AlgaEurope 2026 · Malta | Track 07 of 11
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AlgaEurope 2026 › Track #07
SESSION TRACK · #07 OF 11 · ENVIRONMENTAL ENGINEERING

Wastewater Treatment
& CO₂ Sequestration

Microalgae are the only organisms that simultaneously remove nitrogen, phosphorus, and heavy metals from water while converting CO₂ into biomass. This dual function — wastewater polishing plus carbon capture — sits at the core of circular economy industrial design.

Carbon Capture Dec 8–11 · Hilton Malta N/P Remediation · Circular Economy
95%
NH₄⁺ removal in HRAPs — peak performance (Sutherland 2014)
1.83 kg CO₂/kg DW
Net CO₂ fixed per kg algal biomass produced
€0.5–1.5/m³
Wastewater polishing cost — algae vs activated sludge (€1.8–3.2)
15% flue gas
Max CO₂ concentration tolerated by most green algae without pH crash
500 ha
HRAP target area to treat full Wellington (NZ) municipal load — NovAlgae pilot data
Process Architecture
Algal Wastewater Treatment + CO₂ Capture: Integrated Flow
FLUE GAS / CO₂ Industrial source 5–15% CO₂ HIGH-RATE ALGAL POND Municipal / industrial WW CO₂ + N + P → biomass HRT 4–8 days · 0.3 g/L/d HARVESTING Centrifugation / DAF ~10–20 g/L slurry BIOREFINERY Pigments → protein → lipid ANAEROBIC DIGESTION Biogas + digestate (fertiliser) Polished effluent (NH₄⁺ <2 mg/L) CARBON CREDIT 1.83 kg CO₂/kg biomass ISO 14064-2 verified → ETS market value

High-Rate Algal Ponds (HRAPs) use paddle-wheel mixing to maintain turbulence. Treated effluent exits at BOD <10 mg/L, TSS <30 mg/L, NH₄⁺ <2 mg/L — meeting EU Urban Wastewater Directive discharge standards. Coupled with biorefinery, the system converts a cost centre (wastewater treatment) into a revenue-positive operation via biomass products + carbon credits.

Nutrient Removal
N and P Removal Rates — Algal Systems vs Activated Sludge

Nitrogen and phosphorus are regulated under EU Urban Wastewater Treatment Directive (91/271/EEC, revised 2022). Microalgae remove N and P biologically without chemical precipitation — a significant advantage because chemical dosing (alum, FeCl₃) generates sludge with no recovery pathway. All values from Sutherland et al. (2014, Water Research 53:268–281) HRAP trials and Razzak et al. (2013, Renewable & Sustainable Energy Reviews) review.

NH₄⁺-N Removal (%)
HRAP (outdoor, summer)
95%
PBR (controlled)
88%
Activated sludge (AS)
80%
HRAP (outdoor, winter)
65%
PO₄³⁻-P Removal (%)
HRAP (outdoor, summer)
92%
PBR (controlled)
83%
Chemical (alum dosed)
96% (sludge)
Activated sludge
45%
Landmark Achievements
Industrial-Scale Proofs of Concept
2010
Masdar Algae Biofuel & Wastewater Project — Abu Dhabi. The first large-scale demonstration of algae treating industrial wastewater from desalination plants while producing biomass for biofuel. 2,000 m² outdoor raceway ponds, treating 500 m³/day of effluent, achieved 90%+ N removal. Published learnings on pond design at hyperarid conditions directly shaped EU HRAP research protocols (Craggs et al., 2012).
2014
Sutherland et al. (NIWA, NZ) — HRAP N Removal at Municipal Scale. Landmark outdoor HRAP trial treating real municipal wastewater at 1 ha pilot in Christchurch, NZ. Achieved 95% NH₄⁺ removal in summer, 65% in winter. Published Water Research 53:268–281. Became the primary field reference for EU algal wastewater research. Established seasonal correction models adopted in H2020 AlgaeCampus and PROSSESS projects.
2022
NovAlgae (Portugal) — 500 m² HRAP at Leiritratos Dairy Treatment Facility. First commercial deployment of algal wastewater treatment at a Portuguese dairy: Scenedesmus obliquus HRAP removing >85% of N and P from 200 m³/day dairy effluent. Biomass sold as liquid biofertiliser at €120/t. Operational cost 40% below conventional AS treatment. Funded under Portugal 2020 / FEDER. Case study published by Leitão et al. (2023, Bioresource Technology 379:128923).
4BlueTech Focus
Direct CO₂ Capture to Microalgae: 4BlueTech Malta Pilot Design

Mission-critical to 4BlueTech

4BlueTech's industrial CO₂ capture technology uses microalgae as the biological sink. The Malta pilot (2025–2027) targets 500 kg CO₂/day absorbed into Nannochloropsis oceanica cultures coupled to a 200 kW gas turbine flue stream. Target biomass output: 250 kg DW/day → feed-grade omega-3 ingredient after disruption. Net carbon balance: −1.1 kg CO₂eq per kg biomass DW under ISO 14044 system boundary.

CO₂ Tolerance Engineering

Wild-type strains tolerate <5% CO₂ before pH collapse. Strain adaptation via serial transfer at elevated CO₂ (Kodama et al., 1993) produces strains tolerant to 15–20% CO₂, directly matching industrial flue gas. Patent: Bhola et al. (2011) WO2011119491A1 — microalgae adapted to high-CO₂ environments for biofuel production. 4BlueTech pilot uses proprietary adapted Nannochloropsis line tolerant to 14% CO₂.

EU Carbon Market Value

EU ETS carbon price averaged €63/t CO₂ in 2023 (EEX data). At 500 kg CO₂/day, the 4BlueTech Malta unit earns €11.50/day in ETS credit equivalence (verified under voluntary carbon standard). This revenue stream partially offsets pond CAPEX, reducing the effective payback from 7.2 years to 5.8 years in the base-case financial model. Bioproduct revenue from biomass (omega-3 feed) adds a further €85/day at target production.

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