The investigation of biological removal of nitrogen and phosphorous from domestic wastewater by inserting anaerobic/anoxic holding tank in the return sludge line of MLE-OSA modified system.

In this study, the biological removal of nitrogen and phosphorous (BNR) was investigated by applying modified MLE-OSA technique. To conduct this study, three pilot plants scale were designed and established: 1) MLE similar to the current method used in Sari Wastewater Treatment Plant as control reactor 2) MLE-OSA4 with 4-h hydrolic retention time in sludge holding tank 3) MLE-OSA6 with 6-h hydrolic retention time in sludge holding tank. In this modified process for combining OSA technique with MLE system, two anaerobic/anoxic tanks were installed in the return sludge line with capacities of 70 and 107 l for MLE-OSA4 and MLE-OSA6, respectively. To set up the process, outlet sewage of the primary settlement tank of Sari Wastewater Treatment Plant was used. After a period of 45-60 days and reaching the steady state, the reactors were operated and the main, controllable parameters and laboratory experiments such as DO, ORP, Temperature, pH, COD, BOD5, MLSS, and nutrients (N&P) were precisely analyzed according to standard methods for examination of water and wastewater. The results showed that utilizing MLE-OSA system with 4 and 6 h hydraulic retention times decreased the ORP by around 109 ± 9 to 160 ± 25 mv and increased sludge retention time from 29 to 33 days. Moreover the percentages of phosphorus removal efficiency in MLE, MLE-OSA4 and MLE-OSA6 processes were 31 ± 5.2, 36.8 ± 1.9, and 39.4 ± 1.9 and the percentages of total nitrogen removal efficiency were 67.2 ± 7.6, 75.6 ± 4.8, and 78.5 ± 2.2 respectively. This study revealed that the modified MLE-OSA is more efficient than MLE for P and N removal. Hence it can replace this process.

Preparation and characterization of chitosan/Fe2O3 nano composite for the adsorption of thorium (IV) ion from aqueous solution.

In this study, novel chitosan/Fe2O3nano composite Ch/Fe-Onc was synthesized and evaluated as an adsorbent for removing thorium (IV) (Th4+) ion from aqueous solution. The Ch/Fe-Onc was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Response surface methodology (RSM) was used in the optimization of Th4+ adsorption for parameters such as pH, the initial metal ion concentration (Th4+ concentration) and contact time. The statistical measures (i.e. analysis of variance, R2, the lack of fit test and the P value) specify that the developed model is proper. Furthermore, the adsorption kinetics was well defined by the pseudo-second-order equation, while the adsorption isotherms were better fitted by the Langmuir model. The adsorption capacity of Ch/Fe-Onc was 430 mg Th4+g-1 composite which leads to 99% removal at 25 °C. Moreover, thermodynamic parameters which state the natural and endothermic nature of the reactions were determined. The loaded Th4+ can be easily regenerated with HNO3 and the Ch/Fe-Onc can be used repeatedly without any significant reduction in its adsorption capacity. The desorption level of Th4+ from the Ch/Fe-Onc by using 0.1 M HNO3, was more than 95%.

An investigation of desalination by nanofiltration, reverse osmosis and integrated (hybrid NF/RO) membranes employed in brackish water treatment.

BACKGROUND: As an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran. METHODS: This study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl-1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied. RESULTS: Results showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91. CONCLUSIONS: Comparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process. The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na.

Evaluating the metallic pollution of riverine water and sediments: a case study of Aras River.

Metallic pollution caused by elements Zn, Cu, Fe, Pb, Ni, Cd, and Hg in water and sediments of Aras River within a specific area in Ardabil province of Iran is considered. Water and sediment samples were collected seasonally and once respectively from the five selected stations. Regarding WHO published permissible values, only Ni concentration in spring and summer water samples has exceeded the acceptable limit up to four times greater than the limit. The concentration of metals Ni, Pb, and Fe in river water shows a direct relationship with river water discharge and the amount of precipitation. Enhanced soil erosion, bed load dissolution, and runoffs may play a key role in remarkable augmentation of metallic ions concentration. Furthermore, excessive use of pesticides which contain a variety of metallic ions (mainly Cu) in spring and summer may also result in an increase in the metals' concentration. The potential risk of Ni exposure to the water environment of the study area is assigned to juice, dairy products, edible oil, and sugar cane factories as well as soybean crop lands which are located within the sub-basin of Aras River in the study area. Regarding the sediment samples, the bioavailable metal concentrations indicate an ascending order from the first station towards the last one. In comparison with earth crust, sedimental and igneous rocks the reported metallic concentration values, except for Cd, lie within the low-risk status. Regarding Cd, the reported values in some stations (S2, S4, and S5) are up to ten times greater than that of shale which may be considered as a remarkable risk potential. The industrial and municipal wastewater generated by Parsabad moqan industrial complex and residential areas, in addition to the discharges of animal husbandry centers, may be addressed as the key factors in the sharp increase of metallic pollution potential in stations 4 and 5.

Evolution of a new surface water quality index for Karoon catchment in Iran.

Water quality standards are developed worldwide by national and international agencies for pollution control decision-making. Use-based water quality classification criteria and Water Quality Indices (WQIs) also play an important role in the assessment of the suitability of water resources for various applications. The present study proposes a better overall index for water quality in Iran and its application in Karoon River by exploring the behavior and limitations of conventional methods for quality evaluation. For this purpose, six variables were employed. Water quality determinants of the new index include Dissolved Oxygen, Total Dissolved Solids, Turbidity, Nitrate, Fecal coliform and pH. Besides, the mathematical equations applied to transform the actual concentration values into quality indices have been formulated. This study compares a new index called the Iranian Water Quality Index with other pre-existing indices such as NSFWQI, Oregon, CPCB WQI, MDOE WQI, Kaurish and Younos WQI, and Ahmed Said WQI. Results revealed that the overall quality of the surface water falls under the 'good' class. A case study of Karoon River is made to illustrate the application of this new index system.