Investigating the efficiency and kinetic coefficients of nutrient removal in the subsurface artificial wetland of Yazd wastewater treatment plant

Background: Investigating the performance of naturally operated treatment plants may be due to the fact that they cannot be operated as desired, or that they should be modified to achieve good performance e.g. for nutrients removal. The advantage of kinetic coefficient determination is that the model can be adjusted to fit data and then used for analyzing alternatives to improve the process. This study investigates the efficiency of subsurface artificial wetland and determines its kinetic coefficients for nutrient removal

Methods: The present study investigated the kinetics of biological reactions that occurred in subsurface wetland to remove wastewater nutrient. Samples were taken from 3 locations of wetlands for 6 months. The nutrient content was determined through measuring Total Kjehldahl Nitrogen [TKN], ammonium, nitrate, and phosphate values

Results: Average levels for TKN, ammonium, nitrate, and phosphate in effluent of control wetland were 41.15, 23.59, 1.735, and 6.43 mg/L, and in wetland with reeds were 28.91, 19.99, 1.49 and 5.63 mg/L, respectively. First-order, second-order, and Stover-Kincannon models were applied and analyzed using statistical parameters obtained from the models [U[max], K[B]]

Conclusion: The nutrients removal at Yazd wastewater treatment plant was remarkable, and the presence of reeds in wetland beds was not very efficient in improving system performance. Other more efficient plants are suggested to be evaluated in the system. Stover-Kincannon kinetic model provided predictions having the closest relationship with actual data obtained from the field

Application of modified bentonite using sulfuric acid for the removal of hexavalent chromium from aqueous solutions

Background: Environmental contamination by chromium [Cr] has become an important issue due to its adverse effects on human health and environment. This study was done to evaluate the application of modified bentonite using sulfuric acid as an adsorbent in the removal of hexavalent Cr from aqueous solution

Methods: Adsorbent features were determined using x-ray diffraction [XRD], fourier transformed infrared spectroscopy [FTIR] and scanning electron microscope [SEM] techniques. Thereafter, the effect of pH, contact time, adsorbent dosage and different concentrations of Cr was investigated. The experimental data was fitness in terms of kinetic and equilibrium adsorption processes

Results: The maximum capacity [Qm] of Cr[VI] according to Langmuir model was obtained at 4.21 mg/g. The experimental data properly obeyed the Longmuir and pseudo-second-order models. The highest percentage of Cr[VI] adsorption was observed at pH = 3 and the process after 60 minutes reached the equilibrium state

Conclusion: In Langmuir expression, the dimensionless constant separation term [RL] values for the adsorption of Cr onto the modified bentonite was in the range of 0-1, indicating that the adsorption is a favorable process and the modified bentonite has good potential in removing hexavalent Cr using sulfuric acid

Performance evaluation of wastewater stabilization ponds in Yazd-Iran

Background: Yazd waste stabilization pond facilities consist of three stabilization pond systems, module 1, module 2 and module 3 that AWSP module 1 has started its operation. The existing facilities have had several problems in their operation. The objectives of this research were to evaluate the performance of stabilization ponds in wastewater treatment of the city of Yazd, due to several problems in their operation, and to prepare a scheme of its upgrading, if necessary

Methods: During the period from December to June 2010, data analysis were carried out for both raw and treated wastewater

Results: Results of these investigations showed that the average effluent concentrations of Biochemical Oxygen Demand 5 [BOD[5]], Chemical Oxygen Demand [COD] and Suspended Solid [SS] taken from anaerobic pond and secondary facultative ponds of module 1 were 306.9, 135.18, 139.75 and 136.75, 69.025, 136.5 mg/L, respectively

Conclusion: These results indicated that the effluent of the anaerobic pond of module 1 was complied with the Iranian treated wastewater standards for agricultural reuse in terms of BOD[5] and COD concentrations; hence the secondary facultative ponds could be changed to other primary facultative ponds in order to increase the capacity of wastewater treatment plant

[Evaluation of the status of citizen participation in municipal waste source separation plan and offering corrective strategies]

To implement source separation plan, awareness of viewpoints and participation of waste producers are necessary. The aim of this research is to assess the status of the source separation of municipal wastes and to offer its corrective strategies from citizens' point of view. This descriptive crooss-sectional study was performed through filling 1400 questionnaires by in-person interview in Qom, Yazd, and East Azarbaijan in the form of a waste management master plan. In this study, awareness of population was assessed using a questionnaire consisting of 31 general and specific questions. To examine the relationship between qualitative variables and cross-tabulations, chi-square test was used at a significance level of 5%. Ninety percent of citizens declared their readiness to implement the source separation of municipal wastes. Most important reasons of citizens for implementation of this plan was better recycling with appropriate quality materials [79%], environmental protection and health promotion [65%] and assistance to municipalities [43%], and the important reasons of plan's failure from citizens point of view were: lack of or irregular implementation the programs by the municipality [45%], inadequate training of citizens [32%], and poor cooperation of people due to cultural and social problems and/or lack of economic justification [25%]. According to the results, high percentage of citizens were aware of separation of municipal wastes plan and knew its advantages, so if reforms are made by the municipal authorities, percentage of participation and cooperation of citizens in this project will favorably increase

20 years view study_of dry waste recycling in Qom and it's economic benefits

Background and Objective: According to the existing documents a major portion of municipal solid wastes in Iran is being land filled and small portion of this material is recycled, while the municipal waste management in developing countries has moved towards source separation and recycling. This research was conducted by the purpose of estimating Qom municipal solid waste recycling potential and cost benefits in a 20-year vision since 2006

Materials and Methods: This Research is a cross-sectional study. Firstly, according to the reports given by waste management organization in Qom city, dry solid waste recycling in 2006 and 2011 was estimated. Then two scenarios consisted of 20 and 60 percents of recycling were estimated to process the solid waste in 2011 and 2028 for enhancing recycling level, and then cost benefit of them was determined

Results: The average of produced solid waste was 718 ton per day in Qom city in 2011. Due to this producing process in 1407 we will have 1145 ton solid waste per day in this city. Daily economic benefit of dry solid waste recycling in 2011 was 15801520 Rials. If the recycling programs promotes, this benefit can be increased to 63211640 and 189664400 Rials for 20 to 60%recycling level

Conclusion: Despite of 21 % potential for dry solid waste recycling in Qom city, nowadays about 5% of this substances are recycling. By upgrading the plan for 10 to 20 years, amount of economic benefit can be increased to 4 to 12 times