Nature-based Technologies Research Articles

Effect of wastewater containing mixture of nanoparticles on organic matter removal, power generation, and biofilm integrity in sediment microbial fuel cell

ABSTRACT Industrial wastewaters from the cosmetic industry contain high organic strength and mixture of nanoparticles (NPs). Sediment microbial fuel cell (MFC) is an emerging nature-based technology that can treat complex wastewaters. The aim of this study is to understand the effect of a binary mixture of zinc oxide (ZnO) and copper oxide (CuO) NPs (concentration: 1 + 1 and 10 + 10 mg/L) on the organic matter removal, power generation, and biofilm health of sediment MFCs after a long-term operation of 120 days. The high chemical oxygen demand (COD) removal (>95%) observed for all reactors signified the minimal impact of 10 mg/L NP mixture on treatment. The dissolved organic carbon (DOC) removal from the sediment was reduced by 8% due to NPs. NPs also led to 42.2% higher anode extracellular polymeric substances (EPS) and 46.65% lesser cathode EPS generation. The maximum power density of 0.29 mW/m2 was obtained for the 10 mg/L NP reactor, with the average being 23% higher than the no-NP control reactor. This was the first study to explore the effect of the mixture of NPs on the performance of an MFC. The results indicated that sediment MFCs can sustain high mixture concentrations of NPs. Furthermore, variation of parameters can aid in establishing the feasibility of this technology for treating wastewater with NPs.

Implementation of Decentralized Sanitation Systems with Nature-Based Technologies: Advantages and Challenges in Rural Areas, Slums and Urban Communities

Implementation of Decentralized Sanitation Systems with Nature-Based Technologies: Advantages and Challenges in Rural Areas, Slums and Urban Communities

Treatment of Dairy Farm Runoff in Vegetated Bioretention Systems Amended with Biochar

Nitrogen and fecal indicator bacteria (FIB) in runoff from concentrated animal feeding operations (CAFOs) can impair surface and groundwater quality. Bioretention systems are low impact nature-based technologies that can effectively treat CAFO runoff if modified with an internal water storage zone (IWSZ) or amended with biochar. In this study, the performances of four pilot-scale modified bioretention systems were compared to assess the impacts of (1) amending bioretention media with biochar and (2) planting the systems with Muhlenbergia. The system with both plants and biochar amendment had the best performance, with an average of 5.58 log reduction in E. coli and 98% removal of total nitrogen (TN). All systems treated the first pore volume well as new runoff flushed the treated water from the IWSZ. Biochar improved TN and FIB removal due to its high capacity to adsorb or retain ammonium (NH4+), dissolved organic nitrogen, dissolved organic carbon, and E. coli. Planting improved performance, possibly by increasing rhizosphere microbial activity.

Changes in soil bacterial community structure in a short-term trial with different silicate rock powders

BackgroundThe use of rock powders in soil has emerged as a nature-based technology to improve soil properties relevant to crop development and for atmospheric carbon dioxide removal (CDR) via enhanced rock weathering (ERW). Although modeling this process is crucial, the soil microbiome has been identified as the main reason why several experimental and field results do not fit the geochemical and kinetic theoretical models. Here, the hypothesis that the bacterial community structure is modulated by the application of different silicate rock powders was tested. One phonolite, three basalt variations and one granite, as well as KCl treatments, were applied to a Ferralsol cultivated with Brachiaria in short-term pedogeochemical experiments and assessed after 1 (1M), 4 (4M) and 8 (8M) months.ResultsThe main changes in soil bacterial structure were observed at 8M and found to be modulated according to rock type, with petrochemistry and mineralogy acting as the main drivers. The content of microbial biomass carbon tended to decrease over time in the Control and KCl treatments, especially at 4M, while the rock treatments showed constant behavior. The sampling time and treatment affected the richness and diversity indices. The Si, Ca and Fe from mafic minerals were the main chemical elements related to the soil bacterial changes at 8M.ConclusionsThe type (acidity) of silicate rock powder modulated the soil bacterial community (SBC) in a pot experiment with tropical soil. The specificity of the SBC for each rock type increased with time until the end of the experiment at 8 months (8M). The carbon content in the microbial biomass was lower in the rock powder treatments in the first month (1 M) than in the control and KCl treatments and was equal to or higher than that in the 8 M treatment. This result illustrates the challenge of modeling rock powder dissolution in soil since the soil medium is not inert but changes concurrently with the dissolution of the rock.Graphical

Practice of Low-Cost River Training Works on the Bank of Mohana River in Kailari Rural Municipality, Nepal

Purpose: Kailali, the district that lies in the Far-west of Nepal witness the sever flood and the damage caused by it annually. This study helped us to assess the practice and impact of low-cost River training works in Mohana River of Kailari Rural Municipality to prevent flood control. Design/Methodology/Approach: The study was conducted during the period from March 2022 to May 2023. Field observation, in-depth interview, focus group discussion and questionnaire survey were the major tool applied for the investigation. Findings/Results: The major effect related to river encroachment was land inundation. Further, it was seen that the local people preferred the low-cost river protection works done by utilizing local resources such as bamboo. They believe this technology is easy to execute, cheaper and can be constructed quickly during the time of emergency. During study it was also found that there are government and other non-government agencies supporting to these low-cost techniques for riverbank protections. Originality/Value: The study would like to suggest that the low-cost river protection works should be identified by the government at different level and promote these kinds of nature-based technologies that use local resources. Paper Type: Causal-comparative Research

Assisted phytoextraction as a nature-based solution for the sustainable remediation of metal(loid)-contaminated soils.

Soil contamination is a significant environmental issue that poses a threat to human health and the ecosystems. Conventional remediation techniques, such as excavation and landfilling, are often expensive, disruptive, and unsustainable. As a result, there has been growing interest in developing sustainable remediation strategies that are cost-effective, environmentally friendly, and socially acceptable. One such solution is phytoextraction: a nature-based approach that uses the abilities of hyperaccumulator plants to uptake and accumulate metals and metalloids (potentially toxic elements [PTE]) without signs of toxicity. Once harvested, plant biomass can be treated to reduce its volume and weight by combustion, thus obtaining bioenergy, and the ashes can be used for the recovery of metals or in the construction industry. However, phytoextraction has shown variable effectiveness due to soil conditions and plant species specificity, which has led researchers to develop additional approaches known as assisted phytoextraction to enhance its success. Assisted phytoextraction is a remediation strategy based on modifying certain plant traits or using different materials to increase metal uptake or bioavailability. This review article provides a practical and up-to-date overview of established strategies and the latest scientific advancements in assisted phytoextraction. Our focus is on improving plant performance and optimizing the uptake, tolerance, and accumulation of PTE, as well as the accessibility of these contaminants. While we highlight the advantages of using hyperaccumulator plants for assisted phytoextraction, we also address the challenges and limitations associated with this approach. Factors such as soil pH, nutrient availability, and the presence of other contaminants can affect its efficiency. Furthermore, the real-world challenges of implementing phytoextraction on a large scale are discussed and strategies to modify plant traits for successful phytoremediation are presented. By exploring established strategies and the latest scientific developments in assisted phytoextraction, this review provides valuable guidance for optimizing a sustainable, nature-based technology. Integr Environ Assess Manag 2024;20:2003-2022. © 2024 SETAC.

Nature based solutions for removal of steroid estrogens in wastewater.

Estrogens are a growing problem in wastewater discharges because they are continuously entering the environment and are biologically active at extremely low concentrations. Their effects on wildlife were first identified several decades before, but the environmental limits and the remedial measures are still not completely elucidated. Most conventional treatment processes were not designed with sufficiently long retention times to effectively remove estrogens. Nature-based wastewater treatment technologies such as treatment wetlands (TW) and high-rate algal ponds (HRAP) are economically feasible alternatives for decentralized wastewater treatment and have promise for removing steroid hormones including estrogens. For small communities with populations below 50,000, the overall cost of TWs and HRAPs is considerably lower than that of advanced decentralized treatment technologies such as activated sludge systems (AS) and sequencing batch reactors (SBR). This results from the simplicity of design, use of less materials in construction, lower energy use, operation and maintenance costs, and operation by non-skilled personnel. The nature-based technologies show high removal (>80%) for both natural and synthetic estrogens. Estrogen removal in TWs can be enhanced using alternative media such as palm mulch, biochar, and construction wastes such as bricks, instead of traditional substrates such as sand and gravel. While TWs are effective in estrogen removal, they have the disadvantage of requiring a relatively large footprint, but this can be reduced by using intensified multilayer wetland filters (IMWF). Using filamentous algae in HRAP (high-rate filamentous algal pond; HRFAP) is an emerging technology for wastewater treatment. The algae supply oxygen via photosynthesis and assimilate nutrients into readily harvestable filamentous algal biomass. Diurnal fluctuations in oxygen supply and pH in these systems provide conditions conducive to the breakdown of estrogens and a wide range of other emerging contaminants. The performance of these nature-based systems varies with seasonal changes in environmental conditions (particularly temperature and solar irradiation), however a greater understanding of operating conditions such as loading rate, hydraulic retention time (HRT), pond/bed depth, dissolved oxygen (DO) concentration and pH, which influence the removal mechanisms (biodegradation, sorption and photodegradation) enable TWs and HRAPs to be successfully used for removing estrogens.

Comparison of Vertical and Horizontal Subsurface Constructed Wetland for Water Pollutant Reduction of Brantas River

Improving the water quality of the Brantas River can be achieved by implementing nature-based technology by using the Brantas River as a raw water source for clean water. In this research, subsurface flow constructed wetlands, which include vertical subsurface constructed wetlands (VSSFCWs) and horizontal subsurface constructed wetlands (HSSFCWs), are used as a sustainable and low-cost approach to improve water quality. The VSSFCW system is configured with a layer of gravel substrate, Heliconia psittacorum, and a layer of activated carbon. The configuration for the HSSFCW system is also similar but without the activated carbon layer. This research aimed to determine the quality of the post-treatment water using CWs as an eco-garden to reduce pollutants from the Brantas River. Measurement of water samples from the reactor with laboratory-scale dimensions at the Environmental Laboratory of the State University of Malang, where water samples were taken from the Dam Kadalpang, Brantas River. These measurements were made on physicochemical parameters such as pH, DO, temperature, conductivity, salinity, turbidity, TDS, BOD, and COD. There were four observation points in this research, namely VSSFCW with Heliconia psittacorum and control VSSFCW without plants, where both were given an activated carbon layer, as well as HSSFCW with Heliconia psittacorum and control HSSFCW without plants. The results of data analysis showed that both CWs systems with plants were able to reduce turbidity up to 99% and BOD with a performance efficiency reaching 89%. Both systems also removed COD with a removal efficiency of 73%. TDS was also reduced in both CWs, although there was no significant difference. Similar results were obtained in conductivity and salinity. The pH, temperature, and DO conditions at each observation point met the quality standards and recommendations of previous studies, which became one of the factors supporting the reduction performance of the VSSFCW system. The pollutant degradation capability of the CWs system shows that it can reduce pollutants in the water and it is suitable for use as raw water in the production of clean water.

Decentralized Constructed Wetlands for Wastewater Treatment in Rural and Remote Areas of Semi-arid Regions

Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and to investigate the use of Paulownia trees in VFCWs for wastewater treatment. To compare the efficiency of the plants based on the treatment performance of the VFCWs, three units were prepared and composed of Paulownia, the commonly used Phragmites Australis, and an unplanted unit used as a control during the experimental program. The results show significant reductions in both the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) levels for both planted units, with removal ratios for COD and BOD5 of 60% to 98%, respectively. Both Paulownia and Phragmites Australis significantly reduced the levels of COD and BOD5 in the effluent, with removal percentages ranging from 57.1% to 98% for COD and 49.1% to 98% for BOD5. The control unit, without plantings, showed a lower but still significant removal percentage for both COD (from 55.1% to 96.1%) and BOD5 (from 48.3% to 97.8%). Thus, the results reveal that the efficiency of constructed wetlands can be significantly enhanced by the presence of suitable plant species, such as Paulownia and Phragmites Australis, and constructed wetlands can be a viable and cost-effective option for the treatment of wastewater in various settings, with the added benefit of using the relevant biodiversity.

NATURE BASED INNOVATIONS IN THE DEVELOPMENT OF BIOECONOMY

The main purpose of the article was to present the benefits and challenges related to the bioeconomy as a subsector of the economy, as well as the impact of the biological revolution on the bioeconomy. The market readiness of various nature-based innovations in agriculture was also assessed. The bioeconomy was found to be a right path to sustainable development, addressing social and environmental challenges while supporting economic growth. Thus, it determines a more resilient and resource-efficient development. Nature-based innovations harness the power of natures resilience, efficiency and adaptability to meet societal challenges in a sustainable way. These innovations offer promising economic solutions while increasing the protection of biodiversity and the health of ecosystems. Based on feedback from key stakeholders, the Garther Hype Cycle model was developed. The productivity phase is reached by those technologies and products that have managed to break out of their niche and gain widespread acceptance. In the analysis, this level was achieved by biological control and the use of beneficial microorganisms. Biological control in particular has been identified as a nature-based technology that dominates todays agriculture and will increase in importance in the future.

Climate change effects on denitrification performance of woodchip bioreactors treating agricultural tile drainage

Denitrifying woodchip bioreactors (WBRs) are a nature-based technology that are increasingly used to control nonpoint source nitrate (NO3−) pollution in agricultural catchments. The treatment effectiveness of WBRs depends on temperature and hydraulic retention time (HRT), both of which are affected by climate change. Warmer temperatures will increase microbial denitrification rates, but the extent to which the resulting benefits to treatment performance may be offset by intensified precipitation and shorter HRTs is not clear. Here, we use three years of monitoring data from a WBR in Central New York State to train an integrated hydrologic-biokinetic model describing links among temperature, precipitation, bioreactor discharge, denitrification kinetics, and NO3− removal efficiencies. Effects of climate warming are assessed by first training a stochastic weather generator with eleven years of weather data from our field site, and then adjusting the distribution of precipitation intensities according to the Clausius-Clapeyron relationship between water vapor and temperature. Modeling results indicate, in our system, faster denitrification rates will outweigh the influence of intensified precipitation and discharge under warming, leading to net improvements in NO3− load reductions. Median cumulative NO3− load reductions at our study site from May - October are projected to increase from 21.7% (interquartile range 17.4%–26.1%) under baseline hydro-climate to 41.0% (interquartile range 32.6–47.1%) with a + 4 °C change in mean air temperature. This improved performance under climate warming is driven by strong nonlinear dependence of NO3− removal rates on temperature. Temperature sensitivity may increase with woodchip age and lead to stronger temperature-response in systems like this one with a highly aged woodchip matrix. While the impacts of hydro-climatic change on WBR performance will depend on site-specific properties, this hydrologic-biokinetic modeling approach provides a framework for assessing climate impacts on the effectiveness of WBRs and other denitrifying nature-based systems.

Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions.

Biochar is one of the few nature-based technologies with potential to help achieve net-zero emissions agriculture. Such an outcome would involve the mitigation of greenhouse gas (GHG) emission from agroecosystems and optimization of soil organic carbon sequestration. Interest in biochar application is heightened by its several co-benefits. Several reviews summarized past investigations on biochar, but these reviews mostly included laboratory, greenhouse, and mesocosm experiments. A synthesis of field studies is lacking, especially from a climate change mitigation standpoint. Our objectives are to (1) synthesize advances in field-based studies that have examined the GHG mitigation capacity of soil application of biochar and (2) identify limitations of the technology and research priorities. Field studies, published before 2022, were reviewed. Biochar has variable effects on GHG emissions, ranging from decrease, increase, to no change. Across studies, biochar reduced emissions of nitrous oxide (N2 O) by 18% and methane (CH4 ) by 3% but increased carbon dioxide (CO2 ) by 1.9%. When biochar was combined with N-fertilizer, it reduced CO2 , CH4 , and N2 O emissions in 61%, 64%, and 84% of the observations, and biochar plus other amendments reduced emissions in 78%, 92%, and 85% of the observations, respectively. Biochar has shown potential to reduce GHG emissions from soils, but long-term studies are needed to address discrepancies in emissions and identify best practices (rate, depth, and frequency) of biochar application to agricultural soils.

Performance of hybrid biofilter based on rice husks/sawdust treating grey wastewater.

An innovative nature-based technology for wastewater treatment is the hybrid biofiltration, which combines complex symbiotic relationships between plants, earthworms and microorganisms with adequate support components. This latter could be optimized using organic supports. The aim of this research was to evaluate the performance of hybrid biofilters based on rice husks/sawdust treating grey wastewater from mining camps. Four biofilters using an active layer (rice husks/sawdust: 50/50%, v/v) at 60(B60) and 45(B45) cm height and operating for 64 days at a hydraulic loading rate between 1 and 5 m3/m2d were monitored. Eisenia foetida Savigny and Cyperus papyrus L. were used as a biotic component. COD, N-NH4+, NO3-, NO2-, PO43- and fecal coliforms were weekly monitored. Results showed that the most efficient HB was using 60 cm as an active layer and operating at 3 m3/m2d, which reported average removal efficiencies for COD, NH4+, NO3-, PO43- and fecal coliforms up to 85, 89, 47, 49 and 99.9%, respectively. Organic support improved the rate growth for Cyperus papirus L. and E. foetida Savigny up to 50%. Hybrid biofiltration using organic residues is low-cost, providing all-encompassing operational and performance features, improving the wastewater reclamation opportunities.

Breaking water carbon nexus by the natural biological system: ultimate solution for ESG challenges

Clean water supply has become an enormous challenge in pursuance of the global warming process. Water technologies have traditionally created carbon emissions and chemical reactions that pollute the landscape, aquifers, and the air. The need for carbon footprint reduction and corporate ESG consideration has led to adopt a more environmentally friendly water treatment and management system. The Natural Biological System (NBS) is a nature-based technology for sewage and waste stream treatment and management, rehabilitating affected water bodies, reducing greenhouse gas (GHG) emissions, and rebalancing eco-systems. The NBS is a patent-tailored solution with the ability of large-scale water treatment and a negative carbon footprint promoting the user ESG rating. From Chile to India, the NBS is changing the global water-energy equation, reducing dependence on energy and maintenance, freeing up valuable water resources for on-site usage, and restoring nature's ability to preserve and protect itself and to stop the escalating climate change effects.

Reconciling Nature-Technology-Child Connections: Smart Cities and the Necessity of a New Paradigm of Nature-Sensitive Technologies for Today’s Children

There is a serious and problematic disconnection between children and the natural environment. This has been documented across various disciplines and fields of endeavour, including science, the creative arts, the social sciences, education, design, and the humanities. The nature–people disconnection is particularly concerning at this present juncture when understanding and advocating for the natural environment is necessary to address global environmental crises. Smart cities have, to date, focused on business and economic directions. In recent times, there has been an emerging awareness that such technologically advanced urban environments must link to and inspire an understanding and care for nature in more profound and meaningful ways. Therefore, this paper aims to identify opportunities and discuss how technology can improve this interaction through advancing and implementing nature-positive and nature-sensitive technologies through a critical review of the literature spanning smart cities, children, and nature-based technologies. Such linkages can serve as a driving force behind the transformation of cities as they adapt to support initiatives, such as the post-2020 biodiversity agenda.

Removal of pathogens from greywater using green roofs combined with chlorination

Greywater is an important alternative water resource which could be treated and reused in buildings, reducing the freshwater demand in drought affected areas. For the successful implementation of this solution, it is important to ensure the microbial safety of treated greywater. This study examined the microbiological quality of treated greywater produced by an emergent nature-based technology (green roofs) and a chlorination process. Specifically, the effect of substrate, substrate depth, and vegetation on the removal of total coliforms, Escherichia coli, and enterococci in experimental green roofs treating greywater was examined for a period of about 12 months. In addition, the ability of chlorination to inactivate the abovementioned pathogen indicators was evaluated and their potential regrowth was examined. Results shown that green roofs filled with 10 cm of perlite reduce total coliform concentration by about 0.4 log units while green roofs filled with 20 cm of vermiculite reduce total coliform concentration by about 1.2 log units. In addition, the use of vegetation in green roofs improves the removal of pathogenic bacteria by about 0.5 log units in comparison with unvegetated systems. In all cases, the effluents of green roofs failed to satisfy the criteria for indoor reuse of treated greywater for non-potable uses such as toilet flushing without a disinfection process. The addition of 3 mg/L of chlorine in the effluent provided safe greywater microbiological quality for storage periods of less than 24 h, while longer periods resulted in the significant regrowth of pathogens. In contrast, a chlorination dose of 7 mg/L completely secured inactivation of pathogen indicators for periods of up to 3 days.

Influence of DOM and microbes on Fe biogeochemistry at a riverbank filtration site

Riverbank filtration (RBF) constitutes an important part of the water cycle, which involves active natural filtration leading to pollution of river water being intercepted and retained. The RBF has the function of water purification, but retention of exogenous pollutants in the RBF system complicates biogeochemical processes due to the presence of primary active components. In this study, we verified the essential role of microbial mediation during the interactions between primary Fe minerals in the RBF system and dissolved organic matter (DOM) in river water based on lab-scale experiments. The results demonstrated that DOM from infiltration of river water increased the amount of iron (Fe) released from the sediment in RBF, leading to an increase in Fe concentration in groundwater by higher than one order of magnitude. In particular, the existence of Fe bacteria even made this effect more thorough and more complex. Abiotic reduction was shown to play a more significant role in increasing Fe release than microbe-mediated reduction. Increasing the amount of Fe released could change the distribution of Fe minerals at the sediment surface, thereby affecting the structure of the microbial community in the RBF system and decreasing the DOM concentration in the groundwater. Moreover, As and Mn were found to behave in a similar manner as Fe due to their close biochemical properties when interacting with primary minerals in sediment. This study not only provides mechanistic insight into the higher Fe concentrations encountered in the groundwater of nearby rivers but also has important practical implications for developing nature-based technologies for water pollution control and environmental remediation.

Characterization of unconventional sand-based substrates for adsorption of micropollutants in nature-based systems.

The focus of this study is the characterization of unconventional sand-based substrates used in our previous project EmiSûre, (Interreg Greater Region (German federal states Rhineland-Palatinate and Saarland, the Grand Duchy of Luxembourg, regions Wallonia and Lorraine from Belgium and France, respectively), 2017-2021). The project aimed to develop and test alternative, nature-based technologies for the elimination of micropollutants (MPs) from municipal wastewater. For the characterization, two approaches were chosen. In the first approach, adsorption kinetics with a single compound allowed a perception of the adsorption capacity of the studied substrates compared to conventional substrates (granular activated carbons). This knowledge was completed by the second approach: an implementation of the studied substrates in packed-bed columns, which treated a mixture of 27MPs in tap water for 10 months. Additionally, all three substrates (bentonite sand, sand with 15% activated biochar and sand with 15% zeolite) were characterized for physical and chemical properties, and the microbial potential of the activated and non-activated biochar was examined. From the studies, it is clear that the sand with an admixture of activated biochar is the most efficient sorbent in terms of single compound adsorption in batch (dye) and adsorption of 27MPs on packed-bed columns. In contrast to the two other substrates, it shows long-term stable removal efficiencies. In the packed-bed columns, 18 out of 27 compounds were removed on average with high efficiency (80-99%), which is impressive, if we consider the variety of the compounds examined (pharmaceuticals, herbicides, pesticides, etc.) and their removal in conventional treatments. Additionally, adsorption models were created for the experimental data of all compounds adsorbed on the substrate with an admixture of activated biochar resulting in the best fit with the combined Langmuir-Freundlich model. These satisfying results suggest the application of the sand-based substrate with an admixture of activated biochar for further research and possibly upscale installations with the aim to offer and prove a reasonable and efficient alternative for MPs elimination from municipal wastewater.

Economic Assessment of Energy Consumption in Wastewater Treatment Plants: Applicability of Alternative Nature-Based Technologies in Portugal

Understanding how to address today’s global challenges is critical to improving corporate performance in terms of economic and environmental sustainability. In wastewater treatment systems, such an approach implies integrating efficient treatment technologies with aspects of the circular economy. In this business field, energy costs represent a large share of operating costs. This work discusses technological and management aspects leading to greater energy savings in Portuguese wastewater treatment companies. A mixed methodology, involving qualitative and quantitative aspects, for collecting and analysing data from wastewater treatment plants was used. The qualitative aspects consisted of a narrative analysis of the information available on reports and websites for 11 wastewater management companies in Portugal (e.g., technologies, treated wastewater volumes and operating costs) followed by a review of several international studies. The quantitative approach involved calculating the specific energy consumption (kWh/m3), energy operating costs (EUR/m3) and energy operating costs per population equivalent (EUR/inhabitants) using data from the literature and from Portuguese companies collected from the SABI database. The results suggested that the most environmentally and economically sustainable solution is algae-based technology which might allow a reduction in energy operating costs between 0.05–0.41 EUR/m3 and 15.4–180.8 EUR/inhabitants compared to activated sludge and other conventional methods. This technology, in addition to being financially advantageous, provides the ability to eliminate the carbon footprint and the valorisation of algae biomass, suggesting that this biotechnology is starting to position itself as a mandatory future solution in the wastewater treatment sector.

Advancing the Sponge City Agenda: Evaluation of 22 plant species across a broad range of life forms for stormwater management

In 2012, China introduced the Sponge City Agenda as a solution to challenges such as increasing urbanisation and population growth, leading to urban flooding and water pollution. The initiative requires new nature-based technologies tailored for Chinese conditions. Biofiltration or bioretention systems have proven to be promising technologies to mitigate stormwater pollution. Plant selection form a key component of system design. However, to date plant selection research has been limited, largely focusing on Australian native species monitored under a limited number of wetting and drying patterns. To address this gap, a large scale laboratory study was undertaken to test the hydraulic and treatment performance of 22 plant species, native to or common to Jiangsu Province, China, over a period of 15 months under varying frequency of inflows (corresponding to 3, 15 and 22 antecedent dry days). A wide variation in system infiltration capacity (up to 8-fold), nitrogen removal (up to 5-fold during wet conditions and up to 10-fold during dry conditions, between 20% and 80%) and phosphorus removal (up to 2-fold, between 35% and 95%) was found across plant species. In regards to heavy metals, plant-related contributions were observed for Cd, Ni and Zn removal (up to 90% removal overall). Overall, this study shows that while plants are not universally effective, a range of plant species, across a broad range of life forms, encompassing flowering herbs, reeds, shrubs, grasses, sedges, climbing plants and trees, can be used for effective stormwater treatment in China and elsewhere. It points to plant morphological and physiological characteristics being more important parameters and suggest future work investigate the relationship between plant evapotranspiration, water dynamics (incl. Antecedent drying), root traits and pollutant removal to advance the sustainable use of plants for stormwater treatment.