Peroxymonosulfate/Solar process for urban wastewater purification at a pilot plant scale: A techno-economic assessment.

The safe reuse of reclaimed water for agricultural irrigation has been considered as an alternative, feasible and sustainable option to address water scarcity. This work aims to validate the capability of the solar water photochemical process based on the synergistic effect between peroxymonosulfate (PMS) and natural solar radiation for actual urban wastewater (UWW) purification at a pilot plant scale using a solar Compound Parabolic Collector photo-reactor. The PMS/Solar process performance was assessed by monitoring simultaneously the inactivation of naturally occurring bacteria (Escherichia coli, Total coliforms, Enterococcus spp. and Pseudomonas spp.) as a potential tertiary treatment to fit the minimum bacterial requirements for UWW purification but also additional challenges have been in deep analysed simultaneously. In this regard, a global analysis including the degradation of three Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP), the removal of antibiotic resistant elements, the residual toxicity and the treatment cost has been analysed. Different PMS concentrations (0-1 mM) were tested and an enhancement in the process performance was obtained with increasing oxidant load, obtaining the best results with 1 mM of PMS, at which detection limit (DL) of 2 CFU/mL was reached for all microbial targets after 15 min (1.1 kJ/L of accumulated solar UV-A radiation (QUV)) and 80 % of CECs removal was reached after 27 min (2.0 kJ/L of QUV) of solar treatment time. Inactivation of naturally occurring antibiotic resistant bacteria (ARB) and removal of 16S rRNA and selected antibiotic resistance genes (ARGs) (i.e., intI1, sul1, qnrS, blaTEM, blaCTX-M32, tetM) were also investigated. ARB was successfully inactivated to values below the DL, but the process was not able to completely remove ARGs. A total reduction of intI1 (30 %), 16S rRNA (19 %), sul1 (14 %), blaCTX-M32 (12 %), qnrS (10 %), blaTEM (8 %), and tetM (7 %), was obtained after 120 min (11.5 kJ/L of QUV). An absence of an eco and phytotoxic effect of treated samples was observed towards Aliivibrio fischeri and three seeds, respectively. Finally, an estimated treatment cost of 0.96 €/m3 for the simultaneous UWW disinfection and decontamination demonstrates the promising capability of this solar treatment for UWW reclamation and reuse in agriculture, especially in areas with a high solar radiation incidence.

Natural solar activation of modified zinc oxides with rare earth elements (Ce, Yb) and Fe for the simultaneous disinfection and decontamination of urban wastewater.

This study investigates the capability of modified zinc oxides (ZnO) with Ce, Yb and Fe towards the simultaneous inactivation of pathogenic bacteria (Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa) and Contaminants of Emerging Concern (CECs, Diclofenac, Sulfamethoxazole and Trimethoprim) under natural sunlight. Several catalyst loads (from 0 to 500 mg/L) were assessed as proof-of principle in isotonic solution followed by the evaluation of organic matter effect in simulated and actual urban wastewater (UWW), using bare TiO2-P25 as reference. The order of photocatalysts efficiency for both bacterial and CECs removal was: ZnO-Ce â‰… TiO2-P25 > ZnO-Yb > ZnO-Fe > photolysis > darkness in all water matrices. The best photocatalytic performance for water disinfection and decontamination was obtained with 500 mg/L of ZnO-Ce: 80% of ∑CECs removal after 45 min (4.4 kJ/L of accumulated solar UV-A energy (QUV)) and the total inactivation of bacteria (Detection Limit of 2 CFU/mL) after 120 min (14 kJ/L of QUV) in UWW. The microbial and CECs abatement mechanism was described based on the generation of hydroxyl radicals, which was experimentally demonstrated for ZnO-Ce. Additionally, no significant release of Zn2+ and Ce was detected after the solar exposure. These results point out for the first time the capability of ZnO-Ce for the simultaneous UWW disinfection and decontamination under natural sunlight.

UV-C Peroxymonosulfate Activation for Wastewater Regeneration: Simultaneous Inactivation of Pathogens and Degradation of Contaminants of Emerging Concern.

This study explores the capability of Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) for the simultaneous disinfection and decontamination of urban wastewater. Sulfate and hydroxyl radicals in solution were generated activating peroxymonosulfate (PMS) under UV-C irradiation at pilot plant scale. The efficiency of the process was assessed toward the removal of three CECs (Trimethoprim (TMP), Sulfamethoxazole (SMX), and Diclofenac (DCF)) and three bacteria (Escherichia coli, Enterococcus spp., and Pseudomonas spp.) in actual urban wastewater (UWW), obtaining the optimal value of PMS at 0.5 mmol/L. Under such experimental conditions, bacterial concentration ≤ 10 CFU/100 mL was reached after 15 min of UV-C treatment (0.03 kJ/L of accumulative UV-C radiation) for natural occurring bacteria, no bacterial regrowth was observed after 24 and 48 h, and 80% removal of total CECs was achieved after 12 min (0.03 kJ/L), with a release of sulfate ions far from the limit established in wastewater discharge. Moreover, the inactivation of Ampicillin (AMP), Ciprofloxacin (CPX), and Trimethoprim (TMP) antibiotic-resistant bacteria (ARB) and reduction of target genes (ARGs) were successfully achieved. Finally, a harmful effect toward the receiving aquatic environment was not observed according to Aliivibrio fischeri toxicity tests, while a slightly toxic effect toward plant growth (phytotoxicity tests) was detected. As a conclusion, a cost analysis demonstrated that the process could be feasible and a promising alternative to successfully address wastewater reuse challenges.

Direct oxidation of peroxymonosulfate under natural solar radiation: Accelerating the simultaneous removal of organic contaminants and pathogens from water.

This study investigates the effectiveness of non-activated peroxymonosulfate (PMS) as oxidative agent for water purification in the presence and absence of natural solar radiation. The inactivation of three pathogens (Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa) and degradation of three Contaminants of Emerging Concern (CECs) (Trimethoprim-TMP, Sulfamethoxazole-SMX and Diclofenac-DCF) was simultaneously assessed in isotonic water (IW) by testing a wide range of PMS concentrations (from 0.0001 to 0.01 mM). A significant oxidative effect of PMS in darkness was obtained for both bacteria and CEC abatement, but when irradiated with solar light, results demonstrated a great enhancement on all bacterial kinetic rates, reaching >5 Log reduction in 30 min (1.5 kJL-1 of QUV) with 0.005 mM of oxidant as the best concentration. For CECs, higher degradation performance was obtained with 0.01 mM, 80% removal of DCF, SMX and TMP was achieved in 16 min (1.5 kJL-1), 27 min (9.4 kJL-1) and 150 min (16.8 kJL-1), respectively. Besides, the influence of inorganic species on the global PMS/solar system performance was assessed by testing its effectiveness in distilled water (DW), natural well water (WeW) and diluted well water (d-WeW) at 0.01 mM. Results revealed that (i) high chloride concentration (IW) has an important positive effect, (ii) the presence of a complex inorganic chemical water composition reduced the system efficiency (WeW), and (iii) no differences were obtained from the presence of low or high contents of carbonates/bicarbonates (WeW versus d-WeW), obtaining the following global PMS/solar efficiency performance order: IW > DW > WeW = d-WeW.