The aim of this work was to evaluate the performance of a UASB-septic tank as a decentralized treatment of high-strength municipal wastewater under two different HRTs (48 and 72 h). Thus, a lab-scale (44.85 L) UASB-septic tank constituted by three compartments was operated under HRT 72 and 48 h. Removal efficiencies of total chemical oxygen demand (COD), biological oxygen demand (BOD) and suspended solids (SS) ranged from 60% to 80% for the first two parameters and from 70% to 90% for the last one. According to the statistical analysis, it was established that decreasing HRT from 72 to 48 h did not affect the performance of the UASB-septic tank; therefore, the latter HRT is recommended to be used for operation. In the first compartment, most of the organic matter removal was carried out, while the other two compartments served as polishing. Over the course of six months, the VS concentration and VS/TS ratio in sludge blanket decreased, indicating digestion and stabilization of the retained solids. Also, an increase of 4% in sludge volume was observed; thus, time for desludging would be approximately five years. Comparison of the UASB-septic tank and the UASB reactor showed that both systems had similar performance regarding effluent concentrations of organic matter and solids. Thus, under low volumetric organic load conditions (less than 20 mg COD/L h), the former is an attractive option for municipal wastewater treatment.
The objective of this work was to assess the performance during the start-up phase of a Upflow anaerobic sludge blanket (UASB)-septic tank for municipal wastewater treatment in Mexico City. A lab scale UASB-septic tank (62 L total volume, acrylic), consisting of three chambers treated high strength municipal wastewater at ambient temperature (16 °C–24 °C), under 72 h Hydraulic retention time (HRT) during three months. Total and soluble chemical oxygen demand (COD), total biological oxygen demand (BOD5), total solids and total suspended solids (TSS) removals were 75.2 ± 6.5%, 54.8 ± 6.7%, 64.2 ± 4.8%, 25.9 ± 5% and 82.9 ± 5%, respectively. These results are comparable with the removals reported in other works with similar arrangements; and are similar even with average removals of COD, BOD and TSS in UASB reactors installed in Latin America. The good performance obtained showed that it is possible to achieve a short start-up period with UASB-septic tank if it is inoculated with anaerobic sludge. These findings also evidenced the feasibility and reliability of the UASB-septic tank system for decentralized wastewater management in Mexico.
This work analysed the hydraulic behaviour and treatment efficiency of an upflow baffled septic tank (UBST) through tracer tests and mathematical modelling using the axial dispersion and the tank‐in‐series (TIS) models. The tracer tests were performed under different HRTs (12, 18 and 24 h) and configurations (UBST, UBST with sludge and UBST with sludge and zeolite filter). UBST followed a non‐ideal flow, and configuration modifications, rather than HRT, altered its hydraulic behaviour. Mathematical modelling indicated that the TIS model calculated with mean squared error (φ) described adequately UBST hydraulic behaviour (R2 = 0.9833). Additionally, UBST is recommended to operate under 24 h HRT to reach satisfactory hydraulic and pollutant removal efficiencies. At this HRT, total COD and ammonium removals were 75.1% and 49.3%, respectively, which were better than those obtained without the zeolite (71.2% and 1.8%, respectively). However, it quickly saturated, so it is necessary to deepen the research on this topic.
ResumenEl objetivo de este trabajo fue determinar la constante de velocidad (K), los coeficientes de rendimiento celular (Y) y de decaimiento endógeno (ke) y algunos parámetros operacionales para el diseño de un reactor UASB a escala real para el tratamiento de las aguas residuales municipales generadas en el campus de la Universidad Autónoma Metropolitana -Azcapotzalco. Para este fin, un reactor UASB a escala de laboratorio fue operado bajo cuatro TRH diferentes (4, 6, 8 y 12 h) durante seis meses. La remoción de la DQO total varió entre 50% al TRH de 4 horas hasta un 75% al TRH de 12 horas, se obtuvieron resultados similares con los parámetros de DBO 5 y SST. Una prueba t de Student apareada mostró que la remoción de DQO obtenida con los cuatro TRH estudiados fue significativamente diferente al TRH de 12 horas; por lo tanto, se recomienda este TRH para el diseño del reactor Palabras clave: Agua residual municipal, Coeficientes cinéticos, degradación anaerobia. AbstractThe aim of this study was to determine the rate constant (K) coefficients cell yield (Y) and endogenous decay (ke) and some operational parameters for the design of a UASB reactor-scale for water treatment residual municipal generated on the campus of the Universidad Autonoma Metropolitana -Azcapotzalco. To this end, a UASB reactor
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