the most effective in the biodegradation of organic compounds present in the effluent, being responsible for the reduction of relative absorbance (25-46% at 250 nm and 72-74% at 465 nm) and of chemical oxygen demand levels (74 to 81%) after 10 days of incubation. Laccase (Lac), lignin (Lip) and manganese peroxidases (MnP) expression varied among fungal species, where Lac and LiP activities were correlated with the degradation of organic compounds in the effluent treated with P. sajor caju. The first two axes of a principal component analysis explained 88.9% of the total variation among sub-samples treated with the four fungus species, after different incubation periods. All the variables measured contributed positively to the first component except for the MnP enzyme activity which was the only variable contributing negatively to the first component. Absorbances at 465 nm, LiP and Lac enzyme activities were the variables with more weight on the second component. P. sajor caju revealed to be the only species able to perform the biological treatment without promoting an increment in the toxicity of the effluent to the Vibrio fischeri, as it was assessed by the Microtox® assay. The opposite was recorded for the treatments with the other three species of fungus. EC_50-5 min values ranging between 28 and 57% (effluent concentrations) were recorded even after 10 to 13 days of treatment with P. chrysosporium, R. oryzae or with T. versicolor.     

Uptake of chloride ion from aqueous solution by calcined layered double hydroxides: equilibrium and kinetic studies

Layered double hydroxides (LDH) calcined within a certain temperature range (denoted as CLDH) have been shown to recover their original layered structure in the presence of appropriate anions. In the light of this so-called "memory effect", uptake of chloride ion from aqueous solution by calcined MgAl-CO3 LDH was investigated in batch mode. The equilibrium isotherm showed that the uptake of chloride ion by CLDH was consistent with the Langmuir and Freundlich equations and that the Langmuir model gave a better fit to the experimental data than the Freundlich model. The maximum uptake capacity of CLDH for chloride ion was 149.5 mg/g, close to the stoichiometric uptake (168 mg/g). The influence of varying pH of solution, initial chloride concentration, adsorbent quantity, and temperature on the kinetics of chloride removal has also been explored. Four kinetic models were used to fit the experimental data, and it was found that the pseudo-second-order kinetics model could be used to describe the uptake process satisfactorily. The calculated value of Ea was found to be 56.8 kJ/mol, which suggests that the process of uptake of chloride ion is controlled by the rate of reaction of chloride ion with the CLDH rather than diffusion. A mechanism for removal of chloride ion has been confirmed by X-ray diffraction, FT-IR spectroscopy and TG-MS measurements.     

黄土-粉土混合土对Pb(Ⅱ)的静平衡和动态吸附特性

竖向防污屏障是防止地下水土污染的主要屏障。天然土是屏障最主要的材料来源。以天然粉土为母土,黄土为添加剂,以重金属Pb(Ⅱ)作为污染物的代表,通过粉土-黄土混合土对Pb(Ⅱ)的静平衡吸附和动态吸附试验研究黄土作为添加剂对天然粉土的改良效果。试验考虑了黄土添加量、溶液pH值、反应时间以及重金属初始浓度等对吸附的影响。结果表明添加黄土可以有效改善天然粉土的吸附效果,混合土对Pb(Ⅱ)的吸附容量随黄土添加量的增加线性增长,添加20%黄土的混合土的吸附容量达天然粉土的2倍;添加黄土可减少混合土对重金属的吸附时间,在相同时间内减少迁移量。通过扫描电镜和XRD等手段揭示了黄土对Pb(Ⅱ)的吸附主要是方解石与Pb(Ⅱ)发生界面沉淀作用生成白铅矿;粉土对Pb(Ⅱ)的吸附主要是长石等矿物棱角处经风化水解形成的-OH基团对Pb(Ⅱ)的阳离子交换作用。黄土由于高方解石含量在对Pb(Ⅱ)的吸附方面表现突出,可以作为一种添加剂加入天然土层中,以增强屏障对重金属的吸附阻滞效果,减少环境污染。     

Simultaneous biodesulphurization and denitrification using an oil reservoir microbial culture: Effects of sulphide loading rate and sulphide to nitrate loading ratio

Biooxidation of sulphide under denitrifying conditions is a key process in control of souring in oil reservoirs and in treatment of gas and liquids contaminated with sulphide and nitrate. In this work, biooxidation of sulphide was studied using a representative culture originated from an oil reservoir. Effects of sulphide concentration, sulphide to nitrate molar ratio, and loading rates of sulphide and nitrate on their removal rates and composition of the end products were investigated. In the batch system sulphide removal rate passed through a maximum as sulphide concentration was increased from 2.1 to 16.3 mM, with the highest rate (2.06 mM h⁻¹) observed with 10.7 mM sulphide. Nitrate removal was coupled to sulphide oxidation and the highest removal rate was 1.05 mM h⁻¹. In the continuous bioreactors fed with 10 and 5, 15 and 7.5, and 20 and 10 mM sulphide and nitrate, cell wash-out occurred as dilution rate was increased above 0.15, 0.13 and 0.08 h⁻¹, respectively. Prior to cell wash-out linear increases in sulphide and nitrate removal rates were observed as loading rate was increased. The highest sulphide and nitrate removal rates of 2.0 and 0.92 mM h⁻¹ were obtained in the bioreactor fed with 15 mM sulphide and 7.5 mM nitrate at loading rates of 2.1 and 0.93 mM h⁻¹, respectively. Short residence times and high sulphide to nitrate ratios promoted the formation of sulphur, a desired end product for ex situ treatment of contaminated streams. Combination of long residence times and low sulphide to nitrate ratios, which favours formation of sulphate, is the suitable strategy for in situ removal of H₂S from oil reservoirs.     

Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic models

The isotherms and kinetics of adsorption of lead(II) and copper(II) onto a grafted silica are studied at 20 degrees C. A commercial silica is grafted with an ethylediamine derivative, N-[3-(trimethoxysilyl)propyl]-ethylenediamine. From the Langmuir isotherms, maximum adsorption capacities of the grafted silica towards Pb(II) and Cu(II) are determined (0.184 mmol Pb(II)g-1 and 0.261 mmol Cu(II)g-1) and compared to those of non-modified silica (respectively, 0.019 and 0.036 mmol g-1). Four kinetic models, i.e., pseudo-first order, pseudo-second order, Langmuir and double-exponential are applied to fit the experimental kinetic data. The kinetic parameters are determined which allow to calculate the theoretical metal uptake as a function of time. The results are discussed and indicate the best fit is obtained with the double-exponential model. A discussion on the adsorption mechanism with respect to the double-exponential model leads to two possible interpretations: the metal uptake may follow a diffusion-controlled mechanism or a two-site adsorption process.     

Removal of antibiotics from water using sewage sludge- and waste oil sludge-derived adsorbents

Sewage sludge- and waste oil sludge-derived materials were tested as adsorbents of pharmaceuticals from diluted water solutions. Simultaneous retention of eleven antibiotics plus two anticonvulsants was examined via batch adsorption experiments. Virgin and exhausted adsorbents were examined via thermal and FTIR analyses to elucidate adsorption mechanisms. Maximum adsorption capacities for the 6 materials tested ranged from 80 to 300 mg/g, comparable to the adsorption capacities of antibiotics on various activated carbons (200-400 mg/g) reported in the literature. The performance was linked to surface reactivity, polarity and porosity. A large volume of pores similar in size to the adsorbate molecules with hydrophobic carbon-based origin of pore walls was indicated as an important factor promoting the separation process. Moreover, the polar surface of an inorganic phase in the adsorbents attracted the functional groups of target molecules. The presence of reactive alkali metals promoted reaction with acidic groups, formation of salts and their precipitation in the pore system.     

Adsorption of tri- and tetra-chloroethylene from aqueous solutions on activated carbon fibers

Recently the contamination of groundwater by trichloroethylene and related compounds have become a new environmental problem. As the first step to clarify the feasibility of applying newly developed adsorbent, activated carbon fiber (ACF), to adsorption treatments of water taken from such a contaminated groundwater source, the adsorption equilibrium and the adsorption rate of trichloroethylene and tetrachloroethylene from aqueous solutions on four ACFs with different pore-size distribution were investigated. The adsorption capacities of ACFs having larger volume of micropores are larger than those of granular activated carbons (GACs) usually used at present. Also, the adsorption rate on ACFs is far more rapid in comparison with GAC adsorption because of smaller diffusion path.     

Treatment of high fluoride concentration water by MgAl-CO3 layered double hydroxides: kinetic and equilibrium studies

MgAl-CO(3) layered double hydroxides (LDHs) have been employed to treat high fluoride concentration solution. The influences of solution pH, initial fluoride concentration and other anions in the solution were investigated by a series of batch experiments. A marked decrease in the amount of adsorbed fluoride by LDHs is observed with increasing pH. The extent of fluoride removal in the presence of other anions decreases in the order HCO(3)(-)>Cl(-)>H(2)PO(4)(-)>SO(4)(2-). The equilibrium isotherm for fluoride uptake corresponds closely to the Langmuir-Freundlich (L-F) model. The maximum capacity of LDHs for fluoride ions and the Gibbs free energy (DeltaG(0)) for the defluoridation process were calculated to be 319.8+/-5.7mg/g and -9.0+/-0.66kJ/mol, respectively. The negative value of DeltaG(0) indicates the spontaneous nature of the treatment process. Four kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second order, the modified multiplex and the double exponential models. It was found that the modified multiplex model, involving a rapid first order step and a slow second order step most closely described the kinetics. The activation energies for the two steps are 37.2+/-5.26 and 72.6+/-4.52kJ/mol, respectively, suggesting that the rapid step is controlled by diffusion processes, whilst the second step is controlled by the reaction of fluoride with the LDHs.