Autotrophic denitrification of synthetic nitrate-contaminated groundwater in up-flow fixed-bed bioreactor by pumice as porous media

Background: Background: Increasing nitrate concentrations in groundwater resources is considered a common environmental and public health problem worldwide. In this research, an autotrophic up-flow bioreactor with pumice as media was used to study the effects of the sulfur-to-nitrogen (S/N) ratio and empty bed contact time (EBCT) on nitrate removal efficiency and byproducts. Methods: Experiments were carried out in a 3.47 L up-flow, fixed-bed reactor with 3 sampling ports. To evaluate the overall impact of S/N ratio and EBCT on the performance of the bioreactor, several phases with different S/N ratios and EBCTs were applied. Results: At a constant S/N ratio of 3.85 g/g, as EBCT decreased from 24 hours to 2 hours, the nitrate removal efficiency decreased from 98% to 64%. On the other hand, at the desired EBCT of 4 hr, as S/N ratio decreased from 3.85 to 1.51 g/g, nitrate removal efficiency was reduced from 85% to 32%. Changing the EBCT and S/N ratio also affected the effluent nitrite and sulfate concentrations as byproducts. At the S/N ratio of 3.85 g/g and EBCT of 24 hours, effluent nitrite and sulfate concentrations were 0.1 mg NO2--N/L and 463 mg SO4 2-/L, respectively. Decreasing the S/N ratio to 1.51 g/g and the EBCT to 4 hours caused drastic changes in effluent nitrite and sulfate concentrations. Conclusion: The results indicated that the autotrophic denitrification with thiosulfate as electron donor and pumice as media was feasible and applicable for nitrate contaminated groundwater

An investigation of agricultural use potential of dewatered sewage sludge

Background: One of the useful applications of Dewatered sludge (DWS) of municipal wastewater treatment plants (WWTPs) is its use as manure in agriculture; therefore, its quality characteristics should be specified. The aim of this research was to determine biological and physicochemical characteristics of DWS of Sari WWTP and compare them with standards, and also to investigate its potential use in agriculture. Methods: Sludge samples were taken from the sewage sludge of Sari WWTP. Sampling and analysis of samples parameters including fecal coliform, salmonella, helminth ova, carbon, nitrogen, C/N, phosphorus, organic matter, potassium, moisture, electrical conductivity, and PH, were performed during four seasons with three replications based on the standard method. Results: The fecal coliform, salmonella, and helminth ova of the DWS were 2.37×106 ± 1.06×106 MPN/1 g d.s weight, 47±12.92 MPN/4 g d.s weight, and 466±61.85 number/4 g d.s weight, respectively, therefore, the DWS of Sari WWTP was categorized in the class B of the EPA standard. The amounts of C/N, organic matter, carbon, nitrogen, phosphorus, potassium, moisture, electrical conductivity, and PH were obtained to be 12.7±1.15, 42.4±3.27%, 24.6±1.89%, 1.94±0.13%, 2.35±0.6%, 0.57±0.13%, 82±3.12%, 1.34±0.21 ds/m, and 7.41± 0.45, respectively. Conclusion: The DWS of Sari WWTP has a good fertility value but it cannot be safely used in agriculture and should be improved for class A by the Processes to Further Reduce Pathogens (PFRP), especially by composting. Keywords: Sewage sludge, Agricultural use, Fertilizer, Pollution control, Dewatered sludg

Baffle and fixed media effects on coliform removal and bacterial die-off rate coefficient in waste stabilization ponds (a case study in Ahvaz)

Background: The use of waste stabilization ponds is one of the cheapest wastewater treatment processes. This study evaluated the effects of baffles and fixed media on coliform removal in facultative lagoons. Methods: In this study, the settled wastewater from four pond systems of the city of Ahvaz was used as input. Each system was composed of two ponds that were connected to each other serially. Three of them were equipped with two, three, and four baffles. Packages of fixed media were installed in the first baffled pond equal to the number of baffles. During a 12-month sampling period from March 2016 to February 2017, the capability of each system to remove coliform with different detention times was studied. Results: The control system with no baffle and no media reduced the coliform index by an average of 67% in a detention time of 6 to 12 days. Increasing the baffles and fixed media in the ponds improved the coliform removal efficiency; systems with two, three, and four baffles achieved coliform removal in the amounts of 77%, 81%, and 83%, respectively. The coliform die-off coefficients (Kb) were higher in the attached growth systems than in the control system. The coefficients were determined to be 0.21, 0.26, 0.29, and 0.31 d-1 for the second ponds of the control, two-, three-, and four-baffle systems, respectively. Conclusion: This method can be used to upgrade the existing waste stabilization pond and to design new ponds with at least two baffles in the facultative lagoons

Using polymer coated nanoparticles for adsorption of micropollutants from water

© 2017 Elsevier B.V. In this study, polyvinylpyrrolidone (PVP)-coated magnetite nanoparticles were synthesized to adsorb six emerging contaminants (Tonalide, Bisphenol-A, Triclosan, Metolachlor, Ketoprofen and Estriol) from aqueous solutions. The PVP-coated NPs were characterized by dynamic light scattering (DLS) measurements, thermal analysis, and X-ray diffraction. Results indicated that PVP-coated NPs were successfully used as a separable adsorbent for removing the micropollutants from water. Adsorption results were modeled using Langmuir and Freundlich isotherms, which showed a better fit of data to the Langmuir model. The adsorbent showed good adsorption performance in which Bisphenol-A and Ketoprofen were the most effectively removed micropollutants, with 98 and 95% removal using only 0.1 mg of the adsorbent within 15 min of contact time, respectively. Kinetic studies were performed using the pseudo-second-order model to compare the performance of PVP-coated NPs with granular activated carbon (GAC) revealing the superiority of PVP-coated NPs over GAC. Thermodynamic parameters of the adsorption of the micropollutants onto the adsorbate showed the adsorption process was endothermic and spontaneous. Adsorbate regeneration studies were performed with methanol, ethanol, and the UV/H2O2 process in five regeneration cycles. Methanol treatment ensured the highest level of regeneration

Activation of Persulfate Using an Industrial Iron-Rich Sludge as an Efficient Nanocatalyst for Landfill Leachate Treatment

In this research, the performance of nanomaterials obtained from the converter sludge (CS) of Esfahan Steel Company, Iran was investigated for the activation of persulfate (PS). The experiments were conducted on real and synthetic leachates. CS showed high catalytic activity for removal of chemical oxygen demand COD and NH3 because of its high iron oxide content. The effects of pH, CS dosage, and PS/COD ratio, temperature, and reaction time on the removal of COD and NH3 were evaluated to optimize operational conditions (pH 2, CS dosage: 1.2 g L−1, PS/COD: 4, and reaction time: 60 min). Maximum COD and NH3 removal efficiencies were 73.56 and 63.87%, respectively. Finally, the optimized process was applied for treatment of a real leachate sample. Although the treated leachate was not suitable to discharge into the environment, an increase in the 5-day biochemical oxygen demand (BOD5) and biodegradability (BOD5/COD) of leachate after treatment indicated that the effluent can be biologically treated. As a consequence, it can be combined with sewage or can be returned to the landfill

Improvement of anaerobic digestion of sewage mixed sludge using free nitrous acid and Fenton pre-treatment

Abstract Background Recently, it has been indicated that free nitrous acid (FNA) and Fenton pre-treatment of waste activated sludge can enhance methane production in anaerobic digestion of waste activated sludge. In addition, it has been revealed that the substances used in these pre-treatments are both eco-friendly and economically attractive because not only are they produced in anaerobic digestion, but they are also low priced. Since primary sludge and waste activated sludge are mixed prior to anaerobic digestion in the majority of wastewater treatment plants, this study aims to assess the influence of combined FNA and Fenton on the anaerobic digestion of mixed sludge. Results According to this study’s results, methane generation from anaerobic digestion of mixed sludge was enhanced when using FNA and Fenton pre-treatment, affirming the effectiveness of the individual and combined pre-treatments in anaerobic digestion of mixed sludge. The enhanced methane production was significant in combined pre-treatments (up to 72%), compared with FNA and Fenton pre-treatment alone (25% and 27%, respectively). This corroborates the positive synergistic effect of the combined pre-treatments on methane production. The enhanced methane can be attributed to augmented soluble fractions of organic matter in addition to increased readily biodegradable organic matter, caused by the pre-treatments. Additionally, the amount of chemical oxygen demand (COD) was assessed during anaerobic digestion, and it was revealed that COD decreased considerably when the pre-treatment strategies were combined. Conclusions This study reveals that the pre-treatments are potentially applicable to full-scale wastewater treatment plants because a mixture of primary sludge and waste activated sludge was used for the pre-treatments. Additionally, combined FNA and Fenton pre-treatments prove more effective in enhancing methane production and organic removal than these pre-treatments alone. The enhanced methane production is important for two reasons: a higher amount of renewable energy could be generated from the enhanced methane production and the COD of digested sludge reduces in such a way that facilitates application of the sludge to agricultural lands and reduces sludge transport costs