Knowledge-based fuzzy system for diagnosis and control of an integrated biological wastewater treatment process

A supervisory expert system based on fuzzy logic rules was developed for diagnosis and control of a lab- scale plant comprising anaerobic/anoxic/aerobic modules for combined high rate biological N and C removal. The design and implementation of a computational environment in LabVIEW for data acquisition, plant operation and distributed equipment control is described. A step increase in ammonia concentration from 20 to 60 mg N/L was applied during a trial period of 73 hours. Recycle flow rate from the aerobic to the anoxic module and by-pass flow rate from the influent directly to the anoxic reactor were the output of the fuzzy system that were automatically changed (from 34 to 111 L/day and from 8 to 13 L/day, respectively), when new plant conditions were recognized by the expert system. Denitrification efficiency higher than 85% was achieved 30 hours after the disturbance and 15 hours after the system response at an HRT as low as 1.5 hours. Nitrification efficiency gradually increased from 12 to 50% at an HRT of 3 hours. The system proved to properly react in order to set adequate operating conditions that timely led to recover efficient N and C removal rates.Fundação para a Ciência e a Tecnologia , Fundo Social Europeu - BD/1299/2000 , BD/13317/2003

Municipal wastewater treatment with pond technology : historical review and future outlook

Facing an unprecedented population growth, it is difficult to overstress the assets for wastewater treatment of waste stabilization ponds (WSPs), i.e. high removal efficiency, simplicity, and low cost, which have been recognized by numerous scientists and operators. However, stricter discharge standards, changes in wastewater compounds, high emissions of greenhouse gases, and elevated land prices have led to their replacements in many places. This review aims at delivering a comprehensive overview of the historical development and current state of WSPs, and providing further insights to deal with their limitations in the future. The 21st century is witnessing changes in the way of approaching conventional problems in pond technology, in which WSPs should no longer be considered as a low treatment technology. Advanced models and technologies have been integrated for better design, control, and management. The roles of algae, which have been crucial as solar-powered aeration, will continue being a key solution. Yet, the separation of suspended algae to avoid deterioration of the effluent remains a major challenge in WSPs while in the case of high algal rate pond, further research is needed to maximize algal growth yield, select proper strains, and optimize harvesting methods to put algal biomass production in practice. Significant gaps need to be filled in understanding mechanisms of greenhouse gas emission, climate change mitigation, pond ecosystem services, and the fate and toxicity of emerging contaminants. From these insights, adaptation strategies are developed to deal with new opportunities and future challenges

A framework for modelling, simulation and control of integrated urban wastewater system

This paper is concerned with the integrated modelling, and control of urban wastewater systems (UWS) comprising the wastewater treatment plants (WTP), receiving waters (river) and the sewer networks. A unified framework is developed and simple models are used and implemented in Matlab/Simulink to produce a toolbox. Novel linear and nonlinear control structures are then proposed to design integrated control systems to improve the river water quality. A case study is simulated and simulation results are presented to demonstrate the possible improvement that can be achieved using a holistic integrated control system approac

Use of habitat suitability modeling in the integrated urban water system modeling of the Drava River (Varazdin, Croatia)

The development of practical tools for providing accurate ecological assessment of rivers and species conditions is necessary to preserve habitats and species, stop degradation and restore water quality. An understanding of the causal mechanisms and processes that affect the ecological water quality and shape macroinvertebrate communities at a local scale has important implications for conservation management and river restoration. This study used the integration of wastewater treatment, river water quality and ecological assessment models to study the effect of upgrading a wastewater treatment plant (WWTP) and their ecological effects for the receiving river. The WWTP and the water quality and quantity of the Drava river in Croatia were modelled in the software WEST. For the ecological modeling, the approach followed was to build habitat suitability and ecological assessment models based on classification trees. This technique allows predicting the biological water quality in terms of the occurrence of macroinvertebrates and the river status according to ecological water quality indices. The ecological models developed were satisfactory, and showed a good predictive performance and good discrimination capacity. Using the integrated ecological model for the Drava river, three scenarios were run and evaluated. The scenario assessment showed that it is necessary an integrated approach for the water management of the Drava river, which considers an upgrading of the WWTP with Nitrogen and Phosphorous removal and the treatment of other diffuse pollution and point sources (including the overflow of the WWTP). Additionally, if an increase in the minimum instream flow after the dams is considered, a higher dilution capacity and a higher self-cleaning capability could be obtained. The results proved that integrated models like the one presented here have an added value for decision support in water management. This kind of integrated approach is useful to get insight in aquatic ecosystems, for assessing investments in sanitation infrastructure of urban wastewater systems considering both, the fulfilling of legal physical chemical emission limits and the ecological state of the receiving waters

WETWALL - an innovative design concept for the treatment of wastewater at an urban scale

Rising temperatures, increasing food demand and scarcity of water and land resources highlight the importance of promoting the sustainable expansion of agriculture to our urban environment, while preserving water resources. Treating urban wastewaters, such as greywater and hydroponic wastewater, may represent a strategic point for the implementation of urban farming, ensuring food security, reducing pressures on water resources and promoting climate change mitigation. The WETWALL design concept proposes a unique ecotechnology for secondary wastewater treatment at an urban scale, which brings the novelty of a modular living wall hybrid flow. This concept is based on the integration of two established nature-based solutions/ecomimetic designs: constructed wetlands and a modular living walls. First presented is an overview about the state of the art in the scope of living walls treating wastewater, in order to identify the main design aspects related to the performance of such systems, which mainly concerns the removal of nitrates and phosphates. Second, the WETWALL design concept is presented. A scheme regarding the selection of the main components, such as plants and substrate, is proposed, and potential structure developments and operation strategies are discussed. In addition, considering the scope of integrating the circular economy with the design process, potential interactions between this technology and the urban environment are discussed. The main goal of this article is to substantiate the potential of the WETWALL design concept as an innovative wastewater treatment at an urban scale.Biggest thanks to the National Council for Scientific and Technological Development – Brazil (CNPQ), for their financial support (doctoral fellowship). The authors also would like to thank the UNESCO Chair on Sustainability of the Polytechnic University of Catalonia (Spain), the Aarhus University (Denmark) and the research groups GREA (2014 SGR 123), DIOPMA (2014 SGR 1543) and GICITED (2014 SGR 1298)

ZeroWasteWater: short-cycling of wastewater resources for sustainable cities of the future

Sewage treatment relies mainly on conventional activated sludge (CAS) systems, reaching sufficiently low pollutant effluent levels. Yet, CAS has a low cost-effectiveness and recovery potential and a high electricity demand and environmental footprint. By 2050, globally we have to solve severe water and phosphorus shortages while significantly decreasing greenhouse gas emissions. In this review and opinion paper, the ZeroWasteWater concept is proposed as a sustainable centralised technology train to short-cycle water, energy and valuable materials from sewage, while adequately abating pathogens, heavy metals and trace organics. Electrical energy recovery from anaerobic digestion of the organics present in sewage and kitchen waste (KW) has a value of 4.0 per inhabitant equivalent (IE) per year. In addition to sewerage improvements and water conservation, prerequisites include an advanced physico-chemical and/or biological concentration step at the entry of the sewage treatment plant. In the side stream, the recovery of phosphorus and carbon-sequestrating biochar from the digested sludge and of nitrogen from the digestate has a value of 6.3IE-1 year-1. Alternatively, recovery of biogas and materials can occur directly on source-separated black water. In the main stream, partial nitritation and anammox oxidise residual nitrogen. Moreover, two serial heat pumps recover thermal energy, valued at 6.9IE-1 year-1, cooling the water by 5 degrees C, and membrane technologies recover potable water at 65IE-1 year-1. Interestingly, ZeroWasteWater is expected to be economically viable. Key steps are to incorporate water chain management into holistic urban planning and thus produce a cradle-to-cradle approach that society will find acceptable