The operational flexibility of Sequencing Batch Reactors (SBR) makes this technology especially resilient to changes in functional requirements. A main feature of SBRs is that plant upgrading from nitrogen to phosphorus removal specifications becomes straightforward by simple adaptation of the manipulated variables. In contrast, the optimum design and operation of these processes is an intricate problem whose formulation involves multiple considerations such as mathematical descriptions for both biological transformations and solids separation phenomena, design procedures for air diffusers, etc. Moreover, the dynamic nature of SBRs adds extra complexity when it comes to solving optimization problems for this technology. In this paper, a model-based optimization framework is proposed to solve the optimum design and operation of SBR systems. This framework splits the whole problem into two single objective optimization sub-problems. The dimensions of the SBR are first calculated; Then, the operational costs in the long-term are optimized. A case-study for a population of 100000 inhabitant-equivalent demonstrates the potential of the framework.

This study explored the potential of acidogenic fermentation of sewage sludge (SS) in an 80 L automatized pilot scale platform. A high-rate VFA production was obtained at HRT 5d and pH 9, with a volatile fatty acid (VFA) yield of 336 mg VFA g(-1) VS and a VFA productivity of 2.15 kg VFA m(-3) d(-1). During co-fermentation of SS with OFMSW, a reversible pH shift from pH 9 to pH 6, evidenced a higher acidogenic activity which promoted the butyrate metabolic pathway, with 13.97 g COD L-1 of butyric acid and a VFA peak 23.2 g COD L-1. The results show the degree of flexibility of mixed culture fermentation systems, where other pH control methods other than steady control could be used to enhance the fermentation process. Ultrafiltration was a feasible technology to obtain a VFA rich permeate where 12.3-26.6 g COD L-1 could be recovered.

Advanced real time - Instrumentation, Control, and Automation (Art-ICA) controllers are an advanced control solution for biological nutrient removal wastewater treatment plants. Art-ICA has been previously shown to be capable of enhancing nutrient removal performance in BNR plants, at lower energy expenditures. However, the impact that this control solution has on the greenhouse gas emissions from full-scale wastewater treatment plants has not previously been addressed. This work addresses the effect of art-ICA on the performance, energy consumption and greenhouse gas emissions of two full-scale WWTPs, Chelas and Castelo Branco (Portugal). The raw wastewater, nitrous oxide emissions, energy consumption and water discharges were quantified in two independent trains operated under different operational modes, conventional operation and art-ICA control. The implementation of the art-ICA strategy improved the effluent quality and reduced the operational costs, resulting in a better performance of these WWTPs. The art-ICA controllers activation led to a reduction of 54% and 7-10% of the total nitrogen effluent and in the specific energy consumption, respectively. Moreover, process control with art-ICA did not have a negative impact on the N2O emissions of the plants, and contributed to lower global warming potential by the facilities. The lower indirect carbon dioxide production due to lower energy consumption contributes to the observation that art-ICA control is environmentally preferable to conventional control. (C) 2018 Elsevier Ltd. All rights reserved.

Volatile fatty acid (VFA) production through anaerobic fermentation may constitute an innovative solution for organic waste management within the context of circular economy. In the present study, the evolution of individual VFA during laboratory-scale fermentation of sewage sludge (SS), winery wastewater (Www) and meat and bone meal (MBM) was assessed, focusing on the effect of pH (5.5 and 10) and temperature (35 and 55 degrees C). Up-scaling of the fermentation process was evaluated in batch operation. The latter showed that specific VFA could be produced, giving similar individual evolution to lab-scale testing. To be precise, acetic acid percentage ranged within 30-65% and increased up to 5900 mg O-2 L-1 during SS fermentation at 55 degrees C and pH 9. In addition, 60% butyric acid was reached during Www acid fermentation at 55 degrees C, which corresponded to 6670 mg O-2 L-1 concentration in the fermentation broth. Regarding valeric acid, over 20% proportion and 2700 mg O-2 L-1 were reached in MBM acid fermentation at 35 degrees C. Finally, iso-valeric maximum level ranged within 15-17% in SS alkaline fermentation at 55 degrees C, which represented a concentration close to 2000 mg O-2 L-1. Interestingly, co-fermentation of agri-food waste and SS at thermophilic temperature and alkaline pH, boosted the VFA concentration 1.7-2 fold, which suggests that anaerobic co-fermentation of substrates from different nature could give promising outcomes in full-scale operation.

Internal Circulation (IC) anaerobic systems are especially suitable when plant designs that involve both small footprints and high organic loading rates (>25 kg COD m(-3) d(-1)) are required. However, given that operating anaerobic processes at high organic loads increases their vulnerability to external disturbances, real-time indicators of the stability conditions become particularly pertinent for IC reactors. This paper addresses the design and full-scale validation of a software sensor that uses only feeding flow-rate and biogas flow-rate measurements to classify the operating conditions of the reactor as "strongly", "moderately" or "weakly" stable. A simulation-based procedure was used to design the software sensor and configure its parameters. Then, the performance of the software sensor was tested under real conditions in a full-scale IC reactor of 1679 m(3) installed in a recycled paper mill (RPM). (C) 2018 Elsevier Ltd. All rights reserved.

The literature shows a diversity of real-time algorithms for automatic detection of bending-points in batch-operated waste treatment systems. In this study a new methodology is proposed for tuning the parameters of these algorithms when uncertainty specifications are considered at the outset. In this method the effects of slow and fast dynamic responses on the shape of signal trajectories were treated separately in order to cover via simulation all possible operating scenarios for a real situation. Long-term uncertainty and steady-state simulations were combined to derive probability distributions for biomasses. These probability distributions were then merged with short-term uncertainty to run one-cycle random simulations with which to reproduce the entire diversity of signal trajectories. Finally, an optimisation problem was formulated in terms of the algorithm parameters. The methodology was satisfactorily applied to tune an algorithm for detection of bending-points in an Autothermal Thermophilic Aerobic Digestion (ATAD) process. (C) 2015 Elsevier Ltd. All rights reserved.

Although often perceived as tools for use by scientists, mathematical modelling and simulation become indispensable when control engineers have to design controllers for real-life wastewater treatment plants (WWTPs). Nonetheless, the design of effective controllers in the wastewater domain using simulations requires effects, such as the nonlinearity of actuators, the time response of sensors, plant model uncertainties, etc. to have been reproduced beforehand. Otherwise, control solutions verified by simulation can completely underperform under real conditions. This study demonstrates that, when all the above effects are included at the outset, a systematic use of simulations guarantees high quality controllers in a relatively short period of time. The above is exemplified through the Mekolalde WWTP, where a comprehensive simulation study was conducted in order to develop a control product for nitrogen removal. Since its activation in May 2011, the designed controller has been permanently working in the plant which, from this time onwards, has experienced significant improvements in the quality of water discharges combined with a lower utilization of electricity for wastewater treatment.

The benefits of upgrading extremum-seeking controllers with an effective exploitation of the buffer capacity of equalization tanks have been investigated and applied to anaerobic digesters. In this respect, a Fuzzy-based supervisory module that monitors the state of the equalization tank has been designed and built on top of an extremum-seeking algorithm in charge of automatically regulating the wastewater fed into the anaerobic digester. The extremum-seeking controller guarantees good disturbance rejection and methane production around an upper limit set-point. The on-top Fuzzy module optimizes the long-term methane production by modifying this upper limit set-point as a function of the state of the equalization tank. A systematic simulation study has been carried out to evaluate the performance of the proposed control solution. Thus, on the basis of existing simulation benchmarks for assessment of control strategies in wastewater treatment plants, a dedicated simulation protocol for anaerobic digesters has been defined and implemented. Simulation results have shown that, compared with manual operation, effluent quality and methane production improvements of 10-15% are achieved using the proposed control approach.

The principles of economic evaluation and cost benefit analysis implemented in sewage treatment plants; Economic evaluation of innovative technologies aiming to increase the energy efficiency of the sewage treatment plants; Instrumentation, monitoring and real-time control strategies for efficient sewage treatment plant operation; Process integration to improve carbon, nitrogen and phosphorus removal with less aeration requirements and less sludge production; Bioreactor development with less aeration requirement; Improvement of anaerobic digestion of sewage wastewater and sludge; Development of microbial fuel cells for electricity production from sewage; Nutrient recovery from sewage; Cost saving management strategies or policies; Economic evaluation of innovative technologies aiming to increase the energy efficiency of the sewage treatment plants: Case studies.