Wastewater treatment and algal production in high rate algal ponds with carbon dioxide addition

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 CO2 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 CO2 addition achieved a mean algal productivity of 16.7 g/m2/d for the HRAP4d (4 d HRT, maximum algae productivity of 24.7 g/m2/d measured in January 08) and 9.0 g/m2/d for the HRAP8d (8 d HRT)). Algae biomass produced in the HRAPs was efficiently harvested by simple gravity settling units (mean harvested algal productivity: 11.5 g/m2/d for the HRAP4d and 7.5 g/m2/d for the HRAP8d respectively). Higher bacterial composition and the larger size of algal/bacterial flocs of the HRAP8d biomass increased harvestability (83%) compared to that of HRAP4d biomass (69%).

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Nutrient removal in wastewater treatment high rate algal ponds with carbon dioxide addition

Water Science & Technology ◽

10.2166/wst.2011.114 ◽

2011 ◽

Vol 63 (8) ◽

pp. 1758-1764 ◽

Cited By ~ 77

Author(s):

J. B. K. Park ◽

R. J. Craggs

Keyword(s):

Nitrogen Removal ◽

Organic Nitrogen ◽

Inorganic Nitrogen ◽

Nitrogen Loss ◽

Bacterial Biomass ◽

Pilot Scale ◽

High Rate ◽

High Rate Algal Ponds ◽

Carbon Dioxide Addition ◽

Co2 Addition

The influence of CO2 addition to high rate algal ponds (HRAPs) on nitrogen removal was investigated using two pilot-scale HRAPs operated with different hydraulic retention times (HRT: 4 and 8 days), and was compared to the nitrogen removal by the 8-day HRT pond before CO2 addition was installed. Nitrogen balances were calculated by partitioning total nitrogen into organic and inorganic nitrogen (NH+4-N and NO−3-N), and by separation of the organic nitrogen into particulate (PON) and dissolved organic nitrogen (DON). PON was further divided into algal organic nitrogen (AON) and bacteria organic nitrogen (BON) to investigate nitrogen mass flow in the HRAPs. This research shows that the proportion of algae in the algal/bacterial biomass in the longer 8-day HRT HRAP8d (55.6%) was appreciably lower than that in the shorter 4-day HRT HRAP4d (80.5%) when CO2 was added to control the maximum pH to <8.0 during the summer. Higher bacterial biomass in the longer 8-day HRT HRAP corresponded with higher nitrification rates, indicating that the longer 8-day HRT in the summer was detrimental for two reasons: lower algal productivity and increased nitrogen loss through nitrification/denitrification. Overall nitrogen removal of ~60% in the HRAPs with CO2 addition was mainly achieved by algal assimilation followed by sedimentation in the settling unit.

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Algal production in wastewater treatment high rate algal ponds for potential biofuel use

Water Science & Technology ◽

10.2166/wst.2011.200 ◽

2011 ◽

Vol 63 (10) ◽

pp. 2403-2410 ◽

Cited By ~ 55

Author(s):

J. B. K. Park ◽

R. J. Craggs

Keyword(s):

Wastewater Treatment ◽

Biomass Production ◽

Total Lipid ◽

Lipid Content ◽

Algal Biomass ◽

Bacterial Biomass ◽

Total Lipid Content ◽

High Rate ◽

Algal Production ◽

Co2 Addition

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 HRAPs (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 HRAPE) 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 HRAPs 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 HRAPE (15.2 g/m2/d) was improved by CO2 addition by ∼30% compared with that of the control HRAPW (10.6 g/m2/d). Total lipid content of the biomass grown on both HRAPs was slightly reduced (from 25% to 20%) with CO2 addition and the maximum total lipid content of ∼40% was observed in the HRAPW when low NH4+-N concentration (<0.5 mg/L) and high maximum pH (>10.0) occurred. Total lipid content of the biomass increased by ∼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 nitrogenlimiting conditions.

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Algal biofuels from wastewater treatment high rate algal ponds

Water Science & Technology ◽

10.2166/wst.2011.100 ◽

2011 ◽

Vol 63 (4) ◽

pp. 660-665 ◽

Cited By ~ 158

Author(s):

R. J. Craggs ◽

S. Heubeck ◽

T. J. Lundquist ◽

J. R. Benemann

Keyword(s):

Wastewater Treatment ◽

Nutrient Removal ◽

Large Scale ◽

Low Cost ◽

Algal Species ◽

Climatic Conditions ◽

Biofuel Production ◽

High Rate ◽

Algal Production ◽

High Rate Algal Ponds

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 CO2 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.

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A review of potential methods for zooplankton control in wastewater treatment High Rate Algal Ponds and algal production raceways

Algal Research ◽

10.1016/j.algal.2015.06.024 ◽

2015 ◽

Vol 11 ◽

pp. 211-226 ◽

Cited By ~ 59

Author(s):

Valerio Montemezzani ◽

Ian C. Duggan ◽

Ian D. Hogg ◽

Rupert J. Craggs

Keyword(s):

Wastewater Treatment ◽

High Rate ◽

Algal Production ◽

High Rate Algal Ponds ◽

Potential Methods

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Increased pond depth improves algal productivity and nutrient removal in wastewater treatment high rate algal ponds

Water Research ◽

10.1016/j.watres.2014.01.025 ◽

2014 ◽

Vol 53 ◽

pp. 271-281 ◽

Cited By ~ 80

Author(s):

Donna L. Sutherland ◽

Matthew H. Turnbull ◽

Rupert J. Craggs

Keyword(s):

Wastewater Treatment ◽

Nutrient Removal ◽

High Rate ◽

High Rate Algal Ponds ◽

Algal Productivity

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Viability of nematode eggs in high rate algal ponds: the effect of physico-chemical conditions

Water Science & Technology ◽

10.2166/wst.2000.0683 ◽

2000 ◽

Vol 42 (10-11) ◽

pp. 371-374 ◽

Cited By ~ 8

Author(s):

S. Araki ◽

J. M. González ◽

E. de Luis ◽

E. Bécares

Keyword(s):

Hydraulic Retention Time ◽

Pilot Scale ◽

High Rate ◽

Sterile Water ◽

Egg Viability ◽

High Rate Algal Ponds ◽

Helminth Eggs ◽

Physico Chemical ◽

Nematode Eggs ◽

Chemical Conditions

The viability of Parascaris equorum eggs was studied in two experimental pilot-scale high-rate algal ponds (HRAPs) working in parallel with 4 and 10 days hydraulic retention time respectively. Semi-permeable bags of cellulose (15000 daltons pore size) were used to study the effect of physico-chemical conditions on the survival of these helminth eggs. Three thousand eggs were used in each bag. Replicates of these bags were submerged for 4 and 10 days in the HRAPs and egg viability was compared with that in control bags submerged in sterile water. After 4 days exposure, 60% reduction in viability was achieved, reaching 90% after 10 days, much higher than the 16% and 25% found in the control bags for 4 and 10 days respectively. Ionic conditions of the HRAP may have been responsible for up to 50–60% of the egg mortality, suggesting that mortality due to the ionic environment could be more important than physical retention and other potential removal factors.

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