Treatment and monitoring of Water

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The moderator of this session is: Huub Rijnaarts (Professor, Environmental Technology, Wageningen University and Research)

This session will include the speakers: Siddhart Seshan (KWR Water Research Institute, The Netherlands), Christian Linnartz (RWTH Aachen University and DWI Leibniz Institute for Interactive Materials) and Marjan Joris (iFLUX)

Take a look at the abstracts below:

Robust Wastewater Characterisation for the Development of a Biokinetic-Artificial Intelligence Hybrid Model to Reduce Nitrous Oxide Emissions

Presenting author: Siddhart Seshan

Nitrous oxide (N2O), is considered a potent and very harmful greenhouse gas (GHG); in addition, N2O is also considered to contribute to the depletion of the ozone layer in the stratosphere. With the global warming potential of N2O being as high as 298 times greater than that of CO2 on a 100-year time scale, identifying and mitigating the anthropogenic sources of N2O is crucial in curbing its harmful environmental effects. In the past decade, wastewater treatment plants (WWTPs) are increasingly considered to be one of the potent sources of N2O, and therefore, advance wastewater treatment technologies and operational strategies to reduce the generation of the harmful N2O gas are being investigated. For that purpose, a clear understanding and representation of the process conditions in the system is necessary in order to investigate mitigation measures. One such approach that can be utilized is in the form of a biokinetic model, using widely known Activated Sludge Models (ASMs) that have been extended to include the N2O production pathways. In parallel, Artificial Intelligence (AI) models have also been utilised in the prediction of key wastewater parameters including N2O in data-rich systems. However, in the N2O field, hybrid models comprising the biokinetic and AI models have not yet been developed. Such hybrid models could allow for the biokinetic model features to provide process insights while the AI models can enable (near) real-time estimation and control of the treatment processes in order to achieve the reduction of N2O emissions. In our present research, as a prelude to the development of the hybrid model, a biokinetic model is being built and calibrated for the Amsterdam West WWTP using the EnviroSim software, BioWin®. In order to acquire the data necessary to input into the model, a comprehensive and intensive sampling campaign was conducted. The campaign’s duration was for 8 days. Flow proportional daily composite samples and diurnal sampling were taken for the raw influent and effluent wastewater where the following parameters were monitored – CODtotal, CODfiltered, BODtotal, BODfiltered, TKN, NH4, NO3, Total P, Ortho-PO4, ISS and TSS. The raw influent was also periodically monitored for pH, Alkalinity, Ca, Mg and Total Sulphide. The diurnal sampling was conducted on one weekday and weekend day. Numerous grab samples were also taken at various locations including the anaerobic, anoxic and aerobic zones of the bioreactor, sludge treatment lines and filtrate streams. The grab sampled data provide a sanity check for the outputs provided by the biokinetic model. With the execution of the comprehensive monitoring campaign, the sampling data can now characterise the common quality measurements (COD, TKN, TP, TSS, etc.) into their fractions as required for use in the biokinetic models and can now be mapped into the BioWin ASDM inputs. Additionally, Amsterdam West WWTP is a large plant, with a capacity of 1.1 million population equivalent. Therefore the logistics in conducting a monitoring campaign of such scale was complex, time consuming and labour intensive. Another key insight is that sampling during periods of normal and stable plant operation provides the most reliable results of wastewater characteristics. In addition, increasing the number of samples can help partially overcome the adverse impacts on sampling results from occasional period of unusual plant operation and control.

Keywords: nitrous oxide; wastewater treatment; sampling; modelling; reduction

From Lab to Application: Flow-electrode Capacitive Deionization

Presenting author: Christian Lennarts

Flow-electrode capacitive deionization (FCDI) is a novel water treatment process based on the capacitive deionization (CDI) technology. FCDI, however, makes use of flowable carbon suspension electrodes, which enable continuous CDI operation and overcome the limitations of static CDI electrodes in terms of energy efficiency and application range. These flow-electrodes are usually based on activated carbon powder suspended in aqueous salt solutions. As a result, FCDI can be adapted to treat water with a wide range of salinities and to address a wide range of issues and challenges, such as:

pollutions  from  salt  emissions  by  effluent  streams  into   the   environment   (e.g.   nitrate); economical infeasibility of the reuse of valuable salts (e.g. lithium salts) due to low solution concentrations or solubility limits in wastewaters.

FCDI is an innovative and energy-efficient technology to reuse, recover and recycle materials. FCDI applies an electric field to drive ions selectively from the water solutions to the flow electrodes, producing a purified water stream. The ions are subsequently discharged from the flow electrodes into a concentrated water stream. Both steps occur in parallel, resulting in a fully continuous process. In contrast to other desalination and concentration technologies, the approach is advantageous for the treatment of fouling/scaling-prone solutions, as it separates the ions without treatment of the water phase.

As the inventors of the first fully continuous FCDI systems worldwide, our group have investigated and developed the FCDI technology intensively over the last years. Now, we are about to apply FCDI on the pilot scale for industry applications as a safe resource recovery technology. This talk will summarize our efforts and results of developing a new technology on the lab scale for various applications that aim to close the material cycles in industries. The talk will also give a deep look into our progress of scaling up the system into a pilot plant.

Real time monitoring of groundwater flux creates insight in the complex water system of Romboutswerve Polder in Damme, Belgium

Presenting author: Marjan Joris

A pilot real time monitoring network is installed in the Romboutswerve polder which is a protected nature reserve of 140 hectares as a habitat of bird species and of international importance for wintering of migratory birds. The dewatering of the peaty soil caused the land to subside. More elevated zones are the result of a more sandy soil, less inclined due to the dewatering. The lower areas are used as grassland and elevated areas as farmland. To the south and the ouest of the polder are the cities of Damme and Bruges. The area is partly bounded by canals and crossed by a multitude of canals and ditches that either drain or feed the area. The waterways are both of marine origin and man-made. The area is threatened by drought. Although after periods of intense rainfall, the water has to be discharged to protect the higher urban areas from flooding, so that there is currently little possibility of water retention and pastures are hardly flooded, even in winter. The challenge is to redevelop the area and optimize water management to tackle the consequences of climate change taking into account the different types of land use in the area and preserve or improve biodiversity. Groundwater dynamics plays a crucial role in the field of ecosystem restoration. Dynamics are often underestimated or even not taken into acount. There is still a big gap in understanding groundwater flow dynamics although they are crucial for succesfull development and management of restoration projects. Traditional monitoring networks follow up groundwater levels which are only the result of the in’s and outs of the water system. These groundwater levels are used to callibrate complex models simulating groundwater flow, without knowlegde of the causes behind. Simulated groundwater flow is always an approximation of reality, often a simplification, which can lead to misinterpretation. Measuring groundwater flow on site helps to understand the water system and its dynamics. The installed real time groundwater monitoring network includes the unique iFLUX sensors for horizontal and vertical groundwater flux in combination with a weather station, level sensors and CTD sensor. Surface water levels provided by third partie are also added. The combined data allow to see interaction and correlation between weather events, groundwater flow velocity and -direction and the levels of ground- and surface water. The pilot test already created new insights in the total water balance of the Romboutswerve Polder. Examples of these insights are reversing of the horizontal flow direction in case of in- of decrease of the exfiltration flow and a clear upward seapage which needs further investigation. Based on these first results we plan to expand monitoring and setup restoration pilots to quantify the infiltration and retention capacity. The monitoring network allows to identify the water balance, the effects but also the causes. Effective monitoring and quantifying the results of restoration measurements will help to convince different stakeholders and will lead to a effective restorationbased on a comprehensive water management.

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