Software sensors, or soft sensors, can be a feasible option to monitor parameters that are difficult (or impossible) to measure with hardware sensors. At Henriksdal water resource recovery facility (WRRF), the operators have long experienced issues with a clogging sensor for the dry solid (DS) content in thickened primary sludge. A soft sensor was developed, and in the process, two methods were compared: long short-term memory (LSTM) network and linear regression. The first is a recurrent neural network that can capture non-linear dynamics, whereas the latter is a linear static model. The LSTM network was the best at predicting the DS content, with a mean squared error (MSE) of 0.341 with respect to laboratory data. The linear regression model performed worse than estimating a long-time average of daily manual samples but outperformed the online sensor. Replacing the existing sensor with the developed soft sensor can open up possibilities for more efficient control and operation of the thickener unit.

Digital twins have been gaining an immense interest in various fields over the last decade. Bringing conventional process simulation models into (near) real time are thought to provide valuable insights for operators, decision makers, and stakeholders in many industries. The objective of this paper is to describe two methods for implementing digital twins at water resource recovery facilities and highlight and discuss their differences and preferable use situations, with focus on the automated data transfer from the real process. Case 1 uses a tailor-made infrastructure for automated data transfer between the facility and the digital twin. Case 2 uses edge computing for rapid automated data transfer. The data transfer lag from process to digital twin is low compared to the simulation frequency in both systems. The presented digital twin objectives can be achieved using either of the presented methods. The method of Case 1 is better suited for automatic recalibration of model parameters, although workarounds exist for the method in Case 2. The method of Case 2 is well suited for objectives such as soft sensors due to its integration with the SCADA system and low latency. The objective of the digital twin, and the required latency of the system, should guide the choice of method. PRACTITIONER POINTS: Various methods can be used for automated data transfer between the physical system and a digital twin. Delays in the data transfer differ depending on implementation method. The digital twin objective determines the required simulation frequency. Implementation method should be chosen based on the required simulation frequency.

Activities that require a permit in Sweden account for a significant part of the environmental impact that jeopardizes the fulfilment of the 16 Swedish National Environmental Quality Objectives (EQOs) set up by the Swedish Parliament. In this study we investigate how the EQOs are perceived as a management tool in the Swedish Environmental Impact Assessment (EIA) process, mainly based on interviews. We have identified several limitations associated with the use of EQOs in EIAs as an effective management tool towards sustainability. These limitations include that the EQOs have a subordinate significance compared with other aspects in the EIA process and that EQOs represent different concepts of sustainability. Furthermore, EQOs have low validity and are set as national objectives, hence separated from the operational level of EIAs. A significant proportion of environmental pressures leading to failure to achieve the EQOs are related to permit requiring activities, hence EIA and the permitting process can be important policy instruments to achieve the Swedish EQOs. Integrating EQOs better into EIAs may facilitate handling of synergies, inconsistencies, and trade-offs between environmental and sectoral objectives. Furthermore, driving forces of environmental problems may be targeted more directly. However, in order for the Swedish EQOs to have a larger impact in the permitting process, the EQO system may need to be adapted, and may also need to be complemented with binding standards or legal norms. Furthermore, clearer guidelines regarding issues to focus on, and necessary templates and documentation may be useful tools to facilitate the process even further.

Public acceptance of environmental compensation (offsetting) as a mechanism to address negative human impacts on biodiversity and ecosystem services is critical. Given that "in-kind/on-site" compensation is rarely possible, proposals must address trade-offs with respect to design. We measure Swedish citizens' support for compensation and analyze preferences for design attributes based on a choice experiment in which respondents choose between various compensation alternatives to address the hypothetical loss of green space due to urban development. We find citizens' support for compensation is high, but the activity causing the damage affects acceptance. Our model suggests that several design attributes affect choice but size of the compensation area was valued highest, both in relative and absolute terms. Further, our results suggest that compensation should be primarily focused on creating or improving biodiversity and nature values in order to be in line with public preferences. Additionally, choice depends on interactions between attributes: a larger compensation site matters more when it is relatively further away; and the importance of size and distance from damage depends on whether compensation type focuses on nature or recreational values. Observable characteristics such as a respondent's age, income and education affect compensation design preferences, but perceptions and previous experiences have the largest effect on choice. Our findings suggest that public preferences are consistent with many of the general recommendations found in guidance documents, but local context may argue for alternative priorities with respect to certain species, habitats, and/or the wellbeing of certain groups. To engender broad support, compensatory offsets will need to balance scientific rigor with transparent involvement of the public.

This study finds that industries and other permit requiring activities (PRA) exert a significant cumulative pressure on 20 out of 34 examined specifications to the Swedish Environmental Quality Objectives (EQO), affecting the fulfilment of 12 out of 16 of these EQOs. PRA undergo thorough examination before receiving permits, and the permits come with detailed conditions. The permitting process is hence an important opportunity to contribute to the achievement of the EQOs. However, this opportunity has so far not been employed to any great extent since the quantitative significance of environmental impact from PRA on the national EQOs has not been well-known or expressed. We suggest that quantification of activities that can be regulated by environmental permitting may be of importance for the achievement of other instances of management by objectives in general, such as the global sustainable development goals and the EU Marine Strategy Framework Directive and the ecological status regulated by the European Water Framework Directive.

This study highlights the need to increase our understanding of the interplay between sensor drift and the performance of the automatic control system. The impact from biased sensors on the automatic control systems is rarely considered when different control strategies are assessed in water resource recovery facilities. Still, the harsh measurement environment with negative effects on sensor data quality is widely acknowledged. Simulations were used to show how sensor bias in an ammonium cascade feedback controller impacts aeration energy efficiency and total nitrogen removal in an activated sludge process. Response surface methodology was used to reduce the required number of simulations, and to consider the combined effect of two simultaneously biased sensors. The effects from flow variations, and negatively biased ammonium (-1 mg/L) and suspended solids sensors (-500 mg/L) reduced the nitrification aeration energy efficiency by between 7 and 25%. Less impact was seen on total nitrogen removal. There were no added non-linear effects from the two simultaneously biased sensors, apart from an interaction between a biased ammonium sensor and dissolved oxygen sensor located in the last aerated zone. Negative effects from sensor bias can partly be limited if the expected bias direction is considered when the controller setpoint-limits are defined.

Environmental compensation (EC) aims at addressing environmental losses due to development projects and involves a need to compare development losses with compensation gains using relevant metrics. A conceptual procedure for computing no net loss is formulated and used as a point of departure for a comparative analysis of metrics used by five Swedish municipalities as a part of their EC implementation in the spatial planning context of detailed development plans. While Swedish law does not require EC in this context, these municipalities have still decided to introduce EC requirements for development projects that occur on municipality-owned land and to promote voluntary EC among private actors in development projects on private land. There is substantial variation across the municipalities studied with respect to both metrics and attributes subject to measurement, but there are also similarities: The attributes considered when assessing the need for EC in conjunction with development are not only about nature per se, but also about recreational opportunities and other types ecosystem services; semi-quantitative metrics such as scores are common while quantitative or monetary metrics are rare; and metrics are rarely applied to assess compensatory gains, focusing instead on losses from development. Streamlining across municipalities might be warranted for increasing predictability and transparency for developers and citizens, but it also introduces considerable challenges such as a need for developing consistent guidelines for semi-quantitative metrics, and to handle substitutability issues if metrics are not only applied on individual attributes but also on groups of attributes. The broad scope of attributes used by the municipalities is in line with an international tendency to broaden EC to include not only biodiversity aspects but also ecosystem services. Moreover, the EC systems applied by the municipalities are of particular importance for highlighting the crucial role of environmental management for maintaining and enhancing biodiversity and ecosystem services not only in areas having formal protection status but also in the everyday landscape. The municipalities’ experience and strengths and weaknesses associated with their EC systems are therefore relevant also in an international perspective.

There are many important linkages between land, freshwater and oceans. Source-to-sea (S2S) management has been proposed to support environmental management that considers interests along the S2S continuum. This study takes the Bohai and Baltic seas as examples to analyse the legislation system, administrative structure and stakeholders of freshwater and marine management in China and the European Union and presents the related challenges and opportunities for S2S management. The results of this study can provide a basis for designing initiatives to support healthy ecosystems and sustainable green and blue economies, reduce the burdens on water-related ecosystems, and improve economic opportunities and livelihoods.

In the struggle to reach the national environmental policy objectives, environmental compensation has emerged as a possible policy tool that may contribute to achieving the objectives. In Sweden, environmental compensation is legally mandated mainly in cases of exploitation within Natura 2000 areas and nature reserves, which is handled through the Swedish Environmental Code. In contrast, regulatory support is weak when it comes to compensation for impacts arising from municipal development (e.g., housing, schools, hospitals, local roads, etc), even though detailed development planning is required through the Planning and Building Act. Despite this, some municipalities have voluntarily mainstreamed environmental compensation into their planning processes. In the research project ”MuniComp” (2018-2020) we investigate the more progressive use of environmental compensation in planning in two Southern Swedish municipalities, Lomma and Helsingborg (in the province of Skane). We analyze the models and processes of compensation used, and planning cases where compensation have been applied, in terms of general aspects and criteria for environmental compensation and in light of the constraints of the Swedish legislative context. In the presentation, the compensation models and some of the results from the compensation cases will be presented. (Less)

Det projekt som redovisas i denna rapport har undersokt hur ekosystemtjanster har hanterats, och kan komma att foras in, i beslutsunderlag for infrastrukturplanering framover. Fokus for analysen ...

Given the growing number of policies and laws that encourage inclusion of ecosystem services (ES) in processes, we have investigated environmental impact assessments (EIA) and strategic environmental assessments (SEA) conducted in Sweden in order to analyse whether ES maybe integrated to enhance and improve environmental assessment of today. Representative Swedish environmental projects were reviewed. Three cases with different geographic and environmental settings were selected to allow us to study consideration of a wide range of different ES. We investigated the processes and discussions taking place using documentation from the cases. We formalized and labelled the expected impacts into an ES framework. Summarizing each case, we described conformities and divergences in explicit and implicit prioritizations between the actors. We discussed the benefits of integrating ES into current practices and possible improvements in the processes and methodologies. When ES could be integrated into EIAs and SEAs more aspects would be visualized and a larger stakeholder engagement stimulated leading to improved support for decision-making.

In this paper, a sensitivity analysis and a calibration were applied to a recent published model used to replicate N2O emissions in an Anammox process of a moving-bed biofilm reactor (MBBR). The mo ...

Ekosystemtjanster kan bidra till att synliggora varden i naturen som manniskor ar beroende av for sin overlevnad och sin valfard. Att integrera ekosystemtjanster i miljokonsekvensbeskrivningar och ...

SIMULATING THE ENVIRONMENTAL IMPACT OF STRICTER NITROGEN AND PHOSPHOROUS DISCHARGE CRITERIA

The objective of this paper was to show the potential additional insight that result from adding greenhouse gas (GHG) emissions to plant performance evaluation criteria, such as effluent quality (EQI) and operational cost (OCI) indices, when evaluating (plant-wide) control/operational strategies in wastewater treatment plants (WWTPs). The proposed GHG evaluation is based on a set of comprehensive dynamic models that estimate the most significant potential on-site and off-site sources of CO2, CH4 and N2O. The study calculates and discusses the changes in EQI, OCI and the emission of GHGs as a consequence of varying the following four process variables: (i) the set point of aeration control in the activated sludge section; (ii) the removal efficiency of total suspended solids (TSS) in the primary clarifier; (iii) the temperature in the anaerobic digester; and (iv) the control of the flow of anaerobic digester supernatants coming from sludge treatment. Based upon the assumptions built into the model structures, simulation results highlight the potential undesirable effects of increased GHG production when carrying out local energy optimization of the aeration system in the activated sludge section and energy recovery from the AD. Although off-site CO2 emissions may decrease, the effect is counterbalanced by increased N2O emissions, especially since N2O has a 300-fold stronger greenhouse effect than CO2. The reported results emphasize the importance and usefulness of using multiple evaluation criteria to compare and evaluate (plant-wide) control strategies in a WWTP for more informed operational decision making.

The objective of this paper is to demonstrate the full-scale feasibility of the phenomenological dynamic influent pollutant disturbance scenario generator (DIPDSG) that was originally used to create the influent data of the International Water Association (IWA) Benchmark Simulation Model No. 2 (BSM2). In this study, the influent characteristics of two large Scandinavian treatment facilities are studied for a period of two years. A step-wise procedure based on adjusting the most sensitive parameters at different time scales is followed to calibrate/validate the DIPDSG model blocks for: 1) flow rate; 2) pollutants (carbon, nitrogen); 3) temperature; and, 4) transport. Simulation results show that the model successfully describes daily/weekly and seasonal variations and the effect of rainfall and snow melting on the influent flow rate, pollutant concentrations and temperature profiles. Furthermore, additional phenomena such as size and accumulation/flush of particulates of/in the upstream catchment and sewer system are incorporated in the simulated time series. Finally, this study is complemented with: 1) the generation of additional future scenarios showing the effects of different rainfall patterns (climate change) or influent biodegradability (process uncertainty) on the generated time series; 2) a demonstration of how to reduce the cost/workload of measuring campaigns by filling the gaps due to missing data in the influent profiles; and, 3) a critical discussion of the presented results balancing model structure/calibration procedure complexity and prediction capabilities.