RESUMEN
An integrated lab-scale wastewater treatment system consisting of an anaerobic Moving Bed Biofilm Reactor (AnMBBR) and an aerobic Membrane Bioreactor (AeMBR) in series was used to study the removal and fate of pharmaceuticals during wastewater treatment. Continuous-flow experiments were conducted applying different temperatures to the AnMBBR (Phase A: 35 °C; Phase B: 20 °C), while batch experiments were performed for calculating sorption and biotransformation kinetics. The total removal of major pollutants and target pharmaceuticals was not affected by the temperature of the AnMBBR. In Phase A, the average removal of dissolved chemical oxygen demand (COD), biological oxygen demand (BOD), and ammonium nitrogen (NH4-N) was 86%, 91% and 96% while in Phase B, 91%, 96% and 96%, respectively. Removal efficiencies ranging between 65% and 100% were observed for metronidazole (MTZ), trimethoprim (TMP), sulfamethoxazole (SMX), and valsartan (VAL), while slight (<30%) or no removal was observed for carbamazepine (CBZ) and diclofenac (DCF), respectively. Application of a mass balance model showed that the predominant mechanism for the removal of pharmaceuticals was biotransformation, while the role of sorption was of minor importance. The AeMBR was critical for VAL, SMX and TMP biodegradation; the elimination of MTZ was strongly enhanced by the AnMBBR. In both bioreactors, Bacteroidetes was the dominant phylum in both bioreactors over time. In the AnMBBR, Cloacibacterium and Bacteroides had a higher abundance in the biocarriers compared to the suspended biomass.
Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Biopelículas , Anaerobiosis , Reactores Biológicos/microbiología , Sulfametoxazol , Trimetoprim , Eliminación de Residuos Líquidos , Aguas del AlcantarilladoRESUMEN
In the current study, treatment of undiluted real bilge water (BW) and the production of methane was examined for the first time using a membraneless single chamber Microbial Electrolysis Cell (MEC) with Anaerobic Granular Sludge (AGS) for its biodegradation. Initially, Anaerobic Toxicity Assays (ATAs) were used to evaluate the effect of undiluted real BW on the methanogenic activity of AGS. According to the results, BW shown higher impact to acetoclastics compared to hydrogenotrophic methanogens which proved to be more tolerant. However, dilution of BW caused lower inhibition allowing BW biodegradation. Maximum methane production (142.2 ± 4.8 mL) was observed at 50% of BW. Operation of MEC coupled with AGS, seemed to be very promising technology for BW treatment. During 80 days of operation in increasing levels of BW, R2 (1 V) reactor resulted in better performance than AGS alone. Exposure of AGS to gradual increase of BW content revealed that CH4 production was possible and reached 51% in five days even after feeding with 90% of BW using simple commercial iron electrodes. Successful chemical oxygen demand (sCOD) removal (up to 70%) was observed after gradual biomass acclimatization. Among the different monitored volatile fatty acids (VFAs), acetic and valeric acids were the most frequently detected compounds with concentrations up to 2.79 and 1.81 g L-1, respectively. The recalcitrant nature of BW did not allow the MEC-AD (anaerobic digester) to balance the consumed energy. Microbial profile analysis confirmed the existence of several methanogenic microorganisms of which Desulfovibrio and Methanobacterium presented significantly higher abundance in the cathodes compared to anodes and AGS.
Asunto(s)
Aguas del Alcantarillado , Purificación del Agua , Anaerobiosis , Reactores Biológicos , Electrólisis , Metano , Aguas del Alcantarillado/microbiologíaRESUMEN
Two free water surface (FWS) and two subsurface flow (SSF) pilot-size wetlands were constructed for the evaluation of their performance in treating highway runoff (HRO) in the heart of the Mediterranean region, the island of Crete, at the southernmost point of Greece. Detailed recordings of the resources involved during the construction allowed a thorough calculation of the cost of the systems and the requirements in materials, man-hours, and equipment. The two identical FWS systems had a surface area of 33 m(2) each, while the two identical SSF covered 32 m(2) each. One FWS and one SSF, named FWS12 and SSF12, respectively, were designed with a hydraulic retention time (HRT) of 12 h, with each one capable of treating a maximum HRO of 12.6 m(3)/day. The other couple, named FWS24 and SSF24, respectively, was designed with an HRT of 24 h, with each receiving a maximum HRO of 6.3 m(3)/days. An influent storage tank was required to hold the runoff during the common storm events and control the flow rate (and the hydraulic retention time) into the wetlands. This construction represented 25% of the total construction cost, while 5% was spent on the influent automated (and sun-powered) control and distribution system, from the storage tank to the wetlands. The respective total cost allocated to the two SSF systems (euro 14,676) was approximately 10% higher than that of the FWS (euro 13,596), mainly due to the three different-sized gravel layers used in the SSF substrate compared to the topsoil used in the FWS, which tripled the cost and placement time. The Total Annual Economic Cost (TAEC) was euro 1799/year and euro 1847/year for the FWS and SSF pair, respectively. TAEC was also used to compare the economic efficiency of the systems per cubic meter of HRO treated and kilograms of COD and TSS removed from the wetlands during their first operational year. Based on these estimations, FWS12 recorded the lowest TAEC(COD) and TAEC(TSS) values (euro 89.09/kg and euro 43.69/kg, respectively) compared to the other three systems, presenting a more economically favorable option.