Extending a Consensus-based Fuzzy Ordered Weighting Average (FOWA) Model in New Water Quality Indices

In developing a specific WQI (Water Quality Index), many quality parameters are involved with different levels of importance. The impact of experts’ different opinions and viewpoints, current risks affecting their opinions, and plurality of the involved parameters double the significance of the issue. Hence, the current study tries to apply a consensus-based FOWA (Fuzzy Ordered Weighting Average) model as one of the most powerful and well-known Multi-Criteria Decision- Making (MCDM) techniques to determine the importance of the used parameters in the development of such WQIs which is shown with an example. This operator has provided the capability of modeling the risks in decision-making through applying the optimistic degree of stakeholders and their power coupled with the use of fuzzy numbers. Totally, 22 water quality parameters for drinking purposes were considered in this study. To determine the weight of each parameter, the viewpoints of 4 decision-making groups of experts were taken into account. After determining the final weights, to validate the use of each parameter in a potential WQI, consensus degrees of both the decision makers and the parameters are calculated. The highest and the lowest weight values, 0.999 and 0.073 respectively, were related to Hg and temperature. Regarding the type of consumption that was drinking, the parameters’ weights and ranks were consistent with their health impacts. Moreover, the decision makers’ highest and lowest consensus degrees were 0.9905 and 0.9669, respectively. Among the water quality parameters, temperature (with consensus degree of 0.9972) and Pb (with consensus degree of 0.9665), received the highest and lowest agreement with the decision-making group. This study indicated that the weight of parameters in determining water quality largely depends on the experts’ opinions and approaches. Moreover, using the FOWA model provides results accurate and closer- to-reality on the significance of each of the water quality parameters. Thus, using this operator can be a precise and appropriate method to determine the parameters’ weights and importance in order to develop specific WQIs for drinking, industrial, and agricultural purposes

Assessment of Groundwater Quality for Drinking Purposes Using Water Quality Index (WQI) in Shiraz, Iran (2011 to 2015)

Drinking water quality monitoring is a prerequisite for macro planning of development programs in metropolitans, improvement in health, and water resources management. Since WQIs (Water Quality Index) are known as comprehensive tools for interpretation of water quality, this study benefitted from this tool to determine the drinking water quality trends in Shiraz, Iran in a five year period from 2011 to 2015 and figure out the factors affecting its changes in this city. For this aim, annual data of 9 water quality parameters including DO, Fecal Coliforms, pH, BOD5, NO3, PO4, temperature deviation, turbidity, and TS were collected for 45 drinking water wells located in 4 zones (Dokuhak, Derak, Sabzpushan, and Chamran) to calculate the WQI. Pairwise comparison of years in terms of WQI values was analyzed statically using post-HOC analysis in Univariable repeated measure test. The results showed that the highest and the lowest water quality level both for annual and long term evaluations belonged to Derak and Chamran zones, respectively. All the studied wells in the five years were classified in "good" quality group. According to statistically analyze the highest significant change in water quality (p-value < 0.001) was found between the two years 2013 and 2015. In terminal years of the study, the increased concentration of TS and NO3 caused a partial decrease in water quality in some sources. These significant differences can be considered as a warning for the soon future. Therefore, it makes sense to accelerate the development of sewer systems and manage uncontrolled population growth in this city to prevent further water pollution. Permanent monitoring of water quality using WQIs seems to be essential to figure out a perspective of water quality trends and proper decision-making for developments in urban areas

GPU implementation of Krylov solvers for block-tridiagonal eigenvalue problems

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-32149-3_18In an eigenvalue problem defined by one or two matrices with block-tridiagonal structure, if only a few eigenpairs are required it is interesting to consider iterative methods based on Krylov subspaces, even if matrix blocks are dense. In this context, using the GPU for the associated dense linear algebra may provide high performance. We analyze this in an implementation done in the context of SLEPc, the Scalable Library for Eigenvalue Problem Computations. In the case of a generalized eigenproblem or when interior eigenvalues are computed with shift-and-invert, the main computational kernel is the solution of linear systems with a block-tridiagonal matrix. We explore possible implementations of this operation on the GPU, including a block cyclic reduction algorithm.This work was partially supported by the Spanish Ministry of Economy and Competitiveness under grant TIN2013-41049-P. Alejandro Lamas was supported by the Spanish Ministry of Education, Culture and Sport through grant FPU13-06655.Lamas Daviña, A.; Román Moltó, JE. (2016). GPU implementation of Krylov solvers for block-tridiagonal eigenvalue problems. En Parallel Processing and Applied Mathematics. Springer. 182-191. https://doi.org/10.1007%2F978-3-319-32149-3_18S182191Baghapour, B., Esfahanian, V., Torabzadeh, M., Darian, H.M.: A discontinuous Galerkin method with block cyclic reduction solver for simulating compressible flows on GPUs. Int. J. Comput. Math. 92(1), 110–131 (2014)Bientinesi, P., Igual, F.D., Kressner, D., Petschow, M., Quintana-Ortí, E.S.: Condensed forms for the symmetric eigenvalue problem on multi-threaded architectures. Concur. Comput. Pract. Exp. 23, 694–707 (2011)Haidar, A., Ltaief, H., Dongarra, J.: Toward a high performance tile divide and conquer algorithm for the dense symmetric eigenvalue problem. SIAM J. Sci. Comput. 34(6), C249–C274 (2012)Heller, D.: Some aspects of the cyclic reduction algorithm for block tridiagonal linear systems. SIAM J. Numer. Anal. 13(4), 484–496 (1976)Hernandez, V., Roman, J.E., Vidal, V.: SLEPc: a scalable and flexible toolkit for the solution of eigenvalue problems. ACM Trans. Math. Softw. 31(3), 351–362 (2005)Hirshman, S.P., Perumalla, K.S., Lynch, V.E., Sanchez, R.: BCYCLIC: a parallel block tridiagonal matrix cyclic solver. J. Comput. Phys. 229(18), 6392–6404 (2010)Minden, V., Smith, B., Knepley, M.G.: Preliminary implementation of PETSc using GPUs. In: Yuen, D.A., Wang, L., Chi, X., Johnsson, L., Ge, W., Shi, Y. (eds.) GPU Solutions to Multi-scale Problems in Science and Engineering. Lecture Notes in Earth System Sciences, pp. 131–140. Springer, Heidelberg (2013)NVIDIA: CUBLAS Library V7.0. Technical report, DU-06702-001 $$\_$$ v7.0, NVIDIA Corporation (2015)Park, A.J., Perumalla, K.S.: Efficient heterogeneous execution on large multicore and accelerator platforms: case study using a block tridiagonal solver. J. Parallel and Distrib. Comput. 73(12), 1578–1591 (2013)Reguly, I., Giles, M.: Efficient sparse matrix-vector multiplication on cache-based GPUs. In: Innovative Parallel Computing (InPar), pp. 1–12 (2012)Roman, J.E., Vasconcelos, P.B.: Harnessing GPU power from high-level libraries: eigenvalues of integral operators with SLEPc. In: International Conference on Computational Science. Procedia Computer Science, vol. 18, pp. 2591–2594. Elsevier (2013)Seal, S.K., Perumalla, K.S., Hirshman, S.P.: Revisiting parallel cyclic reduction and parallel prefix-based algorithms for block tridiagonal systems of equations. J. Parallel Distrib. Comput. 73(2), 273–280 (2013)Stewart, G.W.: A Krylov-Schur algorithm for large eigenproblems. SIAM J. Matrix Anal. Appl. 23(3), 601–614 (2001)Tomov, S., Nath, R., Dongarra, J.: Accelerating the reduction to upper Hessenberg, tridiagonal, and bidiagonal forms through hybrid GPU-based computing. Parallel Comput. 36(12), 645–654 (2010)Vomel, C., Tomov, S., Dongarra, J.: Divide and conquer on hybrid GPU-accelerated multicore systems. SIAM J. Sci. Comput. 34(2), C70–C82 (2012)Zhang, Y., Cohen, J., Owens, J.D.: Fast tridiagonal solvers on the GPU. In: Proceedings of the 15th ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming. PPopp 2010, pp. 127–136 (2010

A Computational Fluid-Dynamics Assessment of the Improved Performance of Aerodynamic Rain Gauges

The airflow surrounding any catching-type rain gauge when impacted by wind is deformed by the presence of the gauge body, resulting in the acceleration of wind above the orifice of the gauge, which deflects raindrops and snowflakes away from the collector (the wind-induced undercatch). The method of mounting a gauge with the collector at or below the level of the ground, or the use of windshields to mitigate this effect, is often not practicable. The physical shape of a gauge has a significant impact on its collection efficiency. In this study, we show that appropriate \u201caerodynamic\u201d shapes are able to reduce the deformation of the airflow, which can reduce undercatch. We have employed computational fluid-dynamic simulations to evaluate the time-averaged airflow realized around \u201caerodynamic\u201d rain gauge shapes when impacted by wind. Terms of comparison are provided by the results obtained for two standard \u201cconventional\u201d rain gauge shapes. The simulations have been run for different wind speeds and are based on a time-averaged Reynolds-Averaged Navier-Stokes model. The shape of the aerodynamic gauges is shown to have a positive impact on the time-averaged airflow patterns observed around the orifice compared to the conventional shapes. Furthermore, the turbulent air velocity fields for the aerodynamic shapes present \u201crecirculating\u201d structures, which may improve the particle-catching capabilities of the gauge collector

A Comparative Study of Photo-Degradation of Atrazine in Aquatic Environments Using UV and UV/Fe (III)-TiO2 Processes

A vast variety of pesticides are used for agricultural pests in Iran. The release of these persistent organic pollutants into water supplies leaves adverse effects on both the environment and public health. This study aimed to compare the photo-degradation of atrazine in the aquatic environment using UV and UV/Fe (III)-TiO2 processes. The effects of parameters including pH, the initial concentration of atrazine, and reaction time on the removal of atrazine in the aqueous phase using ultraviolet radiation (1020 μW/cm2) and UV/Fe (III)-TiO2 were investigated. Residual concentrations were determined using HPLC. Finally, the data were analyzed using SPSS software (version 16) and the graph was made by MATLAB software. The results demonstrated that the atrazine removal rate in both processes was significantly increased in acidic and alkaline conditions. By increasing initial atrazine concentrations, the removal rate was increased in both processes as well. Data showed that at the lower initial concentration of atrazine (0.1 and 1mg/l) the removal rate in UV/ Fe (III) - TiO2 process was more than the UV process. However, at higher concentration, both processes were almost the same and the maximum removal efficiency (99.2% at UV and 99.11% at UV /Fe (III) - TiO2) occurred at pH=11, initial Atrazine concentration of 10mg/L and the reaction time 30 min In conclusion, UV and Fe+3-TiO2/UV process was an appropriate method to reduce atrazine in contaminated water resources

Performance of Submerged Aerated Biofilters for Wastewater Treatment and Excess Biological Sludge Production

Minimizing sludge production in the treatment facility is a reasonable measure to reduce waste in sewage treatment, especially as regards excess biological sludge. In this regard, submerged aerated filters' (SAFs) have recently found increasing applications in treatment facilities. Thanks to their treatment mechanism, they have greatly contributed to reduction of waste production and, thereby, to reduced treatment costs. Biomass growths of both attached and suspended types take place in these filters. However, little attention has been paid to suspended sludge production and to its relationship with the physical properties of the filter. The design and application criterion for these filters is the organic loadings on unit of area or unit of volume of the media used in these filters. In this study, four filters with different physical properties and different specific areas were loaded with synthetic wastewater made of low-fat dry milk powder for five different hydraulic retention times to evaluate excess sludge production rates in submerged aerated filters. It was shown that increasing specific area increased SCOD removal efficiency up to a maximum level in saturated growths after which point the removal efficiency remained unchanging or decreased. The results also revealed that decreased hydraulic retention times increased sludge production rates in all the study columns and that media with higher porosity levels produced less excess sludge despite lower pollutant removal efficiency

Assessment of Groundwater Quality for Drinking Purposes Using Water Quality Index (WQI) in Shiraz, Iran (2011 to 2015)

Drinking water quality monitoring is a prerequisite for macro planning of development programs in metropolitans, improvement in health, and water resources management. Since WQIs (Water Quality Index) are known as comprehensive tools for interpretation of water quality, this study benefitted from this tool to determine the drinking water quality trends in Shiraz, Iran in a five year period from 2011 to 2015 and figure out the factors affecting its changes in this city. For this aim, annual data of 9 water quality parameters including DO, Fecal Coliforms, pH, BOD5, NO3, PO4, temperature deviation, turbidity, and TS were collected for 45 drinking water wells located in 4 zones (Dokuhak, Derak, Sabzpushan, and Chamran) to calculate the WQI. Pairwise comparison of years in terms of WQI values was analyzed statically using post-HOC analysis in Univariable repeated measure test. The results showed that the highest and the lowest water quality level both for annual and long term evaluations belonged to Derak and Chamran zones, respectively. All the studied wells in the five years were classified in "good" quality group. According to statistically analyze the highest significant change in water quality (p-value < 0.001) was found between the two years 2013 and 2015. In terminal years of the study, the increased concentration of TS and NO3 caused a partial decrease in water quality in some sources. These significant differences can be considered as a warning for the soon future. Therefore, it makes sense to accelerate the development of sewer systems and manage uncontrolled population growth in this city to prevent further water pollution. Permanent monitoring of water quality using WQIs seems to be essential to figure out a perspective of water quality trends and proper decision-making for developments in urban areas

Atrazine Removal from Aqueous Solutions using Submerged Biological Aerated Filter

Atrazine is widely used in the agriculture as an herbicide. Due to its high mobility, Atrazine leaks into the groundwaters, surface waters, and drinking water wells. Many physical and chemical methods have been suggested for removing Atrazine from aquatic environments. However, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. In this study, biodegradation of Atrazine by microbial consortium was evaluated in the aquatic environment. In order to assess the Atrazine removal from the aquatic environment, submerged biological aerated filter (SBAF) was fed with synthetic wastewater based on sucrose and Atrazine at different hydraulic retention times (HRTs). The maximum efficiencies for Atrazine and Soluble Chemical Oxygen Demand (SCOD) removal were 97.9% and 98.9%, respectively. The study findings showed that Stover-Kincannon model had very good fitness (R2 > 99%) in loading Atrazine in the biofilter and by increasing the initial concentration of Atrazine, the removal efficiency increased. Aerobic mixed biofilm culture was observed to be suitable for the treatment of Atrazine from aquatic environment. There was no significant inhibition effect on mixed aerobic microbial consortia. Atrazine degradation depended on the strength of wastewater and the amount of Atrazine in the influen