Thomas Schaubroeck

Aggregate Size and Architecture Determine Microbial Activity Balance for One-Stage Partial Nitritation and Anammox

ABSTRACT Aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB) cooperate in partial nitritation/anammox systems to remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about granulation so far. In this study, three suspended-growth oxygen-limited autotrophic nitrification-denitrification (OLAND) reactors with different inoculation and operation (mixing and aeration) conditions, designated reactors A, B, and C, were used. The test objectives were (i) to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes and (ii) to relate aggregate morphology, size distribution, and architecture putatively to the inoculation and operation of the three reactors. A nitrite accumulation rate ratio (NARR) was defined as the net aerobic nitrite production rate divided by the anoxic nitrite consumption rate. The smallest reactor A, B, and C aggregates were nitrite sources (NARR, >1.7). Large reactor A and C aggregates were granules capable of autonomous nitrogen removal (NARR, 0.6 to 1.1) with internal AnAOB zones surrounded by an AerAOB rim. Around 50% of the autotrophic space in these granules consisted of AerAOB- and AnAOB-specific extracellular polymeric substances. Large reactor B aggregates were thin film-like nitrite sinks (NARR, <0.5) in which AnAOB were not shielded by an AerAOB layer. Voids and channels occupied 13 to 17% of the anoxic zone of AnAOB-rich aggregates (reactors B and C). The hypothesized granulation pathways include granule replication by division and budding and are driven by growth and/or decay based on species-specific physiology and by hydrodynamic shear and mixing.

Accounting for land use in life cycle assessment: The value of NPP as a proxy indicator to assess land use impacts on ecosystems.

Terrestrial land and its resources are finite, though, for economic and socio-cultural needs of humans, these natural resources are further exploited. It highlights the need to quantify the impact humans possibly have on the environment due to occupation and transformation of land. As a starting point of this paper (1(st) objective), the land use activities, which may be mainly socio-culturally or economically oriented, are identified in addition to the natural land-based processes and stocks and funds that can be altered due to land use. To quantify the possible impact anthropogenic land use can have on the natural environment, linked to a certain product or service, life cycle assessment (LCA) is a tool commonly used. During the last decades, many indicators are developed within the LCA framework in an attempt to evaluate certain environmental impacts of land use. A second objective of this study is to briefly review these indicators and to categorize them according to whether they assess a change in the asset of natural resources for production and consumption or a disturbance of certain ecosystem processes, i.e. ecosystem health. Based on these findings, two enhanced proxy indicators are proposed (3(rd) objective). Both indicators use net primary production (NPP) loss (potential NPP in the absence of humans minus remaining NPP after land use) as a relevant proxy to primarily assess the impact of land use on ecosystem health. As there are two approaches to account for the natural and productive value of the NPP remaining after land use, namely the Human Appropriation of NPP (HANPP) and hemeroby (or naturalness) concepts, two indicators are introduced and the advantages and limitations compared to state-of-the-art NPP-based land use indicators are discussed. Exergy-based spatially differentiated characterization factors (CFs) are calculated for several types of land use (e.g., pasture land, urban land).

Quantifying the Environmental Impact of an Integrated Human/ Industrial-Natural System Using Life Cycle Assessment; A Case Study on a Forest and Wood Processing Chain

Life Cycle Assessment (LCA) is a tool to assess the environmental sustainability of a product; it quantifies the environmental impact of a products life cycle. In conventional LCAs, the boundaries of a products life cycle are limited to the human/industrial system, the technosphere. Ecosystems, which provide resources to and take up emissions from the technosphere, are not included in those boundaries. However, similar to the technosphere, ecosystems also have an impact on their (surrounding) environment through their resource usage (e.g., nutrients) and emissions (e.g., CH4). We therefore propose a LCA framework to assess the impact of integrated Techno-Ecological Systems (TES), comprising relevant ecosystems and the technosphere. In our framework, ecosystems are accounted for in the same manner as technosphere compartments. Also, the remediating effect of uptake of pollutants, an ecosystem service, is considered. A case study was performed on a TES of sawn timber production encompassing wood growth in an intensively managed forest ecosystem and further industrial processing. Results show that the managed forest accounted for almost all resource usage and biodiversity loss through land occupation but also for a remediating effect on human health, mostly via capture of airborne fine particles. These findings illustrate the potential relevance of including ecosystems in the products life cycle of a LCA, though further research is needed to better quantify the environmental impact of TES.

Successful hydraulic strategies to start up OLAND sequencing batch reactors at lab scale

Oxygen‐limited autotrophic nitrification/denitrification (OLAND) is a one‐stage combination of partial nitritation and anammox, which can have a challenging process start‐up. In this study, start‐up strategies were tested for sequencing batch reactors (SBR), varying hydraulic parameters, i.e. volumetric exchange ratio (VER) and feeding regime, and salinity. Two sequential tests with two parallel SBR were performed, and stable removal rates > 0.4 g N l−1 day−1 with minimal nitrite and nitrate accumulation were considered a successful start‐up. SBR A and B were operated at 50% VER with 3 g NaCl l−1 in the influent, and the influent was fed over 8% and 82% of the cycle time respectively. SBR B started up in 24 days, but SBR A achieved no start‐up in 39 days. SBR C and D were fed over 65% of the cycle time at 25% VER, and salt was added only to the influent of SBR D (5 g NaCl l−1). Start‐up of both SBR C and D was successful in 9 and 32 days respectively. Reactor D developed a higher proportion of small aggregates (0.10–0.25 mm), with a high nitritation to anammox rate ratio, likely the cause of the observed nitrite accumulation. The latter was overcome by temporarily including an anoxic period at the end of the reaction phase. All systems achieved granulation and similar biomass‐specific nitrogen removal rates (141–220 mg N g−1 VSS day−1). FISH revealed a close juxtapositioning of aerobic and anoxic ammonium‐oxidizing bacteria (AerAOB and AnAOB), also in small aggregates. DGGE showed that AerAOB communities had a lower evenness than Planctomycetes communities. A higher richness of the latter seemed to be correlated with better reactor performance. Overall, the fast start‐up of SBR B, C and D suggests that stable hydraulic conditions are beneficial for OLAND while increased salinity at the tested levels is not needed for good reactor performance.

Quantification of spatially differentiated resource footprints for products and services through a macro-economic and thermodynamic approach

Although natural resources form the basis of our economy, they are not always used in a sustainable way. To achieve a more sustainable economic growth, resource consumption needs to be measured. Therefore, resource footprint frameworks (RFF) are being developed. To easily provide results, these RFF integrate inventory methodologies, at macrolevel mostly input-output (IO) models, with resource accounting methodologies, of which the Ecological Footprint is probably the best known one. The objective of this work is the development of a new RFF, in which a world IO-model (Exiobase), providing a global perspective, is integrated with the CEENE methodology (Cumulative Exergy Extraction from the Natural Environment), offering a more complete resource range: fossil fuels, metals, minerals, nuclear resources, water resources, land resources, abiotic renewable resources, and atmospheric resources. This RFF, called IO-CEENE, allows one to calculate resource footprints for products or services consumed in different countries as the exergy extracted from nature. The way the framework is constructed makes it possible to show which resources and countries contribute to the total footprint. This was illustrated by a case study, presenting the benefits of the frameworks worldwide perspective. Additionally, a software file is provided to easily calculate results.

Correction to Multilayered Modeling of Particulate Matter Removal by a Growing Forest over Time, From Plant Surface Deposition to Washoff via Rainfall

Airborne fine particulate matter (PM) is responsible for the most severe health effects induced by air pollution in Europe. Vegetation, and forests in particular, can play a role in mitigating this pollution since they have a large surface area to filter PM out of the air. Many studies have solely focused on dry deposition of PM onto the tree surface, but deposited PM can be resuspended to the air or may be washed off by precipitation dripping from the plants to the soil. It is only the latter process that represents a net-removal from the atmosphere. To quantify this removal all these processes should be accounted for, which is the case in our modeling framework. Practically, a multilayered PM removal model for forest canopies is developed. In addition, the framework has been integrated into an existing forest growth model in order to account for changes in PM removal efficiency during forest growth. A case study was performed on a Scots pine stand in Belgium (Europe), resulting for 2010 in a dry deposit...

Environmental impact of non-certified versus certified (ASC) intensive Pangasius aquaculture in Vietnam, a comparison based on a statistically supported LCA

Pangasius production in Vietnam is widely known as a success story in aquaculture, the fastest growing global food system because of its tremendous expansion by volume, value and the number of international markets to which Pangasius has been exported in recent years. While certification schemes are becoming significant features of international fish trade and marketing, an increasing number of Pangasius producers have followed at least one of the certification schemes recognised by international markets to incorporate environmental and social sustainability practices in aquaculture, typically the Pangasius Aquaculture Dialogue (PAD) scheme certified by the Aquaculture Stewardship Council (ASC). An assessment of the environmental benefit of applying certification schemes on Pangasius production, however, is still needed. This article compared the environmental impact of ASC-certified versus non-ASC certified intensive Pangasius aquaculture, using a statistically supported LCA. We focused on both resource-related (water, land and total resources) and emissions-related (global warming, acidification, freshwater and marine eutrophication) categories. The ASC certification scheme was shown to be a good approach for determining adequate environmental sustainability, especially concerning emissions-related categories, in Pangasius production. However, the non-ASC certified farms, due to the large spread, the impact (e.g., water resources and freshwater eutrophication) was possibly lower for a certain farm. However, this result was not generally prominent. Further improvements in intensive Pangasius production to inspire certification schemes are proposed, e.g., making the implementation of certification schemes more affordable, well-oriented and facilitated; reducing consumed feed amounts and of the incorporated share in fishmeal, especially domestic fishmeal, etc. However, their implementation should be vetted with key stakeholders to assess their feasibility.

Re-evaluating Primary Biotic Resource Use for Marine Biomass Production: A New Calculation Framework

The environmental impacts of biomass harvesting can be quantified through the amount of net primary production required to produce one unit of harvested biomass (SPPR-specific primary production required). This paper presents a new calculation framework that explicitly takes into account full food web complexity and shows that the resulting SPPR for toothed whales in the Icelandic marine ecosystem is 2.8 times higher than the existing approach based on food web simplification. In addition, we show that our new framework can be coupled to food web modeling to examine how uncertainty on ecological data and processes can be accounted for while estimating SPPR. This approach reveals that an increase in the degree of heterotrophy by flagellates from 0% to 100% results in a two-fold increase in SPPR estimates in the Barents Sea. It also shows that the estimated SPPR is between 3.9 (herring) and 5.0 (capelin) times higher than that estimated when adopting food chain theory. SPPR resulting from our new approach is only valid for the given time period for which the food web is modeled and cannot be used to infer changes in SPPR when the food web is altered by changes in human exploitation or environmental changes.

Mainstream partial nitritation/anammox: balancing overall sustainability with energy savings

Implementation of one-stage nitritation/anammox (i.e. deammonification) for the treatment of sludge digestates allowed net energy positive operation in the wastewater treatment plant (WWTP) in Strass (Austria). To further optimize the overall energy efficiency a first trial to expand the deammonification process to the full-plant wastewater treatment system was performed. The effluent quality, greenhouse gas emissions, energy balance and overall CO2 footprint before and after implementation of mainstream DEMON® were evaluated in this study after one year of operation. In the effluent, a shift from nitrate over nitrite ratios of 31 to ratios of 2 was observed. The higher nitrite levels caused higher N2O emissions up to 2.3% of the N load in the B-stage, increasing the overall greenhouse gas emission of the plant significantly. For the present situation with mainstream DEMON, 11% of the electricity demand in the B-stage could be saved allowing higher net energy productions. These higher energy recoveries could not totally counteract the increased N2O emissions, resulting in a higher CO2 footprint of 36 kg CO2-eq PE−1 year−1 compared to 7 kg CO2-eq PE−1 year−1 before mainstream DEMON. Further optimization of the operational conditions in the mainstream will reveal if higher energy savings can be obtained at lower N2O emissions. First hints towards this can be given based on experimental trials carried out for this study.

Towards a general sustainability assessment of human/industrial and nature-based solutions

To address sustainability issues, a spectrum of human/industrial and nature-based solutions exists, and solutions are often a mix of both, e.g., agriculture uses human/industrial products/services but is based on natural biomass growth. More relevant than defining to what extent a solution is nature-based, is to assess its sustainability, which is argued to align with an increase in human well-being (Schaubroeck and Rugani in J Ind Ecol 21:1464–1477, 2017). Approaches exist to assess the sustainability of nature-based solutions (through ecosystem service assessment) and human/industrial solutions (through life cycle sustainability assessment), but there is a lack of a general sustainability assessment approach that assesses the impact of both natural and human/industrial elements. Such an approach would be applicable to any type of solution, including mixed solutions, such as agriculture. Given the interconnectedness of mankind and the earth (including the industry/economy) and the need to cover future human well-being, this general approach should ideally encompass the integrated modelling of the earth and its support of human well-being. The conventional methodologies of tools (e.g., ecosystem service assessment) would then be embedded into such a modelling approach to provide a general sustainability assessment tool.