Comparative Study on Using Various Recovery Stimulation Methods to Boost Nitrification Recovery in SBRs Inhibited by Hazardous Events

A system consisting of six SBR units was operated in parallel for three phases to investigate the impacts of salinity shock and anaerobic and aerobic starvation on the activated sludge process stability and effects of various recovery stimulation methods on the subsequent recovery period. Different recovery strategies were applied in each SBR unit, including natural recovery, adding bio-accelerators, a stepwise increase feed strategy, a stepwise strategy coupled with bio-accelerators dosing, extended aeration time, and extended aeration time coupled with bio-accelerators dosing. It was concluded that the combination of stepwise strategy and dosing bio-accelerators showed the most efficiency in boosting system recovery after being subjected to NaCl shock and starvation. The boosting effect of the stepwise strategy alone was slightly better in recovery after NaCl shock. Furthermore, extending the aeration rate could bring more positive effects when resuscitating the system after long-term anaerobic starvation. For the unit that only received dosing of bio-accelerators during the recovery period, it could be concluded that there was a specific time requirement for the bio-accelerators to take effect significantly, as the impact of bio-accelerators on the beginning days of recovery periods was very slight. In contrast, adjusting operational regimes such as stepwise increased feed volume or extending aeration time could significantly boost the SBRs from the first recovery days. Hence, highly effective recovery efficiency could be achieved by coupling dosing bio-accelerators with other operational adjustment methods, especially stepwise strategies.

Experimental Investigation of a Pilot-Scale Concerning Ex-Situ Bioremediation of Petroleum Hydrocarbons Contaminated Soils

The soil samples were taken from the site of a former oil products depot from an industrial area (Romania). The soil samples taken were analyzed from a physical and chemical point of view: texture, pH, soil micronutrient content, metals concentration and petroleum hydrocarbon concentration (PHCs). The soil contaminated with total petroleum hydrocarbon (TPH (4280 mg kg−1) was disposed in the form of a pile (L × W × H: 3000 × 1400 × 500 mm). Experiments on a pilot-scale were conducted over 12 weeks at constant pH (7.5–8), temperature (22–32 °C), nutrient contents C/N/P ratio 100/10/1, soil aeration time (8 h/day) and moisture (30%). Samples were taken every two weeks for the monitoring of the TPH and the microorganisms content. During the experiment, microorganisms were added (Pseudomonas and Bacillus) every two weeks. Results of the analyses regarding the concentration of PHCs were revealed a linear decrease of the concentration of PHCs after only two weeks of treatment. This decrease in concentration was also achieved in the following weeks. Following the analysis performed on the model at the pilot scale regarding the depollution process, it can be concluded that a soil contaminated with petroleum hydrocarbons can be efficiently depolluted by performing an aeration of 8 h/day, adding microorganisms Pseudomonas and Bacillus to ensure the conditions for increasing in the total number of germs (colony forming units–CFU) from 151 × 105 to 213 × 107 CFU g−1 soil, after 12 weeks of soil treatment—the depollution efficiency achieved is 83%.

Influence Modeling and optimization of sulphide removal by catalytic oxidation of tannery fur effluents [Modelamiento y optimización de la remoción de sulfuros por oxidación catalítica de efluentes de pelambre de curtiduría]

The residual effluents from the fur stage of the bovine leather tannery industry are characterized by having a high concentration of sulfides. The objective of this study was to evaluate the effects of aeration time and pH in the residual effluents of the leather stage of the tannery, with the catalysts MnO2 and MnSO4 separately; as well as, determine adjustment models through the response surface methodology and the optimal intervals of the best conditions that lead to a higher percentage of sulfide removal. For this reason, the sulphide removal percentage was evaluated from samples extracted from the pellet stage, by means of catalytic oxidation treatments; varying the catalyst, pH and aeration time. The catalysts used were manganese dioxide (MnO2) and manganese sulfate (MnSO4) and for each catalyst the pH was varied in the values ​​of 8.5; 9.5; 10.2 and 13.4; likewise, the aeration time was varied in the values ​​of 30, 60, 90, 120, 150, 180, 210 and 240 minutes. 64 treatments were carried out, with 3 repetitions each, reporting the average values ​​of the sulfide removal percentage. The response surface methodology was used to adjust the correlation of the variables to a quadratic model; Likewise, through contour graphs the regions with the highest percentage of sulfide removal were easily identified and by superimposing contour graphs the optimal ranges of the variables pH and aeration time were determined for removal percentages greater than 98%. Based on this evaluation, it is proposed for treatments with manganese dioxide, aeration times between 160 to 240 min and pH between 8.5 to 9 and for treatments with manganese sulfate, aeration times between 110 to 240 min and pH between 8.5 to 9.8. The coefficients of multiple determination R2 for the models with catalyst MnO2 and MnSO4 were 97.51% and 95.12% respectively. With the MnSO4 catalyst, higher removal percentages were achieved at a shorter aeration time, compared to the treatments carried out with the MnO2 catalyst.

Experimental Investigation of a Pilot-Scale Concerning Ex-Situ Bioremediation of Petroleum Hydrocarbons Contaminated Soils

The soil samples were taken from the site of a former oil products depot from an industrial area (Romania). The soil samples taken were analyzed from a physical and chemical point of view: texture, ph, soil micronutrient content, metals concentration and petroleum hydrocarbon concentration (PHCs). The soil contaminated with TPH (4280 mgkg-1) was disposed in the form of a pile (LxWxH:3000x1400x500 mm). Experiments a pilot-scale were conducted over 12 weeks at constant pH (7.5–8), temperature (22–32oC), nutrient contents C/N/P ratio 100:10:1, soil aeration time (8 hour/day) and moisture (30%). Samples were taken every two weeks for the monitoring of the TPH and the microorganisms content. During experiment every two weeks were added microoganisms (Pseudomonas and Bacillus). Results of the analyzes regarding the concentration of PHCs were revelead a linear decrease of the concentration of PHCs after only two weeks of treatment. This decrease in concentration was also achieved in the following weeks. Following the analysis performed on the model at the pilot scale regarding the depollution process, it can be concluded that a soil contaminated with petroleum hydrocarbons can be efficiently depolluted by performing an aeration of 8 h/day, adding microorganisms Pseudomonas and Bacillus to ensure the conditions for increasing in the total number of germs (colony forming units–CFU) from 151x105 to 213x107 CFU/gram of soil, after 12 weeks of soil treatment - the depollution efficiency achieved is 83%.

Effect of controlling filamentous bulking sludge by Sequencing Batch Reactor Activated Sludge Process

Three groups of SBR reactors A, B and C with different aeration time were set up to culture the activated sludge which has already bulked. The results showed that the settling performance of activated sludge in reactor A changed a little, but reactors B and C had been significantly improved. High-throughput sequencing results showed that the aeration time had a significant inhibitory effect on the growth of Thothrix, and the longer the aeration time was, the more obvious the inhibition was. When the aeration time is more than 6h, the SBR mode can effectively inhibit filamentous sludge bulking, and the longer the aeration time, the better the effect.

Examination of Material Compatibilities with Ionized and Vaporized Hydrogen Peroxide Decontamination

Hydrogen peroxide (HP) decontamination is effective for a wide spectrum of pathogenic microorganisms. However, exposure to HP causes deleterious effects on some materials. The purpose of this study was to examine material compatibilities with ionized and vaporized hydrogen peroxide (iHP and VHP). With regard to iHP, 24 kinds of materials were exposed up to 100 cycles to iHP. The tested materials included plastics, metals, woods and plated or coated goods. The procedure of iHP decontamination was as following: gas time (11 min), dwell time (15 min) and aeration time (120 min). iHP decontamination caused some damage to copper, brass, chromium plate and galvanized iron immediately after exposure. Repeated iHP decontamination caused marked damage in stainless steel and urethane-, silicone- or epoxy-coating materials. Condensation of iHP decontamination posed severe damage for the material surfaces. With regard to VHP, 36 kinds of materials were exposed for up to 200 cycles to VHP decontamination. Under dry (dehumidified) conditions, VHP decontamination caused few changes on the surfaces of resin materials in dry conditions, although some resins began to develop hardening or softening. Discoloration was found in the stainless steel and changes in its coating materials. Bleaching was also observed in wooden materials. Under condensation conditions of VHP, nylon softened and butyl rubber hardened. Condensation of VHP caused material damage such as discoloration in the stainless steel, corrosion of zinc-plated steel, and air-bubbling under the color-steel sheet. The high concentrations of HP with condensation caused severe changes in metals and resins after repeated exposure. The VHP decontamination tests provided evidence that the material damage was more severe under condensation conditions than under dry conditions. Our results demonstrate the importance of condensation of HP when using it to decontaminate equipment.

Perbandingan Kemampuan Aerasi Sembur (Spray) dengan Metode Adsorpsi Menggunakan Adsorben Serbuk Kulit Buah Kakao untuk Menurunkan Kadar Besi dan Mangan Pada Air Sumur Gali

Research on the use of the spray aeration method with adsorption of cocoa rind powder to reduce iron and manganese levels in dug well water has been carried out. This study aims to make comparisons from two methods to reduce iron and manganese in dug well water. The parameters optimized in this study are the aeration time and the variation of the addition of the adsorbent mass and the adsorption time. Based on the research results, the spray aeration time for 2 hours gave the optimal percentage reduction for Fe3+ and Mn4+ metal ions, namely 98.68% and 94.22%. Meanwhile, for adsorption using cocoa pod husk powder, the optimal reduction occurred in the adsorbent mass of 0.2 grams and the adsorption time of 60 minutes for iron and manganese 96.36% and 95.15%, respectively.