Applied Water Science (v.8, #7)

Intensification of a mixing aeration tank operation by using hydraulic partitioning by Sergey Yu. Andreyev; Nikolay E. Kurnosov; Michael I. Yahkind; Konstantin V. Lebedinskiy; Dmitriy P. Alekseev (1-6).
The process of biological wastewater treatment in a mixing aeration tank for the purpose of its intensification is studied. Two variants of intensification are considered—hydraulic partitioning of aeration volume of the mixing aeration tank and use of a vortex aerator. It is proposed a calculation method of partitioning of aeration volume of the mixing aeration tank, and it is shown that partitioning can increase its performance by 1.8 times and reduce power consumption of the aeration system. The new design of the vortex aerator is described, and it is shown that its use will significantly increase the efficiency of the tank aeration system and intensify the process of biological treatment due to the increased turbulence of the activated sludge flow. In this case, the quantity of oxygen utilization rate is $${mathcal{K}}_{ ext{u}}$$ Ku  = 0.14–0.18, the relative concentration of organic contaminants is reduced to 0.20 at oxygen deficit 10% during the first aeration hour.
Keywords: Mixing aeration tank; Wastewater; Aeration; Sludge mixture; Hydraulic aeration system; Hydraulic partitioning; Vortex aerator

Immobilization kinetics and mechanism of bovine serum albumin on diatomite clay from aqueous solutions by Mehmet Harbi Çalımlı; Özkan Demirbaş; Aysenur Aygün; Mehmet Hakkı Alma; Mehmet Salih Nas; Fatih Şen (1-12).
In this research, adsorption properties of bovine serum albumin (BSA) on diatomite clay, which is an oxide mineral, were studied as a function of BSA, sodium phosphate buffer and protein concentration and pH and the thermodynamic parameters of adsorption process were investigated. The BSA adsorption experiment onto diatomite clay indicated that the BSA solution reached the maximum adsorption value at pH 5.5. It was observed that the maximum adsorption capacity (qm) of the data obtained from the adsorption studies showed a great dependence on pH. The maximum amount of adsorption in adsorption experiments can be considered as points where the electrostatic interaction for pH is appropriate. Both structural and electrostatic interaction in regions outside of the isoelectric point may have caused a decrease in BSA absorbance. The structural influences were associated with different conformational states that while BSA molecules accept changes with pH, electrostatic effects can be observed in BSA molecules behaved like soft particles. In this case, it is not possible to explain the independence of the qm–pH curves of the amount of adsorption. The protein molecules at this point are very stable. Because this value is close to the isoelectric point of serum albumin. The surface structural change of BSA and diatomite clay was studied. For this, Fourier transform infrared spectroscopy (FTIR) spectroscopy values were compared before and after the experiment. The diatomite samples used as support material were characterized by FTIR, scanning electron microscopy, thermogravimetric analysis and Brunauer Emmett–Teller surface area analysis. The thermodynamic functions such as enthalpy, entropy, Gibbs free energy and activation energy were investigated in their experimental work. The thermodynamic parameters such as Gibbs free energy (ΔG*), E a, ΔH* and ΔS* were calculated as − 67.45, 15.41, − 12.84 kJ mol−1 and − 183.28 J mol−1 K−1 for BSA adsorption, respectively. We can deduce that the adsorption process from the data obtained from the thermodynamic parameters is spontaneous and exothermic. The adsorption of the process was investigated using Eyring and Arrhenius equations, and its adsorption kinetic found to be coherent with the pseudo-second-order model. As a result, we reached that the diatomite clay is a suitable adsorbent for the BSA. Experimental results showed that diatomite clay has the potency to be used for rapid pretreatment in the process of identifying proteins.
Keywords: Adsorption; Diatomite clay; Thermodynamic; Protein

Characterization of peroxidase enzyme and detoxification of phenols using peroxidase enzyme obtained from Zea mays L waste by S. Lakshmi; G. M. Shashidhara; G. M. Madhu; Rhea Muthappa; H. K. Vivek; M. N. Nagendra Prasad (1-7).
Phenol is one of the greatest menaces among the industrial pollutants. A treatment method which utilizes agricultural wastes in a simple manner has become the need of the hour. In this investigation, details on the extraction, optimization of parameters and study of detoxification potential of the peroxidase enzyme obtained from baby corn waste have been elaborated. The enzyme has been extracted from both corn silk and husk, and studies have been conducted on both the samples. Estimation of amount of protein and enzyme activity has shown promising results, and the conditions optimized are easily attainable at larger scales, making this work feasible for scale-up.
Keywords: Detoxification; Phenol; Zea Mays L waste; Peroxidase enzyme

The dye removal from aqueous solution using polymer composite films by Fatih Şen; Özkan Demirbaş; Mehmet Harbi Çalımlı; Ayşenur Aygün; Mehmet Hakkı Alma; Mehmet Salih Nas (1-9).
The composite consisted of clay and polymers like polyethylene (GCP) was used to remove methylene blue (MB) from the water. The most effective pH, temperature and initial dye concentration in adsorption process were found to be 9, 55 °C and 5 × 10−6 M, respectively. The results of the experiment showed that the adsorption process was compatible with the pseudo-second-order model. Activation parameters of ΔG: − 70.64 K J mol−1, ΔS: − 70.64 J mol−1 K−1, E a: 12.37 K J mol−1 at 308 °C were calculated and showed that adsorption process was exothermic and spontaneous. The results revealed that adsorption of MB on composite GCP was spontaneous and the composite of GCP f could be used for removing of MB from the water.
Keywords: Adsorption; Composite film; Polyethylene; Thermodynamic parameters

Estimation of short-duration rainfall intensity from daily rainfall values in Klang Valley, Malaysia by Abdullah Al Mamun; Md. Noor bin Salleh; Hanapi Mohamad Noor (1-10).
Data on intensity–duration–frequency or design rainfall are one of the most important information required for various hydrological and water resources studies. However, such crucial data are often unavailable in various parts of the world due to lack of enough rain gauging stations. It is not only tedious to determine design rainfall from the raw data but also occasionally impossible to calculate due to lack or absence of short-duration rainfall data. Generally, the manual rain gauges outnumber the automatic gauges, making it difficult to have adequate data on short-duration rainfall values, which is very important for urban hydrology. However, no graphical or mathematical relation could be found in the literature, which can be used for quick estimation of short-duration design rainfall from the daily rainfall data recorded by the manual stations. Annual maximum rainfall data from 143 rain gauging stations located at Klang Valley in Malaysia were used in this study. Statistical analyses and logarithmic graph fitting techniques were used to develop excellent correlation between short-duration rainfall and daily rainfall values for 96 automatic and 46 manual stations. Rainfall data analyze the design rainfall data of various duration and return periods. The 15, 30 and 45 min of short-duration rainfall, which is the most common rainfall duration in the study area, was observed to be 32.4%, 47.1% and 57.4% of the daily rainfall amount, respectively. The amount of rainfall during 1-, 2- and 3-h storm events contribute 64.9%, 76.5% and 80.9% of the daily rainfall. Such relations can be used for quick estimation of short-duration rainfall resulting in saving time, money and other resources.
Keywords: Annual maximum rainfall; Design rainfall; Global study; Short duration; Tropical climate

Water quality evaluation using water quality index and multivariate methods, Beheshtabad River, Iran by Ehsan Fathi; Rasool Zamani-Ahmadmahmoodi; Rafat Zare-Bidaki (1-6).
Rivers are critical to agriculture, industry, and the needs of humans and wildlife. This study evaluates the water quality of the Beheshtabad River in Iran’s Chaharmahal and Bakhtiari Province, using water quality index and multivariate statistical methods. Nitrate, temperature, phosphate, turbidity, dissolved oxygen, biological oxygen demand, electrical conductivity, total solids, and pH were measured at five selected stations along the river over 6 months using standard methods. Water quality index results demonstrated that water quality varied in the selected stations between average and good and that pollution in this section of the Beheshtabad River increases from upstream to downstream. Clustering and principal component analysis were also utilized. Multivariate statistical methods were used to analyze water conditions for efficient management of surface water quality. Agricultural fertilizers, upstream wastewater discharge, and fish farms constitute the main elements that decrease the water quality of the Beheshtabad River. To preserve this water resource against pollution, the implementation of stringent rules and guidelines are needed to enhance health and preserve water resources for future generations.
Keywords: Water quality index; Multivariate statistical methods; Beheshtabad River; Chaharmahal and Bakhtiari Province; Iran

In the present work, a novel biosensor (GCE/RGO/PPy/NR) based on the nanocomposite of reduced graphene oxide (RGO), polypyrrole (PPy) immobilized by nitrate reductase (NR) was developed on a glassy carbon electrode (GCE). The conductive nanocomposite (RGO/PPy) was synthesized by in situ oxidative polymerization of pyrrole in the presence of RGO in acidic medium. A facile and green path was employed to synthesize RGO from graphene oxide (GO). This was performed by a novel route using Abelmoschus esculentus vegetable extract as a stabilizing and reducing agent for GO. The composite of reduced graphene oxide and polypyrrole (RGO/PPy) was deposited onto GCE with subsequent deposition of NR enzyme on the GCE/RGO/PPy to develop GCE/RGO/PPy/NR biosensor. The surface morphology and structural features of the composites were studied by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior and electrocatalytic activity of the biosensor were examined by cyclic voltammetry at different scan rates (20–100 mV s−1) in the synthetic nitrate solution. The developed bio-anode achieved a maximum current density of 4.24 mA cm−2 at a scan rate of 100 mV s−1 for 10 mM sodium nitrate solution.
Keywords: Biosensor; Nitrate detection; Glassy carbon electrode; Nitrate reductase; Cyclic voltammetry

Multivariate statistical approaches to identify the major factors governing groundwater quality by Tao Chen; Huafei Zhang; Chengxun Sun; Hongyan Li; Yang Gao (1-6).
Multivariate statistical techniques, discriminant analysis, cluster and principal component analysis were applied to the dataset on groundwater quality of Longyan basin of Fujian Province (South China), to extract principal factors controlling the source variations in the hydrochemistry and identify the major factors affecting groundwater quality. The dataset covers ten parameters of monitored wells at five typical locations in the region. The results were evaluated in accordance with the groundwater quality standards suggested by Specification GB/T14848-93, “The Quality Standard of Underground Water.” Cluster analysis results reveal that the groundwater in the study area is classified into two groups (A: 2000–2007 and B: 2008–2011) between the sampling sites, reflecting regular characters of interannual variability. Factor analysis/principal component analysis, applied to the datasets of the two different groups obtained from cluster analysis, resulted in three factors accounting for 85.5% and 100% of the total variance in the water quality datasets, respectively. Three of the ten parameters processed by discriminant analysis obtained a conformation rate of 100% which allowed a reduction in the dimensionality of large dataset, and also it found that most discriminant parameters (total alkalinity, chloride ion, sulfate ion) are responsible for temporal variation of water quality. So this study illustrates the usefulness of multivariate statistical techniques for interpreting complex datasets of water quality, identifying pollution sources/factors for effective groundwater quality management.
Keywords: Multivariate statistics; Factor analysis; Cluster analysis; Groundwater quality

Adsorption of atrazine from aqueous solution using unmodified and modified bentonite clays by Oluwaseun Jacob Ajala; Friday Onyekwere Nwosu; Rasheed Kayode Ahmed (1-11).
Properties of raw bentonite clay of Afuze in Edo state which are abundant and cheap bentonite mineral in Nigeria as adsorbents for the removal of atrazine in aqueous solution were investigated. The bentonite clay-types were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry and X-ray diffraction (XRD). Batch adsorption experiments were carried out to determine the equilibrium characteristics, thermodynamics and kinetics of the sorption processes. The data obtained were subjected to Langmuir, Freundlich and Temkin isotherm equations, while pseudo-first-order, pseudo-second-order rate equations, intra-particle diffusion and Elovich models were considered for kinetics and mechanism. The results showed that the adsorption processes were described by different isotherm models; they were all spontaneous (∆G ranges from − 938.34 to − 6263.58 kJ/mol) and exothermic (range of ∆H is − 252.73 to − 1057.08 kJ/mol), and with decreased randomness, ∆S (− 3.110 to − 0.581 J.mol/K). Pseudo-second-order kinetics model gave the better fit for all the sorption processes which implies physisorption process as the rate limiting step. Thus, bentonite clay-types can be used to adsorb atrazine.
Keywords: Atrazine; Bentonite clay; Kinetics; Isotherm; Thermodynamics

The morphometric parameters are depicting the hydrological reaction through geographic information systems (GIS) and geospatial techniques used for water conservation. In this area, drainage system shows a dendritic pattern occasion where the most outrageous number of streams found in the primary request and the stream arrange extended by receding in stream number. The preference criteria were chosen in the pappiredipatti watershed compared to other watersheds in the sub basin based on slope condition, rainfall, and weathered zone thickness. The highest mean bifurcation ratio is 4.9 at yercaud watershed whereas the lowest mean bifurcation ration is 1.8 in kadattur watersheds. The mean bifurcation proportion was 3.125 which demonstrate that the discharge design is influenced by auxiliary aggravations. The Elongation ratio lowest in 0.53 at kadattur and highest at KRW is 0.8, form factor esteems were 0.67 and 0.1.92 which specify stretched state of the bowl having a compliment high point of the stream for longer spans. Flowing streams of the prolonged basin are less demanding to oversee for accommodating to deciding the impact of the catchment territory on hydrological valuation. In the pappiredipatti watershed was chosen preference criteria of recharge structures, number of structures 8, 12, and 30 of check dams were built on 1st, 2nd, 3rd order stream individually. Two permeation lakes were developed nearer to 3rd order stream. Artificial recharge structures in 1st order are lower than in 2nd order, according to the morphometric investigation, the 2nd and 3rd order stream are described by high penetrable, high infiltration limit and low help, which is conducive for the recharge. The accompanying observations made while settling on the sort and plan of maintainability structures for the proper location.
Keywords: Morphometric parameters; Decision support model; Bifurcation ratio; Stream orders and watershed

The biosorption process using natural materials has found widespread applications than to their inexpensiveness, availability, and reusability. The aim of this research is to investigate the efficiency of psyllium seed powder in removal of reactive orange 16 dye. The impacts of various influential parameters such as initial pH, contact time, adsorbent dose, temperature and dye concentration were evaluated using a batch biosorption method. Data analysis was conducted by SPSS 19. The removal efficiency of reactive dye 16 using the natural adsorbent psyllium was obtained to be 94% in optimal conditions (pH 4, contact time = 40 min, and adsorbent dose = 2 g/L). Biosorption equilibrium experiments indicated that the best fit was achieved with Langmuir isotherm model. Maximum adsorption capacity was found to be 206.6 mg/g at 303 K. Kinetic analysis revealed that adsorption experimental data were best fitted by pseudo-second-order model. Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. Thermodynamic evaluation indicates that a spontaneous process has occurred. Inexpensive, locally available, and effective materials could be used for dye removal in wastewater treatment processes. Undoubtedly low-cost adsorbent benefits for commercial purposes in the future.
Keywords: Psyllium; Biosorbent; Reactive dye; Isotherm; Kinetic; Thermodynamic

Cu2ZnSnS4 QDs (5–7 nm) were synthesized by chemical coprecipitation route. Using prepared Cu2ZnSnS4 QDs, a new type of BiOCl–Cu2ZnSnS4 heterostructures were prepared using bismuth nitrate as a precurssor and potassium chloride as a source of chlorine at 100 °C, 4 h. BiOCl–Cu2ZnSnS4 heterostructures were analyzed by XRD, TEM, UV–visible NIR, PL and surface area studies. The diffracted peaks of BiOCl–Cu2ZnSnS4 heterostructure show the presence of tetragonal BiOCl and did not show the intense peaks of Cu2ZnSnS4 QDs. TEM images of BiOCl–Cu2ZnSnS4 showed the deposition of Cu2ZnSnS4 QDs on the BiOCl microsphere surface. The surface area of BiOCl, Cu2ZnSnS4 and BiOCl–Cu2ZnSnS4-1 was of 1.91 m2/g, 3.06 m2/g and 13.39 m2/g, respectively. BiOCl–Cu2ZnSnS4-1 had a higher photodegradation rate for Congo red dye than BiOCl and Cu2ZnSnS4 QDs under sunlight, and that higher photoactivity was due to the heterostructure effect between BiOCl and Cu2ZnSnS4 QDs along with increased optical absorption in the visible region. Scavenger study endorses the involvement of superoxide and holes radicals in the degradation of Congo red.
Keywords: BiOCl–Cu2ZnSnS4 ; Heterostructure; Nanocomposite; Photodegradation; Congo red; Scavengers

Enyigba in south-eastern Nigeria is one of the agrarian communities facing water scarcity challenges. The open cast mining activities in the region are also compounding the water problems as a result of leakage of heavy metals that pollute the limited water resources. This study is conducted to document the current state of surface water contamination by heavy metals and its impact on domestic and agricultural uses. Thirty water samples were collected from five sources at both the upstream, middle stream and downstream of each of the selected sites. The heavy metals were analysed using the standard laboratory methods. Generally, the average concentrations of As, Cd, Cu, Pb and Zn in the studied water bodies were 17.68, 4.30, 3.14, 0.05 and 35.57 mg/l, respectively, which were above the WHO permissible limit. Contamination of water above WHO permissible limits with heavy metals in the surface waters, because of open cast mining, is considered a serious threat to both domestic and agricultural usage. The need for establishment of treatment facility, periodic monitoring of heavy metal levels, recycling plants and principal technologies to monitor the mine sites are hereby recommended.
Keywords: Acid mine drainage; Contamination; Toxic metals; Water resources

Nuisance algal growths pose a significant threat to irrigation canals for water conveyance and flood control. Copper algaecides are routinely used to control algae in moving water. In this research, we monitored an application of a new use pattern of a chelated copper algaecide to a flowing canal and evaluated efficacy using controlled bench-scale study of the field-realized exposure using an alga commonly found in flowing water (Oedogonium sp.). The highest peak copper concentration (3.17 ppm) was measured 0.80 km from the application site though it decreased significantly at each sampling interval to the 9.66 km sampling point and remained at or below 0.2 ppm at 9.66–19.31 km from the application site. Copper mass dissipated with an exponential curve (R 2 = 0.9558), and less than 10% of applied copper was recovered at or beyond 9.66 km from application. Peak concentration dissipated by exponential decay (R 2 = 0.9922) and was predicted to achieve background concentrations by 20.9 km from application. Scaled laboratory experiments showed control at exposure achieved through 6.44 km from application. This research demonstrates a method to improve operational efficiency of copper use in flowing water to achieve desired algal control, while decreasing overall copper use and complying with applicable discharge levels.
Keywords: Algae; Copper algaecide; Dissipation; Exposure; Flowing water

The anthropological activities and huge industrialization to fulfil needs of mankind are making the remarkable and disastrous effect on aquatic life and responsible for severe pollution. The research deals with the identification and detection of organic pollutants present in industrial effluent by FTIR and GC–MS techniques. The samples were collected from paint, textile and dyes industries of MIDC Thane and GIDC Ankleshwar situated in western zone of India and recognized to be the most polluted cities in Asia. The samples were collected by standard operating procedure and then operated for extraction in ether so as to dissolve maximum organic compounds. These samples after extraction sealed in airtight glass vessel and used for FTIR and GC–MS analysis. The large number of organic compounds was detected by GC–MS analysis, whereas the presence of different functional groups of organic pollutants confirmed by FTIR analysis. The physico-chemical analysis was performed for effluent samples to know the different chemical factors associated with aqua samples. The statistical analysis of collected data was carried out; it comprises the mean, standard deviation, standard errors, Pearson correlation constants and regression analysis. The calculated results compared with WHO standards and water quality index were calculated. Large number of organic and aromatic compounds identified from GC–MS data and their toxicity is discussed.
Keywords: Chemical toxicity; Effluent; Extraction; FTIR; GCMS; Physico-chemical; WQI

Sensitive analysis of ground recharge estimation model, for semiarid areas by Salah Eddine Ali Rahmani; Brahim Chibane; Abdelkader Boucefiane (1-10).
The rapid demographic evolution wields a big pressure on water resources potentialities; in addition, the climate change effects have influenced the natural renovation rate of water resources around the world. Starting from a previous published model, a sensitive analysis was established after introducing three parameters as watershed topography, stream network density and geology index to illustrate the impact of each of these parameters on the rate of groundwater recharge. This modified model has been improved by in-site experiment (soil chloride mass balance) tested in some selected sites in Sidi Slimane River located in the region of Djelfa at 300 km from Algiers (Algeria). The results obtained show that the parameters like geology, topography and the amount of rainfall and the drainage density influence the velocity of groundwater recharge. By introducing the chloride concentration in soil, the model becomes most independent and gives good results that can be used in water resources planning in semiarid land.
Keywords: Water resources potentialities; Climate change; Groundwater recharge; Chloride mass balance; Sidi Slimane River

Preparation and characterization of adsorbents derived from bentonite and kaolin clays by Friday Onyekwere Nwosu; Oluwaseun Jacob Ajala; Rukayat Motunrayo Owoyemi; Bukola Ganiyat Raheem (1-10).
The comparative study on preparation and characterization of modified bentonite and kaolin clay types is aimed at establishment of the ability of these clay types to adsorb pollutants. Its low cost, availability and recovery of clay give it added advantage of an effective adsorbent. The modified clay types were prepared by impregnation using various concentrations of either H2SO4 or NaOH in w/v ratio of 1:2. The physicochemical and adsorptive properties were investigated using standard physicochemical methods like moisture content, bulk density, pH, iodine and methylene blue numbers. FTIR, XRD and SEM analyses were also conducted on these clay types. Unmodified kaolin clay exhibited lowest moisture content (1.12%) while unmodified bentonite clay type had highest value (3.98%). The peaks at 3435 cm−1 and 3410 cm−1 assigned N–H stretching frequency were obtained for 2 M H2SO4 modified and unmodified bentonite clay types, respectively. The peaks at 912 cm−1 and 914 cm−1 that indicate the presence of Al–Al–OH deformation frequency were obtained for unmodified bentonite clay type and 2 M H2SO4 modified bentonite clay, respectively. The physical surface morphology of the clay types revealed the presence of pores with irregular shapes, while their XRD analysis showed that the clay types are crystalline. The modified clay types exhibited better potential adsorbent for removal of small metallic or gas molecules as well as large organic molecules. Adsorbents could also remove cations or anions of pollutants since their surface charge could be positive or negative depending upon pH condition.
Keywords: Bentonite clay; Kaolin clay; Adsorbent; Methylene blue number; Iodine number

Utilization of chitosan-coated superparamagnetic iron oxide nanoparticles for chromium removal by Antony V. Samrot; N. Shobana; P. Durga Sruthi; Chamarthy Sai Sahithya (1-9).
Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely used for their versatility, while it is coated with a biopolymer like chitosan that adds attraction and also increases its applications. In this study, SPION was synthesized by chemical co-precipitation method, characterized using various analytical techniques like UV–Vis, FTIR, SEM, EDX, TEM, AFM, XRD, zeta potential and Raman spectroscopy analysis. Chitosan was coated onto the SPIONs and used for water treatment to remove chromium (450 ppm concentration). Chitosan-coated SPIONs were found to remove about 80% of chromium. Freundlich model was found to be fitting better for the current study.
Keywords: Chitosan; SPIONs; Metal removal; Characterization; Chromium

Adsorption of As (III) and As (V) from aqueous solution by modified Cassia fistula (golden shower) biochar by Md. Arsh Alam; Wasim Akram Shaikh; Md. Osaid Alam; Tanushree Bhattacharya; Sukalyan Chakraborty; Bibhutibhushan Show; Indranil Saha (1-14).
The biosorption of two Arsenic (As) species [As (III) and As (V)] from aqueous solution onto activated biochar derived from Cassia fistula, belonging to Fabaceae family was studied. SEM/EDX characterization of the adsorbent showed an irregular, porous, and heterogeneous surface morphology with calcium and iron available for As binding. FTIR also showed the presence of groups responsible for As adsorption. Batch adsorption experiments were conducted to determine the optimum conditions for As adsorption to the biomass with optimum adsorbent dose, ambient temperature, initial concentration of As, pH, and stirring rate. Under optimized conditions, the maximum removal percentage was 78.1% [uptake capacity (q e) = 0.78 mg/g] for As (III) and 84.8% [uptake capacity (q e) = 0.42 mg/g] for As (V). The Freundlich isotherm model, characteristic of multilayer binding, fit the data best with R 2 values of 0.92 for As (III) and 0.96 for As (V). Fitting of the data to the Dubinin–Radushkevich model indicated physisorption, while the kinetics study suggested a pseudo-second-order reaction. Thermodynamic parameters indicated adsorption was spontaneous. In aqueous solutions, phosphate hindered As removal more than the any other ions. Regeneration studies showed a 23.0% and 21.1% recovery for arsenite and arsenate, respectively, indicating limited leaching under both acidic and alkaline conditions. The absorptive capacity of C. fistula biomass for arsenic removal was compared with a number of other reported biosorbents and was found to be considerably efficient.
Keywords: Arsenic; Biosorption; Cassia fistula ; Equilibrium; Thermodynamics; Kinetics

Antibiotics in wastewaters: a review with focus on Oman by Intisar Mohammed Al-Riyami; Mushtaque Ahmed; Ahmed Al-Busaidi; B. S. Choudri (1-10).
The occurrence of antibiotics in treated wastewater effluent has been a concern worldwide for various reasons: most importantly development of antibiotics resistance by bacteria and other microorganism, impact of antibiotics on animal life in surface water and likely consequences on humans if treated wastewater is used for drinking water supply through the process of managed aquifer recharge (MAR). Another potential area of concern is the uptake of these antibiotics by crops irrigated by treated wastewater. In Oman, wastewater treatment and reuse is pursued vigorously as a government policy. Treated wastewater is used for crop irrigation following government regulations, MAR is being contemplated and practiced in small scale and release of such waters in the ocean takes place from time to time. Some tests have been conducted on the wastewater effluent around the world to verify and detect the concentration of antibiotics in wastewater effluent. In the Sultanate of Oman, very little research has been performed on the occurrence of antibiotics in treated wastewater, removal efficiencies of treatment processes and development of antibiotics resistance. It is expected that wastewater reuse will increase substantially due to expansion of sewerage network in the capital city as well as many other cities and towns. As such, it is imperative that research be undertaken to find out various issues related to commonly used antibiotics such as ciprofloxacin, norfloxacin, erythromycin, linezolid, penicillin, ampicillin, chloramphenicol, streptomycin, minocycline, tetracycline and sulfamethoxazole in Oman and their ultimate fate through the treatment process. In addition, the development of guidelines is crucial in amounts of antibiotics acceptably occurring in treated wastewater effluent and if they could be suitable for agriculture without causing any harm. A review of the available literature and data are provided in this article. Research needs have been identified.
Keywords: Antibiotics; Occurrence; Wastewater; Treatment; Reuse; Oman

The ability of Rhizopus arrhizus biomass for the removal of dye erythrosine B from aqueous solution was explored. The dye removal capacity of the biomass was evaluated by conducting batch tests using various parameters, viz. effect of pH, biomass dosage, contact time, modified biomasses and initial dye concentrations. The adsorption process followed a pseudo-second-order kinetic model suggesting chemisorption might be the rate-limiting step. The equilibrium process was found to be in good agreement with Langmuir adsorption isotherm, and maximum adsorption capacities of 355.9 mg/g and 363.6 mg/g were achieved with both waste and acid-treated fresh biomass, respectively.
Keywords: Rhizopus arrhizus biomass; Erythrosine B; Decolorization; Kinetic models; Adsorption isotherms

Hydrochemical evaluation of Lower Niger Drainage Area, southeastern Nigeria by C. M. Okolo; B. E. B. Akudinobi; I. I. Obiadi; E. N. Onuigbo; P. N. Obasi (1-9).
Hydrochemical evaluation of parts of Lower Niger Drainage Area was studied. The distribution and concentration of the major ions were assessed. Atomic absorption spectroscopic and spectrophotometric methods were employed in the analyses of chemical species in water, and Piper, Durov and Schoeller diagrams were used in the processing and interpretation of the results. The results of the hydrochemical analysis show the generalized ionic sequence in the study area as K+ > Ca2+> Na+ > Mg2+ and Mg2+ > Ca2+ > Na+ > K+ in wet season and Cl > SO4 2− > HCO3  > NO3 in dry season, respectively. Two major water types predominate: Ca–Mg–HCO3 (17.1%) and Na–K–Cl–SO4 (82.9%). The dominant hydrochemical facies observed include Cl–SO4 and Ca–Mg–HCO3, while Cl–HCO3–NO3 occurs to a lesser degree. The various facies present depict mixing of water from different sources, weathering of carbonates and silicates and ion exchange processes leading to increased concentration of calcium and magnesium ions in relation to sodium and potassium ions. The presence of calcium, chloride and sulphate species indicates the existence of inverse ion exchange. The water in the study area shows variation in the concentration of ionic species with seasons, while the water type is not season dependent.
Keywords: Water quality; Water type; Hydrochemical analysis; Nigeria

Integrated approaches to groundwater quality assessment and hydrochemical processes in Lagos, Nigeria by Isaiah Sewanu Akoteyon; Isaac Idowu Balogun; Alabi S. Okanlawon Soneye (1-19).
Integrated approaches of water quality indices, multivariate statistical analysis, and geostatistical technique were applied to examine the groundwater quality and hydrochemical processes in Lagos, Nigeria. Fifteen samples each were randomly collected from peri-urban, rural, and urban settlements totaling 45 samples from protected dug wells during dry and wet seasons. Samples were analyzed for physicochemical parameters, anion, and cation using standard method. The result shows that 95.6% of the samples during the dry season had pH below the minimum guideline for drinking water. Factor analysis explained 73.5% and 84.2% of the variance during dry and wet seasons, respectively, and extracted two factors—salinity and weathering of minerals. Gibbs plot indicates rock-weathering process as the mechanism controlling the groundwater system. Drinking water quality index shows excellent quality. Revelle index indicates that 6.6% of the samples are strongly affected by salinity during the wet season. One-quarter of sample indicate very severe corrosion based on the water stability index in both seasons. The Piper’s plot delineated four facies with primary hardness and mixed waters being the dominant during the dry and wet seasons, respectively. The study concludes that the groundwater is suitable for drinking. The study contributes to knowledge in the mapping of groundwater salinization and water stability indices and delineation of water types for information dissemination with a view to ensuring effective groundwater quality management. A policy that will ensure adequate protection of groundwater pollution from leachates, salinity, and anthropogenic impacts was recommended for sustainable groundwater use in the region.
Keywords: Groundwater quality; Hydrochemical processes; Integrated approach; Lagos—Nigeria

In the present days, remote sensing and geographic information system (GIS) techniques are comprehensive tools for the assessment of water resource, its management and conservation. In this study, remote sensing and GIS techniques are taken into consideration for zonation of different groundwater prospects of Pravara basin. Several contributing factors in which groundwater potential of an area entirely or partially depends such as lithology, geomorphology, slope, soil, lineament density, drainage density, land use and rainfall are assessed individually as well as together for making the different groundwater prospect maps through influencing factor (IF) and frequency ratio (FR) techniques. In ArcGIS software, all these thematic layers are prepared using different satellite imageries and conventional data sets, obtained from different sources. All these layers are transformed into high-resolution raster format and meshed together in GIS environment using IF and FR methods. Groundwater prospect maps are constructed as a result of overlay analysis. Based on the constructed map of groundwater prospect zones, as a result of this study, the study area is divided into five categories of different groundwater potential zones: very high, high, moderate, low and very low. Validation of the resultant maps has shown that frequency ratio technique is having higher accuracy (AUC = 73%) compared to the influencing factors (AUC = 69%). The present study of groundwater zonation provides a simple and less time-consuming technique; also, the results can directly be used for planning and sustainable management in Pravara basin.
Keywords: Groundwater potential; Lineament; GIS; Sustainable management; IF technique; Pravara

Use of geophysical logs in hydrogeological studies and borehole designs: case study of Apapa coastal area, Lagos, Nigeria by R. A. Jimoh; O. M. Bankole; K. Ahmed; O. A. Christopher; M. A. Adeniji; J. Ebhodaghe; S. O. Sedara; P. W. Obende; O. Alebu; E. A. Ezima (1-11).
The hydrogeological study of Apapa, a coastal part of Lagos, Nigeria, has been investigated using combined geophysical borehole logs, consisting of natural gamma and electrical resistivity components and ditch cutting samples. This study utilized data from 10 boreholes to delineate freshwater aquifer and proposes the best borehole design and construction for optimum groundwater developments in the study area. The electrical resistivity log data show that the depth to the freshwater interface varies across the study area occurring between 150 and 160 m and as shallow as 110 m in a borehole. The variations in depth of the freshwater interfaces are attributed to the extent of saline/brackish water contamination and distribution of rock types. Based on these differences and the inability to identify water quality from ditch cuttings, borehole geophysical logging is a vital tool in providing in situ subsurface information of the rock types and fluid contents in groundwater studies. This further demonstrates that geophysical borehole logs play an important part in borehole design for development of water wells.
Keywords: Geophysical borehole logs; Electrical resistivity; Natural Gamma; Groundwater; Coastal aquifer; Freshwater–saltwater intrusion