S. Esplugas

Pharmaceuticals and organic pollution mitigation in reclamation osmosis brines by UV/H2O2 and ozone.

One significant disadvantage of using reverse osmosis (RO) for reclamation purposes is the need to dispose of the RO retentates. These retentates contain a high concentration of micropollutants, effluent organic matter (EfOM) and other inorganic constituents, which are recalcitrant to biological treatment and may impact the environment. The occurrence of 11 pharmaceuticals (concentrations ranging from 0.2 to 1.6 μg L(-1)) and their mitigation in RO retentates by a UV/H2O2 process and ozonation was studied using a wide range of oxidant dosages. Eleven pharmaceuticals were identified at. Initial observed kinetic constants (kobs) were calculated for the different pharmaceuticals. Other typical wastewater parameters were also monitored during the UV/H2O2 and ozonation reactions. The range for kobs was found to be 0.8-12.8L mmol O3(-1) and 9.7-29.9 L mmol H2O2(-1) for the ozonation and UV/H2O2 process, respectively. For ozonation, Atenolol, Carbamazepine, Codeine, Trimethoprim and Diclofenac showed the lowest initial kobs (in the order mentioned). Atenolol and Carbamazepine appeared as the most ozone resistant pharmaceuticals, exhibiting the lowest percentage of elimination at low ozone doses. On the other hand, despite the non-selectivity of HO, differences in the initial kobs were also observed during the UV/H2O2 process. Trimethoprim, Paroxetine and Sulfamethoxazole exhibited the lowest initial kobs values (in the order mentioned). Trimethoprim and Paroxetine also exhibited the lowest percentage removal when low H2O2 doses were assayed. The compounds that were identified as problematic during ozonation were more efficiently removed by the UV/H2O2 process. UV/H2O2 generally appeared to be a more efficient technology for removing pharmaceuticals from RO brines compared to ozonation.

Reverse osmosis concentrate treatment by chemical oxidation and moving bed biofilm processes

In the present work, four oxidation techniques were investigated (O3, O3/UV, H2O2/O3, O3/H2O2/UV) to pre-treat reverse osmosis (RO) concentrate before treatment in a moving-bed biofilm reactor (MBBR) system. Without previous oxidation, the MBBR was able to remove a small fraction of the chemical oxygen demand (COD) (5-20%) and dissolved organic carbon (DOC) (2-15%). When the concentrate was previously submitted to oxidation, DOC removal efficiencies in the MBBR increased to 40-55%. All the tested oxidation techniques improved concentrate biodegradability. The concentrate treated by the combined process (oxidation and MBBR) presented residual DOC and COD in the ranges of 6-12 and 25-41 mg L(-1), respectively. Nitrification of the RO concentrate, pre-treated by oxidation, was observed in the MBBR. Ammonium removal was comprised between 54 and 79%. The results indicate that the MBBR was effective for the treatment of the RO concentrate, previously submitted to oxidation, generating water with an improved quality.

Combination of photo-Fenton and biological SBBR processes for sulfamethoxazole remediation

A combined strategy of a photo-Fenton pretreatment followed by a Sequencing Batch Biofilm Reactor (SBBR) was evaluated for total C and N removal from a synthetic wastewater containing 200 mg L(-1) of the antibiotic Sulfamethoxazole (SMX). Photo-Fenton reaction was performed with two different H2O2 concentrations (300 and 400 mg L(-1)) and 10 mg L(-1) of Fe2+. The pre-treated effluents with the antibiotic intermediates as sole carbon source, together with a nutrients solution, were used as feed for the biological reactor. The SBBR was operated under aerobic conditions to mineralize the organic carbon and the hydraulic retention time (HRT) was optimized down to 8 hours. Then, an anoxic denitrification stage of 24 hours of HRT was added right after the aerobic stage of the same duration in order to remove the NO3(-) generated along the chemical-biological treatment. TOC, COD and SMX concentrations together with O2 uptake rate (OUR) profiles were monitored in purpose of assessing the performance of the system. NO3(-), NH4+ and total N concentrations were analyzed to find out the fate of N contained in the initial SMX molecule. A start up strategy resulted in the correct formation of a biofilm over the volcanic support. The total TOC removals achieved with the combination of the chemical and the biological processes were 75.7 and 87.7% for the low and the high H2O2 concentration pretreatments respectively. Practically all N present in the SMX solution was eliminated in the SBBR when the aerobic-anoxic strategy was used.