While research and development of algal biofuels are currently receiving much interest and funding, they are still not commercially viable at today’s fossil fuel prices. However, a niche opportunity ...may exist where algae are grown as a by-product of high rate algal ponds (HRAPs) operated for wastewater treatment. In addition to significantly better economics, algal biofuel production from wastewater treatment HRAPs has a much smaller environmental footprint compared to commercial algal production HRAPs which consume freshwater and fertilisers. In this paper the critical parameters that limit algal cultivation, production and harvest are reviewed and practical options that may enhance the net harvestable algal production from wastewater treatment HRAPs including CO
2 addition, species control, control of grazers and parasites and bioflocculation are discussed.
This paper investigates the effect of recycling on biomass energy yield in High Rate Algal Ponds (HRAPs). Two 8 m3 pilot-scale HRAPs treating primary settled sewage were operated in parallel and ...monitored over a 2-year period. Volatile suspended solids were measured from both HRAPs and their gravity settlers to determine biomass productivity and harvest efficiency. The energy content of the biomass was also measured. Multiplying biomass productivity and harvest efficiency gives the ‘harvestable biomass productivity’ and multiplying this by the energy content defines the actual ‘biomass energy yield’. In Year 1, algal recycling was implemented in one of the ponds (HRAPr) and improved harvestable biomass productivity by 58% compared with the control (HRAPc) without recycling (HRAPr: 9.2 g/m2/d; HRAPc: 5.8 g/m2/d). The energy content of the biomass grown in HRAPr, which was dominated by Pediastrun boryanum, was 25% higher than the control HRAPc which contained a mixed culture of 4–5 different algae (HRAPr: 21.5 kJ/g; HRAPc: 18.6 kJ/g). In Year 2, HRAPc was then seeded with the biomass harvested from the P. boryanum dominated HRAPr. This had the effect of shifting algal dominance from 89% Dictyosphaerium sp. (which is poorly-settleable) to over 90% P. boryanum in 5 months. Operation of this pond was then switched to recycling its own harvested biomass, which maintained P. boryanum dominance for the rest of Year 2. This result confirms, for the first time in the literature, that species control is possible for similarly sized co-occurring algal colonies in outdoor HRAP by algal recycling. With regard to the overall improvement in biomass energy yield, which is a critical parameter in the context of algal cultivation for biofuels, the combined improvements that recycling triggered in biomass productivity, harvest efficiency and energy content enhanced the harvested biomass energy yield by 66% (HRAPr: 195 kJ/m2/day; HRAPc: 118 kJ/m2/day).
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•Algal species control was possible in wastewater treatment HRAP by algal recycling.•Algal recycling improved harvestable biomass productivity and energy yield.•Higher productivity, harvestability and energy content increased energy yield.
This paper investigates the influence of recycling gravity harvested algae on species dominance and harvest efficiency in wastewater treatment High Rate Algal Ponds (HRAP). Two identical pilot-scale ...HRAPs were operated over one year either with (HRAP
r) or without (HRAP
c) harvested algal biomass recycling. Algae were harvested from the HRAP effluent in algal settling cones (ASCs) and harvest efficiency was compared to settlability in Imhoff cones five times a week. A microscopic image analysis technique was developed to determine relative algal dominance based on biovolume and was conducted once a month. Recycling of harvested algal biomass back to the HRAP
r maintained the dominance of a single readily settleable algal species (
Pediastrum sp.) at >90% over one year (compared to the control with only 53%). Increased dominance of
Pediastrum sp. greatly improved the efficiency of algal harvest (annual average of >85% harvest for the HRAP
r compared with ∼60% for the control). Imhoff cone experiments demonstrated that algal settleability was influenced by both the dominance of
Pediastrum sp. and the species composition of remaining algae. Algal biomass recycling increased the average size of
Pediastrum sp. colonies by 13–30% by increasing mean cell residence time. These results indicate that recycling gravity harvested algae could be a simple and effective operational strategy to maintain the dominance of readily settleable algal species, and enhance algal harvest by gravity sedimentation.
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► Algal recycling increased dominance of a settleable alga,
Pediastrum sp. in HRAP. ► Increased dominance of
Pediastrum sp. greatly improved gravity algal harvest. ► Algal recycling increased the average size and biovolume of
Pediastrum colonies. ► Algal recycling increased the mean cell residence time of
Pediastrum colonies.
This paper examines the potential of algae biofuel production in conjunction with wastewater treatment. Current technology for algal wastewater treatment uses facultative ponds, however, these ponds ...have low productivity (∼10 tonnes/ha.y), are not amenable to cultivating single algal species, require chemical flocculation or other expensive processes for algal harvest, and do not provide consistent nutrient removal. Shallow, paddlewheel-mixed high rate algal ponds (HRAPs) have much higher productivities (∼30 tonnes/ha.y) and promote bioflocculation settling which may provide low-cost algal harvest. Moreover, HRAP algae are carbon-limited and daytime addition of CO(2) has, under suitable climatic conditions, the potential to double production (to ∼60 tonnes/ha.y), improve bioflocculation algal harvest, and enhance wastewater nutrient removal. Algae biofuels (e.g. biogas, ethanol, biodiesel and crude bio-oil), could be produced from the algae harvested from wastewater HRAPs, The wastewater treatment function would cover the capital and operation costs of algal production, with biofuel and recovered nutrient fertilizer being by-products. Greenhouse gas abatement results from both the production of the biofuels and the savings in energy consumption compared to electromechanical treatment processes. However, to achieve these benefits, further research is required, particularly the large-scale demonstration of wastewater treatment HRAP algal production and harvest.
It has previously been shown that recycling gravity harvested algae promotes Pediastrum boryanum dominance and improves harvestability and biomass production in pilot-scale High Rate Algal Ponds ...(HRAPs) treating domestic wastewater. In order to confirm the reproducibility of these findings and investigate the mechanisms responsible, this study utilized twelve 20 L outdoor HRAP mesocosms operated with and without algal recycling. It then compared the recycling of separated solid and liquid components of the harvested biomass against un-separated biomass. The work confirmed that algal recycling promoted P. boryanum dominance, improved 1 h-settleability by >20% and increased biomass productivity by >25% compared with controls that had no recycling. With regard to the improved harvestability, of particular interest was that recycling the liquid fraction alone caused a similar improvement in settleability as recycling the solid fraction. This may be due to the presence of extracellular polymeric substances in the liquid fraction. While there are many possible mechanisms that could account for the increased productivity with algal recycling, all but two were systematically eliminated: (i) the mean cell residence time was extended thereby increasing the algal concentration and more fully utilizing the incident sunlight and, (ii) the relative proportions of algal growth stages (which have different specific growth rates) was changed, resulting in a net increase in the overall growth rate of the culture.
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•Algal species control was possible in wastewater treatment HRAP by recycling.•Recycling improved productivity, settleability and Pediastrum boryanum dominance.•Recycling extended MCRT, increasing algal concentration and fully utilizing incident sunlight.•Recycling shifted the relative proportion of algae in the different life-cycle stages.•This resulted in a net increase in the overall growth rate of the pond culture.
There is increasing scrutiny from healthcare organizations towards the utility and associated costs of imaging. MRI has traditionally been used as a high‐end modality, and although shown extremely ...important for many types of clinical scenarios, it has been suggested as too expensive by some. This editorial will try and explain how value should be addressed and gives some insights and practical examples of how value of MRI can be increased. It requires a global effort to increase accessibility, value for money, and impact on patient management. We hope this editorial sheds some light and gives some indications of where the field may wish to address some of its research to proactively demonstrate the value of MRI.
Level of Evidence: 5
Technical Efficacy: Stage 5
J. Magn. Reson. Imaging 2019;49:e14–e25.
Wastewater treatment High Rate Algal Ponds with CO2 addition could provide cost-effective and efficient tertiary-level wastewater treatment with the co-benefit of algal biomass production for biofuel ...use. Wastewater grown algal biomass can have a lipid content of 10-30% of dry weight, which could be used to make biodiesel. This research investigated algal biomass and total lipid production by two pilot-scale wastewater treatment HRAP(S) (4-day HRT) with and without CO2 addition under New Zealand mid summer (Nov-Jan) conditions. The influence of CO2 addition on wastewater treatment performance was also determined. CO2 was added to one of the HRAPs (the HRAP(E)) by maintaining the maximum pH of the pond below 8. Measurements of HRAP influent and effluent water qualities, total lipid content and algal biomass production were made twice a week over the experimental period. Both HRAP(S) achieved high levels of organic compound and nutrient removal, with >85% SBOD5, >92 NH4(+)-N and >70% DRP removal. Algal/bacterial biomass production in the HRAP(E) (15.2 g/m2/d) was improved by CO2 addition by approximately 30% compared with that of the control HRAP(W) (10.6 g/m2/d). Total lipid content of the biomass grown on both HRAP(S) was slightly reduced (from 25% to 20%) with CO2 addition and the maximum total lipid content of approximately 40% was observed in the HRAP(W) when low NH4(+)-N concentration (<0.5 mg/L) and high maximum pH (>10.0) occurred. Total lipid content of the biomass increased by approximately 15% under nitrogen limiting conditions, however, overall algal/bacterial biomass production was reduced by half during the period of nitrogen limitation. More research is required to maintain algal production under near nitrogen-limiting conditions.
Pan-bromodomain and extra terminal domain (BET) inhibitors interact equipotently with the eight bromodomains of the BET family of proteins and have shown profound efficacy in a number of in vitro ...phenotypic assays and in vivo pre-clinical models in inflammation or oncology. A number of these inhibitors have progressed to the clinic where pharmacology-driven adverse events have been reported. To better understand the contribution of each domain to their efficacy and improve their safety profile, selective inhibitors are required. This article discloses the profile of GSK046, also known as iBET-BD2, a highly selective inhibitor of the second bromodomains of the BET proteins that has undergone extensive pre-clinical in vitro and in vivo characterization.
High rate algal ponds (HRAPs) provide improved wastewater treatment over conventional wastewater stabilisation ponds; however, algal production and recovery of wastewater nutrients as algal biomass ...is limited by the low carbon:nitrogen ratio of wastewater. This paper investigates the influence of CO(2) addition (to augment daytime carbon availability) on wastewater treatment performance and algal production of two pilot-scale HRAPs operated with different hydraulic retention times (4 and 8 days) over a New Zealand Summer (November-March, 07/08). Weekly measurements were made of influent and effluent flow rate and water qualities, algal and bacterial biomass production, and the percentage of algae biomass harvested in gravity settling units. This research shows that the wastewater treatment HRAPs with CO(2) addition achieved a mean algal productivity of 16.7 g/m(2)/d for the HRAP(4d) (4 d HRT, maximum algae productivity of 24.7 g/m(2)/d measured in January 08) and 9.0 g/m(2)/d for the HRAP(8d) (8 d HRT)). Algae biomass produced in the HRAPs was efficiently harvested by simple gravity settling units (mean harvested algal productivity: 11.5 g/m(2)/d for the HRAP(4d) and 7.5 g/m(2)/d for the HRAP(8d) respectively). Higher bacterial composition and the larger size of algal/bacterial flocs of the HRAP(8d) biomass increased harvestability (83%) compared to that of HRAP(4d) biomass (69%).
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