Microalgae for municipal wastewater nutrient remediation: mechanisms, reactors and outlook for tertiary treatment

This review explores the use of microalgae for nutrient removal in municipal wastewater treatment, considering recent improvements in the understanding of removal mechanisms and developments of both suspended and non-suspended systems. Nutrient removal is associated to both direct and indirect uptake, with the former associated to the biomass concentration and growth environment (reactor). Importantly, direct uptake is influenced by the Nitrogen:Phosphorus content in both the cells and the surrounding wastewater, with opposite trends observed for N and P. Comparison of suspended and non-suspended systems revealed that whilst all were capable of achieving high levels of nutrient removal, only non-suspended immobilized systems could do so with reduced hydraulic retention times of less than 1 day. As microalgae are photosynthetic organisms, the metabolic processes associated with nutrient assimilation are driven by light. Optimization of light delivery remains a key area of development with examples of improved mixing in suspended systems and the use of pulsating lights to enhance light utilization and reduce costs. Recent data provide increased confidence in the use of microalgae for nutrient removal in municipal wastewater treatment, enabling effluent discharges below 1 mg L−1 to be met whilst generating added value in terms of bioproducts for energy production or nutrient recovery. Ultimately, the review suggests that future research should focus on non-suspended systems and the determination of the added value potential. In so doing, it is predicted that microalgae systems will be significant in the delivery of the circular economy

Guidelines for measuring and reporting environmental parameters for experiments in greenhouses

Background: The importance of appropriate, accurate measurement and reporting of environmental parameters in plant sciences is a significant aspect of quality assurance for all researchers and their research. There is a clear need for ensuring research across the world can be compared, understood and where necessary replicated by fellow researchers. A common set of guidelines to educate, assist and encourage comparativeness is of great importance. On the other hand, the level of effort and attention to detail by an individual researcher should be commensurate with the particular research being conducted. For example, a researcher focusing on interactions of light and temperature should measure all relevant parameters and report a measurement summary that includes sufficient detail allowing for replication. Such detail may be less relevant when the impact of environmental parameters on plant growth and development is not the main research focus. However, it should be noted that the environmental experience of a plant during production can have significant impact when subsequent experiments investigate plants at a molecular, biochemical or genetic level or where species interactions are considered. Thus, researchers are encouraged to make a critical assessment of what parameters are of primary importance in their research and these parameters should be measured and reported. Content: This paper brings together a collection of parameters that the authors, as members of International Committee on Controlled Environment Guidelines (ICCEG) in consultation with members of our three parent organizations, believe constitute those which should be recorded and reported when publishing scientific data from experiments in greenhouses. It provides recommendations to end users on when, how and where these parameters should be measured along with the appropriate internationally standardized units that should be used

Can houseplants improve indoor air quality by removing CO2 and increasing relative humidity?

High indoor CO2 concentrations and low relative humidity (RH) create an array of well-documented human health issues. Therefore, assessing houseplants’ potential as a low-cost approach to CO2 removal and increasing RH is important. We investigated how environmental factors such as ’dry’ ( 0.30 m3 m-3) growing substrates, and indoor light levels (‘low’ 10 µmol m-2 s-1, ‘high’ 50 µmol m-2 s-1 and ‘very high’ 300 µmol m-2 s-1), influence the plants’ net CO2 assimilation (‘A’) and water-vapour loss. Seven common houseplant taxa – representing a variety of leaf types, metabolisms and sizes – were studied for their ability to assimilate CO2 across a range of indoor light levels. Additionally, to assess the plants’ potential contribution to RH increase, the plants’ evapo-transpiration (ET) was measured. At typical ‘low’ indoor light levels ‘A’ rates were generally low (< 3.9 mg hr-1). Differences between ‘dry’ and ’wet’ plants at typical indoor light levels were negligible in terms of room-level impact. Light compensation points (i.e. light levels at which plants have positive ‘A’) were in the typical indoor light range (1-50 µmol m-2 s-1) only for two studied Spathiphyllum wallisii cultivars and Hedera helix; these plants would thus provide the best CO2 removal indoors. Additionally, increasing indoor light levels to 300 µmol m-2 s-1 would, in most species, significantly increase their potential to assimilate CO2. Species which assimilated the most CO2 also contributed most to increasing RH

Simulating the integration of photovoltaic technology on the modern infantry soldier using modelling andsimulation:scenarios and guidelines

The operational range and manoeuvrability of the modern infantry soldier is restricted by the overall load and bulk of equipment ranging from 50 to 75 kg. Today’s soldiers rely heavily on batteries to meet their power requirements, which make up 25% of the overall load. This results in a significant increase on soldier’s physical stress and cognitive burden. Recent developments in renewable energy, and more particularly the evolution of very thin and flexible wearable photovoltaic devices, provide promising solutions for the application of such technologies on the infantry soldier. However, since these flexible substrate devices are still under development or produced at a very small scale, their application and use has to be simulated prior to integrating to the infantry soldier. Such simulations need to take into account the specific requirements and different fields of operation of the infantry soldier, in the context of weather, date and time, global location and for different military mission environments. This paper presents a number of simulations performed for a wide range of scenarios in the context of the Solar Soldier project. It discusses the key results, offering a set of guidelines for the positioning and integration of such renewable energy technology on the modern infantry soldier. Moreover, this paper suggests future improvements on the methodology and optimisation of the procedures