- Decolorization of Malachite green dye from wastewater by Populus
deltoides: three-level Box–Behnken design optimization,
equilibrium, and kinetic studies
- Authors: Afsaneh Shahbazi; Farnoosh Bagheri Zonoz
Abstract: Decolorization of Malachite green in aqueous solution by adsorption onto Populus deltoides sawdust (PSD) was optimized through a four-factor, three-level Box–Behnken design in response surface methodology. The influences of four independent variables such as initial pH of solution (3–7), dye concentration (50–300 mg/L), adsorbent dose (0.2–2 g/L), and temperature (23–50 °C) were studied to optimize the condition of dye removal. A natural log transformation was suggested by the Box–Cox plot in order to enhance the model significance. Regression analysis showed good fit of the experimental data to the second-order polynomial model with high coefficient of determination values (R
2 = 0.996; R
2 = 0.9913; R
2 = 0.9769), F-value of 213.03, and p-value of <0.0001 (α = 0.05). Under optimum values of all the four variables, viz., pH of 6.02, initial dye concentration of 262.6 mg/L, adsorbent dose of 0.23 g/L and temperature of 30.3 °C, the maximum uptake (q
e) was noted to be 920.9 mg/g. The experimental equilibrium adsorption data were fitted well to the Langmuir isotherm model (R
2 = 0.9949). Kinetic studies revealed that adsorption followed pseudo-second order. It was found that PSD is suitable for reuse four times in successive adsorption-desorption cycles with loss of 25.2% in adsorption capacity.
- Assessment of biologically active GAC and complementary technologies for
gray water treatment
- Authors: Laura Ward; Martin Page, John Jurevis, Andrew Nelson, Melixa Rivera, Margaret Hernandez, Mark Chappell James Dusenbury
Abstract: The reuse of gray water for applications ranging from irrigation to showering is a viable means to reduce net water demand when water supplies are stressed. The objective of this study was to investigate the treatment of gray water using biologically active granular-activated carbon (GAC) and complementary technologies. Technologies were challenged individually or in combination using a synthetic gray water formulation based on NSF/ANSI Standard 350. Specific technologies included: GAC; biologically active GAC (BAC); a newly developed intermittently operated BAC (IOBAC) process; ion exchange (IX); coagulation with a cationic polymer; microfiltration; ultrafiltration (UF); and multi-barrier combinations thereof. For control of organic contaminants such as surfactants, BAC and IOBAC performed well over test periods as long as 6 months. Combinations of IOBAC treatment with coagulation pretreatment and UF post-treatment resulted in sustained chemical oxidant demand and turbidity value reductions in excess of 90 and 99.5%, respectively. Such an approach would be useful for gray water treatment for low tier applications like irrigation or toilet flushing, or as a pretreatment system upstream of reverse osmosis (RO) membranes and/or advanced oxidation processes for high tier reuse applications such as showering.
- Solar disinfection and lime stabilization processes for reduction of
pathogenic bacteria in sewage effluents and biosolids for agricultural
purposes in Yemen
- Authors: Adel A. S. Al-Gheethi; Norli Ismail, A. N. Efaq, J. D. Bala Ramzy M. A. Al-Amery
Abstract: Yemen is the least advanced country among Middle Eastern countries in sewage reuse and safety control. The current sewage effluent quality in Yemen is generally poor as none of the existing sewage treatment plants produces effluents that comply with the effluent quality regulations. There is no plan to build tertiary treatment systems. However, the oxidation and stabilization ponds are considered most appropriate for the warm climate conditions in the country. Sewage effluents and biosolids generated from these ponds are used extensively for agricultural purposes. This review discusses the potential use of solar disinfection (SODIS) and lime treatment for the reduction of pathogens in sewage effluents and biosolids before reuse. SODIS and lime treatment are natural processes, simple, easily implemented, produce non-toxic by-products and are low cost. The merits of these processes are enormous, and they are suitable for application in developing countries such as Yemen.
- Prospects of desalination for irrigation water in the Sultanate of Oman
- Authors: Salem Ali Al-Jabri; Mushtaque Ahmed B. S. Choudri
Abstract: The most limiting factor for the agricultural sector in the Sultanate of Oman is a lack of water, and security of supply in terms of both quantity and quality. Salinization of both soils and groundwater systems along the coastal strip of Al-Batinah has placed a substantial burden on farmers regarding crop selection and, therefore, farm profitability. Desalination of brackish and seawaters might be an attractive option to sustain salt-affected lands in the Sultanate, particularly given that recent advances in desalination technologies have reduced energy and running cost requirements. This review is a summary of the international experience on desalination for irrigation water; the opportunities and challenges of the use of this technology for sustaining agriculture in arid environments; and the outcome of a survey that explores the extent of the use of desalination for providing irrigation water on the Al-Batinah coast, Oman. The main challenges for adopting this technology for agriculture are the initial cost of desalination units and the cost of environmentally sustainable disposal of reject water. However, there is a need for more applied research efforts to minimize the detrimental impact of disposal of reject water on the environment, long-term impact of desalinated water on agricultural soils as well as cost and benefit analysis of the technology.
- Augmentation of surface water sources from spatially distributed rainfall
in Saudi Arabia
- Authors: Muhammad Al-Zahrani; Shakhawat Chowdhury Amin Abo-Monasar
Abstract: This study investigated the rainfall patterns, spatial variability, surface runoff generation and dam requirements in the southwestern region of Saudi Arabia. The region was divided into four areas Asir, Jazan, Al-Baha and the Red Sea Coast. Surface runoff was estimated for eight scenarios considering the runoff coefficients of 0.05–0.70, resulting in 203–2,835 million cubic meters (MCM) of runoff per year in this region. The runoff in the Asir, Jazan, Al-Baha and the Red Sea Coast were estimated to be in the ranges of 88–1,230, 53–738, 32–443 and 30–425 MCM per year, respectively. The capacities of the existing dams in Asir, Jazan and Al-Baha are approximately 373, 194 and 31 MCM, respectively, while the coast does not have any dam. A significant fraction of runoff is likely to be lost in each scenario of assessment. Water resources may be augmented through construction of new dams and/or wells in appropriate locations. However, better understanding is advisable on locations, water availability, surface evaporation in wadies and reservoirs, accumulation of solids in dam/reservoirs, hydraulic conductivity, economic burdens and national policy.
- Water reuse system in Xi'an Municipality of China
- Authors: Rong Chen; Xiaochang Wang Yanzheng Liu
Abstract: A water reuse system was formulated for the Xi'an International Metropolitan Urban Planning Project, with the aim of mitigating water stress in the central city of Xi'an, China in 2020. The main reuse purposes of the reclaimed water were agriculture, industry, municipal, ecological, and indoor uses. A wastewater reuse potential capacity of 427.2 × 106 m3/yr was deduced by analyzing the water demand for the different reuse purposes. This reuse capacity makes significant contribution to increasing the total urban water supply capacity and mitigating the water shortage problems imposed by the process of urbanization. A supply scheme for the reclaimed water was configured, which comprised the reclaimed water sources, water supply service areas, and the main reuse purposes. As a result, a wastewater treatment plants (WWTPs)-centered reclaimed water supply system was formed, and the main reuse purposes of the 15 WWTPs and their service districts were defined. Through an economic analysis, the feasibility and benefits of the water reuse system were ascertained. Overall, this study provided the theoretical basis and implementation strategies for a system configuration of water reuse in Xi'an City and also contributed to solving the water-deficiency problems associated with the rapidly developing urban areas in China.
- Evaluation of Cryptosporidium oocyst and
Giardia cyst removal efficiency from urban and
slaughterhouse wastewater treatment plants and assessment of cyst
viability in wastewater effluent samples from Tehran, Iran
- Authors: Kareem Hatam-Nahavandi; Mehdi Mohebali, Amir-Hossein Mahvi, Hossein Keshavarz, Khadijeh Khanaliha, Fatemeh Tarighi, Mohammad-bagher Molaei-Rad, Tahereh Rezaeian, Sorour Charehdar, Mahbobeh Salimi, Shohreh Farnia Mostafa Rezaeian
Abstract: Five municipal and domestic wastewater treatment plants, most of which had secondary treatment systems formed by activated sludge, were studied during 2013–2014 in Tehran. The study was done in order to evaluate their efficiency in terms of removal of Cryptosporidium and Giardia by (oo)cyst recovery in effluent samples using immunofluorescence with monoclonal antibodies. Results showed that mean concentrations of cysts in the influent samples always outnumbered mean concentrations of oocysts (883.3 ± 4,16.7–3,191.7 ± 1,067.2 versus 4.8 ± 6.2–83.8 ± 77.3 (oo)cysts/L), and that lower concentrations of (oo)cysts were recorded in summer, and higher levels in autumn, and that the difference was statistically significant (t-test, P <0.05) only in wastewater from slaughterhouses. Results for removal percentages of all the plants ranged from 76.7 to 92.1% for cysts and from 48.9 to 90.8% for oocysts. There was more reduction of (oo)cysts at the urban treatment plant by activated sludge-A2O-sand filtration than at plants with conventional activated sludge and activated sludge-trickling filter, however, this difference was not statistically significant for cysts and oocysts (ANOVA, P > 0.05). Infections in mice inoculated with cysts obtained from urban wastewater effluent demonstrated presence of infectious Giardia cysts. Results demonstrate limited efficiency of conventional wastewater treatment processes at physico-chemical removal of (oo)cysts.
- Kinetics and equilibrium studies for removal of fluoride from underground
water using cryptocrystalline magnesite
- Authors: Vhahangwele Masindi; Wilson Mugera Gitari Tholiso Ngulube
Abstract: In the present study, the defluoridation capabilities and adsorption mechanisms of cryptocrystalline magnesite were evaluated. All experiments were done by batch procedure. Conditions assessed include time, dosage, concentration, pH and the effects of competing ions. Optimum defluoridation conditions were observed to be 20 g/L magnesite, 2:100 solid:liquid ratio, 20 min of agitation and 60 mg/L fluoride concentration. Adsorption of fluoride by magnesite was observed to be independent of pH. Cryptocrystalline magnesite showed >99% efficiency for fluoride removal. Adsorption kinetics fitted better to a pseudo-second order than a pseudo-first order thus confirming chemisorption. Adsorption data fitted better to a Langmuir than a Freundlich adsorption isotherm thus confirming monolayer adsorption. Cryptocrystalline magnesite successfully removed excess fluoride from aqueous solution to below Department of Water Affairs and Forestry water quality guidelines. As such, this material can be used for a point source defluoridation technique in rural areas and households in South Africa and other developing countries. Based on comparison studies, cryptocrystalline magnesite proved to have high adsorption capacity for fluoride removal and can be used as a substitute for conventional treatment methods.
- The potential of ultrasonic membrane anaerobic systems in treating
- Authors: N. H. Abdurahman; Y. M. Rosli, N. H. Azhari Hayder A. Bari
Abstract: Direct discharge of slaughterhouse wastewater causes serious environmental pollution due to its high chemical oxygen demand (COD), total suspended solids (TSS) and biochemical oxygen demand. In this study, an ultrasonic-assisted membrane anaerobic system was used as a novel method for treating slaughterhouse wastewater. Six steady states were achieved, using concentrations of 7,800–13,620 mg/l for mixed liquor suspended solids and 5,359–11,424 mg/l for mixed liquor volatile suspended solids (MLVSS). Kinetic equations were used to describe the kinetics of treatment at organic loading rates of 3–11 kg COD/m3/d. The removal efficiency of COD was 94.8–96.5% with hydraulic retention times of 308.6–8.7 days. The growth yield coefficient was found to be 0.52 g VSS/g. COD was 0.21 d−1 and methane gas production rate was 0.24–0.56 l/g COD/d. Steady-state influent COD concentrations increased from 8,000 mg/l in the first steady state to 25,400 mg/l in the sixth steady state. The minimum solids retention time, θc
min obtained from the three kinetic models was 6–14.4 days. The k values were 0.35–0.519 g COD/g VSS.d and μ
max values were between 0.26 and 0.379 d−1. The solids retention time decreased from 600 to 14.3 days. The complete treatment reduced the COD content and its removal efficiency reached 94.8%.
- Development and identification of a multi-species water quality model for
reclaimed water distribution systems
- Authors: Shun Li; Fu Sun, Siyu Zeng, Xin Dong Pengfei Du
Abstract: With the rapid development of a centralized wastewater reuse scheme in China, water quality concerns arise considering the long-distance transport of reclaimed water in distribution systems from wastewater treatment plants to points of use. To this end, a multi-species water quality model for reclaimed water distribution systems (RWDSs) was developed and validated against the data from part of a full-scale RWDS in Beijing. The model could simulate organics, ammonia nitrogen, residual chlorine, inert particles, and six microbial species, i.e. fecal coliforms, Enterococcus spp., Salmonella spp., Mycobacterium spp., and other heterotrophic and autotrophic bacteria, in both the bulk liquid and the biofilm. Altogether, 56 reaction processes were involved, and 37 model parameters and seven initial values were identified. Despite the limited monitoring data and the associated gross uncertainty, the model could simulate the reclaimed water quality in the RWDS with acceptable accuracy. Regional sensitivity analysis suggested that the model had a balanced structure with a large proportion of sensitive parameters, and the sensitivity of model parameters could be reasonably interpreted by current knowledge or observation. Furthermore, the most sensitive model parameters could generally be well identified with uncertainties significantly reduced, which also favored the trustworthiness of the model. Finally, future plans to improve and apply the model were also discussed.
- Preparation of wrapped nZVI particles and their application for the
degradation of trichloroethylene (TCE) in aqueous solution
- Authors: Wenjing Fan; Yue Cheng, Shuzhen Yu, Xiaofeng Fan Yaqian Deng
Abstract: Three types of wrappped nanoscale zero-valent iron (W-nZVI) with different coatings including agar, starch, and carboxyl methyl cellulose, were synthesized using a rheological phase reaction method. The structure and morphology of W-nZVI particles were characterized by scanning electron microscopy and transmission electron microscopy. Batch degradation experiments exhibited that W-nZVI dosage, initial trichloroethylene (TCE) concentration and solution pH had significant effects on TCE dechlorination. Experimental results proved that the highest dechlorination efficiency was obtained within 320 minutes for 10 mg/L of TCE at the optimal pH of 5.0 and W-nZVI dosage of 0.5 g/L. Kinetic study revealed that TCE dechlorination by W-nZVI in aqueous solution obeyed the quasi-first-order reaction kinetics. The product after the reaction could be easily separated by the permanent magnet for re-use.
- Water reuse perceptions of students, faculty and staff at Western
- Authors: D. Velasquez; E. K. Yanful
Abstract: Global fresh water resources are under increasing pressure from rapidly growing demands and changing climatic conditions. Wastewater reclamation is becoming an important alternative for sustainable water resources management and building climate change resiliency in many regions around the world. Public acceptance and trust of consumers in the quality of reclaimed water is considered by many to be the most important factor determining the outcomes of water reclamation projects. Knowledge of the urban water cycle and water reuse perceptions of student, faculty and staff at Western University were investigated. Results showed that members of the university community are more likely to accept reclaimed wastewater for applications that do not involve drinking or close personal contact. Knowledge of the urban water cycle and water resources in Canada is modest among the university community with a moderate (G = 0.303, p < 0.05) positive relationship between ‘water knowledge’ and ‘close contact acceptability’. The majority of the university community (75.8%) thinks that reclaiming water to provide an alternate source of water in southwestern Ontario is a good idea, but there are still concerns about the presence of chemicals such as pharmaceuticals from reclaimed water and the long-term effects on human health from exposure to these contaminants.
- Controlling biofouling of reverse osmosis membranes through surface
modification via grafting patterned polymer brushes
- Authors: Wen Ma; Md. Saifur Rahaman Heloise Therien-Aubin
Abstract: Thin film composite (TFC) polyamide membranes are extensively used as selective barriers in reverse osmosis processes. The major challenge faced with TFC membranes is significant fouling on the surface, which restricts the overall purification performance. To address the fouling problem, we developed novel fouling-resistant surface coatings via polyelectrolyte [poly(allylamine hydrochloride)/poly(styrene sulfonate)] layer-by-layer self-assembly, functionalized with patterned antimicrobial and antifouling/fouling-release polymer brushes. Two types of different polymer brushes, among antimicrobial poly(quaternary ammonium), antifouling poly(sulfobetaine) and fouling-release poly(dimethylsiloxane) (PDMS), were selected and grafted in a checkerboard pattern, with a square feature of 2 µm. The successful patterning and incorporation of different polymer brushes on the membrane was confirmed through X-ray photoelectron spectroscopy analysis. Grafting with sulfobetaine and PDMS significantly increased the hydrophilicity and lowered the surface energy of the membrane, respectively. The fouling-resistant property of the modified membrane was evaluated via static protein (bovine serum albumin) deposition and bacterial (Escherichia coli) cell adhesion tests. Surface modifications proved to diminish protein adhesion and exhibited 70–93% reduction in bacterial cell attachment. This observation suggests that the modified membranes have strong antifouling properties that inhibit the irreversible adhesion of organic and bio-foulants on the membrane surface.
- Removal of hexavalent chromium by chemical modification of
kinetic and equilibrium modeling
- Abstract: This study aimed to synthesize a new resin through immobilization of the 4,4′-((1Z,11Z)-2,5,8,11-tetraazadodeca-1,8-diene-1,11-diyl)diphenol (TRA) onto silica gel modified (Si-CPTS) with 3-chloropropyltrimethoxy silane (CPTS) and its application for the removal of chromium(VI) ions from aqueous solution as well as from industrial wastewater. The same applications were also made for industrial wastewater vapor. The objective purpose of this work was to investigate the influences of concentration, temperature, amount of metal ions, contact time and pH to sorption on the surface modified by TRA (Si-TRA). The newly synthesized Si-TRA is characterized with scanning electron microscope and elemental analysis and Cr(VI) heavy metal ions were used as sorbate. The sorption of Cr(VI) ion was evaluated by using batch methods. The value of adsorption of Cr(VI) ion was detected with an atomic absorption spectrometer. The maximum adsorption capacities and isotherm parameters were calculated from the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm equations. Thermodynamic parameters such as free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) were also calculated from the sorption results. The modified structure used as adsorbent was successfully employed in the removal of Cr(VI) ions from the samples of industrial wastewater.
- Effect of coagulant and flocculant addition scheme on the treatment of
dairy farm wastewater
- Abstract: Our group was approached by a manufacturer of treatment trains to recycle wastewater from dairy farm manure. Company X treatment trains consist of microscreening, sedimentation and filtration units attached to a reverse osmosis (RO) membrane. To enhance screening, a coagulant and a flocculant are added to the stream feeding the microscreen. However, their customers experience foaming on the microscreen as well as frequent fouling of the RO membranes. This study aimed to identify the source of foaming and to optimize the performance of the treatment train. Results show that interactions between the alum coagulant, the polymer flocculant and the contaminants are the cause of foaming. Addition of silicon polymer antifoam A effectively reduced foaming, while maintaining the same removal of total suspended solids (TSS) and total organic carbon (TOC). Alternatively, we proposed a new reagent addition scheme which circumvents back-to-back addition of the polymer flocculant and the alum coagulant. The proposed scheme resulted in significant reduction in foaming and ∼50% increase in TSS and TOC removal, even at the 40% lower dose of the cationic polymer. In addition to the economic benefit, a low concentration of left-over polymer should alleviate the fouling of the RO membrane.
- Microwave and its combined processes: an effective way for enhancing
anaerobic digestion and dewaterability of sewage sludge?
- Authors: Jibao Liu; Juan Tong, Yuansong Wei Yawei Wang
Abstract: The enhancement for sludge anaerobic digestion and dewaterability were investigated in sludge pretreated by microwave (MW) and its combined processes. The results showed that microwave and its combined processes can efficiently release soluble organic matter and thus enhance anaerobic digestion of sludge. The cumulative methane production in the test of the MW-H2O2-OH (0.2) process was increased by 13.34% compared with that of the control. The MW-H process was effective in improving sludge dewaterability, e.g., the capillary suction time (CST) at only 9.85S.
- Enhanced biodegradation of oily wastewater through nuclear irradiation
mutation and statistical experimental methodology
- Authors: Xin-Guo Duan; Yong-Ming He, Zhong-Quan Li Shuang Li
Abstract: This study presents the improved biodegradation of crude oil in aqueous phase using mutant Dietzia sp. obtained by random mutagenesis of wild Dietzia sp. using 60Co-γ irradiation. The mutants obtained were screened based on their degradation performance and the best mutant was selected for oil degradation optimization research. A four factor central composite design coupled with response surface methodology was applied to evaluate and optimize the important variables. A genetically stable mutant, designated as M22, was isolated and demonstrated significantly higher degradation efficiency (52.5%) of total petroleum hydrocarbons (TPHs) than the parental strain (28.2%) in liquid media after 14 days of incubation. Increased production of enzyme responsible for the degradation was achieved with the mutant species. Optimum conditions were determined to be pH 7.6, 0.20 g/L K2HPO4, 0.57 g/L NH4NO3, and 0.62 g/L yeast extract. Approximately 68.5% of TPH was experimentally degraded after 14 h of incubation under the optimum conditions, which agreed well with the model prediction. Gas chromatography-mass spectrum analysis showed that the mutant M22 could degrade a wide range of crude oil fractions, while optimization of culture conditions could be effective for increasing its strain's degrading ability.