Landfill site selection via integrating multi-criteria decision techniques with geographic information systems: a case study in Naqadeh, Iran.

Sanitary landfill is still the most significant and reasonable and the least expensive waste disposal method. The process of selecting a landfill site with minimal adverse effects on the environment is a complex task, in which numerous criteria need to be taken into account. In the present research, the AHP (analytical hierarchy process) and TOPSIS (technique for order of preference by similarity to ideal solution) models were used to weigh the layers and prioritize the identified regions, respectively. In the present study, the following criteria were considered: (1) environmental criteria consisting of groundwater depth and distance from rivers, streams, and wetland/dam/lake; (2) physical criteria consisting of geology, slope percentage, distance from faults, heights, soil depth, and aspect; (3) social-economic criteria including the subcriteria land uses and distance from urban centers and villages; and finally, (4) access factors with the subcriteria distance from roads and power lines. After the preparation phase, the maps corresponding to each subscale were weighed in GIS by means of AHP. To weigh the layers and evaluate the inconsistency rate of pairwise comparisons, the Expert Choice software, in which the AHP model can be run, was used. On the output map, 11 highly suitable areas for landfill were identified via the integration of layers and the identified options and were ranked using the TOPSIS technique and five secondary criteria based on experts' views. Ultimately, area no. 12 was selected as the proposed site for the landfill in Naqadeh County. The results indicated that the combination of multicriteria decision-making models including AHP and TOPSIS can be properly utilized for the purpose of locating.

Health risk assessment of heavy metal intake due to fish consumption in the Sistan region, Iran.

The heavy metal (Pb, Cd, Cr, and Ni) content of a fish species consumed by the Sistan population and its associated health risk factors were investigated. The mean concentrations of Pb, Cd, and Cr were slightly higher than the standard levels. The Ni content of fish was below the maximum guideline proposed by the US Food and Drug Administration (USFDA). The average estimated weekly intake was significantly below the provisional tolerable intake based on the FAO and WHO standards for all studied metals. The target hazard quotients (THQ) of all metals were below 1, showing an absence of health hazard for the population of Sistan. The combined target hazard quotient for the considered metals was 26.94 × 10-3. The cancer risk factor for Pb (1.57 × 10-7) was below the acceptable lifetime carcinogenic risk (10-5). The results of this study reveal an almost safe level of Pb, Cd, Cr, and Ni contents in the fish consumed by the Sistan population. Graphical abstract ᅟ.

High-rate biological denitrification in the cyclic rotating-bed biological reactor: Effect of COD/NO3(-), nitrate concentration and salinity and the phylogenetic analysis of denitrifiers.

The effects of COD/NO3(-) ratio, nitrate concentration and salinity was tested on the performance of the CRBR in denitrification with catechol as carbon source. The maximum nitrate reduction attained at COD/NO3(-) ratio of 1. The CRBR operated at optimum COD/NO3(-) ratio could completely denitrify the nitrate at inlet concentration up to 1250mg/L without nitrite accumulation. The maximum denitrification rate in the CRBR was 3.56kgNO3(-)/m(3)d with a nitrate reduction efficiency of 99% when the bioreactor was operated at inlet nitrate loading rate of 3.6kgNO3(-)/m(3)d. The denitrification performance of the CRBR was not affected significantly by NaCl concentrations up to 20g/L. 16S rRNA fragment and phylogenetic analysis identified Pseudomonas resinovorans, Stenotrophomonas maltophilia and Bacillus cereus as the most abundant denitrifiers in biomass. Accordingly, the CRBR is a high-rate bioreactor and appropriate technology for treatment of nitrate-laden industrial wastewaters containing phenolic compounds and salinity.

Enhanced biological denitrification in the cyclic rotating bed reactor with catechol as carbon source.

The performance of CRBR in denitrification with catechol carbon source is presented. The influence of inlet nitrate concentration, hydraulic retention time (HRT), media filling ratio and rotational speed of media on the performance of CRBR was investigated. The bioreactor could denitrify over 95% of the nitrate at an inlet concentration up to 1000 mg NO3(-)/L and a short HRT as low as 18 h. The optimum media filling ratio at which the maximum denitrification was achieved in the CRBR was 30% and the contribution of media at this condition was around 36%. The optimum ratio of media filling at which the maximum denitrification was 20 rpm and the contribution of rotational speed under this condition was around 17%. According to the findings, the CRBR is a high rate bioreactor and thus serves as an appropriate technology for denitrification of wastewaters containing a high concentration of nitrate and toxic organic compounds.