Correction to: Evaluation of iron and manganese removal effectiveness by treatment plant modules based on water pollution index; a comprehensive approach.

[This corrects the article DOI: 10.1007/s40201-021-00665-2.].

Evaluation of iron and manganese removal effectiveness by treatment plant modules based on water pollution index; a comprehensive approach.

Groundwater is a viable alternative when access to surface water resources is limited. Iron and manganese are known ions in soil and naturally in groundwater sources. However, human activities also are responsible. To identifying the best module for removing manganese and iron in the water treatment plant (WTP) of Mazandaran, 516 samples were taken from raw and treated water. The concentration of manganese, iron, was measured by atomic absorption spectrophotometry, and turbidity was used with the nephelometry method. The water pollution index (WPI) was applied for categorizing the status of pollution in treated water. The effect of seasonal temperature and backwashing (At flow rates of 3.5, 9.2, and 15.3 m h-1) on the sand filter efficiency was also investigated. The highest concentrations of manganese, iron, and turbidity in raw water were 0.744, 6.70 mg L-1, and 41.8 NTU, and in treated water were 0.67, 1.09 mg L-1, and 5.58 NTU, respectively. The mean concentration of manganese and iron in raw and treated water were 0.24 ± 0.1, 0.93 ± 0.91, 0.105 ± 0.06 and 0.18 ± 0.14 mg L-1 respectively. The WPI statuses in drinking water were excellent for manganese and iron in 95.74 and 53.88 % of the samples and very poor in 1.16 and 12.01 % of the samples, respectively, and its classification for drinking water for manganese and iron was excellent ˃ good ˃ extremely polluted ˃ polluted and the concentration of iron was more than manganese in treated water. The study of temperature's effect on sand filters showed that the removal efficiency in warm seasons was higher than in cold seasons. Also, the turbulence in the backwash with the 9.2 m h- 1 rates, is lesser than other speeds, and in this flow, after 270 s, the turbidity decreases to less than 10 NTU. Spearman correlation comparison showed that the parameters amounts after filtration decreased significantly (p ≤ 0.0001) in comparison to raw water. The results showed that module #1 that used open-aeration and chlorine as oxidations, was most effective in removing iron and manganese. In the end, the WTP couldn't diminish the parameters completely and need subsidiary units.

Electrochemical removal of diazinon insecticide in aqueous solution by Pb/ß-PbO2 anode. Effect of parameters and optimization using response surface methodology.

Diazinon is one of the most extensively used organophosphorus pesticides that is used against a variety of agricultural pests and disease vectors and is resistant to biodegradation; its release into the environment is a severe environmental concern due to their widespread use. The aim of this study was to investigate the electrochemical removal of diazinon insecticides from aqueous solutions and to optimize the process by response surface methodology (RSM). This is an experimental study that was performed on a laboratory scale and in a batch mood. scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction analyses were performed to accurately evaluate and characterize the coated electrode. The central composite design (CCD) was used to investigate the influence of pH, electrolysis time, diazinon concentration, and current density, as well as the effect of their interaction on the removal of diazinon during the electrochemical process. The results showed that by increasing electrolysis time and current density and decreasing diazinon pH and concentration, diazinon removal efficiency increased. According to the results, Na2 SO4 was selected as the supporting electrolyte with the highest degradation efficiency (97.88%) compared to the other two compounds (NaCl and NaNO3 ). The linear regression coefficient (R2 ) between experiments and different response values ​​in the model was .99. The results showed that the amount of AOS in the effluent of the three-dimensional electrochemical process was increased from 0.06 to 1.22 and the COD/TOC ratio decreased from 2.62 to 1.85, respectively; this indicates the biodegradability of the diazinon insecticide through the electrochemical system. The removal efficiency of COD and TOC in optimum condition was 85.78% and 79.86%, respectively. In general, the electrochemical process using Pb/ß-PbO2 electrode compared to other methods can be used as a suitable and reliable method for the treatment of effluents containing chemical toxins such as diazinon. PRACTITIONER POINTS: Electrochemical degradation of diazinon insecticide using Pb/ß-PbO2 anode. Effect of operating parameters on electrodegradation diazinon insecticide in electrochemical processes using Pb/ß-PbO2 anode. Biodegradability study of diazinon insecticide electrodegradation using Pb/ß-PbO2 anode. Optimization operating parameters using central composite design (CCD).