Abstract
Systems combining anaerobic bioreactors with constructed wetlands (CW) have proven to be adequate and efficient for wastewater treatment. Detailed knowledge of removal dynamics of contaminants can ensure positive results for engineering and design. Mathematical modeling is a useful approach to studying the dynamics of contaminant removal in wastewater. In this study, water quality monitoring was performed in a system composed of a septic tank (ST), an up flow anaerobic filter (UAF), and a horizontal flow constructed wetland (HFCW). Biological oxygen demand (BOD5), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), NH3, organic nitrogen (ON), total suspended solids (TSS), NO2−, and NO3− were measured biweekly during a 3-month period. First-order kinetics, multiple linear regression, and mass balance models were applied for data adjustment. First-order models were useful to predict the outlet concentration of pollutants (R2 > 0.87). Relevant multiple linear regression models were found, which could be applied to facilitate the system’s monitoring and provide valuable information to control and improve biological and physical processes necessary for wastewater treatment. Finally, the values of important parameters (μmax, Ks, and Yx/s) in mass-balance models were determined with the aid of a differential neural network (DNN) and an optimization algorithm. The estimated parameters indicated the high robustness of the treatment system since performance stability was found despite variations in wastewater composition.
Highlights
The development of adequate technologies for wastewater treatment in developing countries is urgent to minimize environmental degradation and satisfy water supply necessities [1]
The highest performance in terms of solids removal was found in the septic tank (ST), which eliminated 257.7 ± 65.2 mg/L of total suspended solids (TSS), while up flow anaerobic filter (UAF) and horizontal flow constructed wetland (HFCW) eliminated 38.8 ± 15.0 mg/L and 42.5 ± 11.4 mg/L, respectively. These results prove that the ST efficiently fulfills its function of preventing the accumulation of solid particles in the UAF and the HFCW, avoiding obstruction, which is one of the main problems present in this type of system after long periods of operation [43]
For all nitrogenous parameters (TKN, NH3, and organic nitrogen (ON)), the results were very similar in range and comparable to those reported by other studies in constructed wetlands (CW), ANNAMOX processes, and anaerobic reactors [17,26,62,63,64]. These results prove the efficiency of the system for nitrogen removal in the HFCW and in the anaerobic reactors ST and UAF
Summary
The development of adequate technologies for wastewater treatment in developing countries is urgent to minimize environmental degradation and satisfy water supply necessities [1]. Development Goal number six of the United Nations is dedicated to clean water and sanitation It seeks to substantially improve water quality by increasing the safe reuse and recycling of water systems and lowering the release of pollutants and toxins into wastewater by the year 2030 [2]. Water 2020, 12, 3019 wastewater generated by large communities and cities These systems often collect/treat/reuse/dispose of wastewater far from the generation point; they require large pipes, major excavations, and manholes for access [3]. These systems normally require high amounts of energy due to the complex operation of mechanical, chemical, and biological processes used to remove contaminants in the sewage. On the other hand, the collection, treatment, and reuse/disposal of wastewater is fulfilled on site or near the generation point [3]
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