What are the Applications of Bioelectrochemical Systems in ETP Plants?

As effluent treatment plants strive for energy neutrality and resource recovery, bioelectrochemical systems (BES) are emerging as innovative solutions for transitioning wastewater from waste to resource streams. BES use electroactive microbes,catalysing oxidation-reduction reactions at electrodes to achieve water treatment objectives coupled with energy/resource harvesting. We will explores the applications of BES that effluent treatment plants can adopt for enhanced sustainability.

Overview of Bioelectrochemical Systems in Effluent Treatment Plants

BES combine principles from biochemistry and electrochemistry to extract value from organic waste streams using specialised bacteria that transfer electrons extracellularly during anaerobic respiration. This enables electricity generation via microbial fuel cells (MFCs) or microbial electrolysis cells (MECs), which drive electrochemical transformations without adding chemical oxidants.

Key BES configurations include:

Microbial Fuel Cells (MFCs): Bioelectrogenic bacteria oxidise organics at the anode, releasing electrons captured as currents and reducing oxygen at the cathode.

Microbial Electrolysis Cells (MECs): Apply a small external voltage reversing natural reaction driving hydrogen gas evolution or reductive dechlorination. 

Microbial Desalination Cells (MDCs): Utilize bioelectronic oxidation, driving transmembrane salt removal without high pressures.

Wastewater Treatment Applications

Carbon Removal: 

Anode-respiring bacteria break down organic carbon in wastewater while transferring electrons and generating electricity, offsetting plant energy demands.

Nitrogen Removal:

Electrobiological denitrification removes nitrates from effluents as nitrogen gas coupled to electricity generation in biocathode configurations. 

Desalination:

MDCs and microbial-ion exchange combine wastewater treatment with energy-efficient saline water treatment.

Toxic Removal:

BES enable reductive decontamination of recalcitrant dyes, chlorinated solvents, and heavy metals without chemical dosing.

Resource/Energy Recovery Possibilities

Using bioelectrochemical mechanisms provides unique opportunities:

Nutrients Recovery:

Struvite (magnesium ammonium phosphate) precipitation at cathodes enables nutrient capture as fertilisers.

Bioplastics Production:

Recovered electrons drive biosynthesis of polyhydroxyalkanoates - a biodegradable plastic from waste. 

Hydrogen Gas:

Applying voltage for water electrolysis in MECs enables simultaneous organics oxidation and hydrogen evolution as biofuel.

Bioelectrochemical Mining: 

Metal recovery from effluents by reductive precipitation at biocathodes forming value-added products.

Integration at Effluent Treatment Plants 

BES modules can be incorporated at various locations in plant configurations:

Mainstream: 

Integrated within activated sludge tanks or anaerobic digesters to enhance organics and nutrient removal.

Side-stream: 

Dedicated BES units treating high-strength centre/side streams from dewatering processes.

Polishing:

Tertiary treatment of secondary effluents in BES cells removing residual contaminants pre-discharge.

Co-digestion:

BES processing food wastes and sludges together improves bioenergy/biochemical recovery.

With advantages like minimal sludge production, operational flexibility, and effluent quality, facilities can simultaneously meet treatment standards and resource recovery objectives.

Economic & Environmental Benefits

Key economic drivers making BES compelling include:

Net Energy Production:

Electricity directly generates offsets of up to 50% of treatment plant demands, saving costs.

Water Reuse Enablement:

High-quality effluents from BES allow greater recycling, reducing freshwater demands.

Resource Recovery Revenue:

The sale of value-added biochemicals, nutrients or fuels like hydrogen improves project economics. 

Reduced Life-cycle Impacts:

Owing to passive treatment without aeration/chemical consumption, BES have lower carbon/environmental footprints.Government incentives around energy neutrality, resource circularity and innovations also improve payback periods.

Overcoming Implementation Challenges

Despite benefits, key challenges constraining mainstream adoption exist:

System Scale-up:

Difficulties in scaling up basic BES cell designs to handle larger volumes profitably.

Electrode Costs:

Need for cost-effective, corrosion-resistant electrode materials enabling consistent biofilms and performance.

Microbiology Control:

Maintaining pure cultures that robustly transfer electrons while resisting contamination remains complex.

Organic Loading Rates:

Sustaining reliably high levels of power densities across fluctuations in influent organic concentrations.

Research spanning electrochemical engineering advancements, microbiological understanding, and cost reductions is bridging viability gaps and overcoming implementation barriers.

Conclusion

Using the unique capabilities of electroactive microbes through bioelectrochemical systems provides wastewater treatment facilities with opportunities to enhance their sustainability. By integrating BES innovations spanning microbial fuel cells, microbial electrolysis cells, and microbial desalination cells, plants can simultaneously achieve effluent treatment objectives while recovering value-added resources like bioplastics, nutrients, and hydrogen, along with generating electricity to offset energy needs. While implementation challenges remain, accelerating advancements around scale-up, electrode materials, and microbiological controls promise to transition facilities towards energy-neutral circular resource recovery infrastructure in the future.

To explore customised commercial RO plants, Industrial RO plants, ETP or STP solutions for your needs in your areas and nearby regions, contact Netsol Water at:

Phone: +91-965-060-8473, Email: enquiry@netsolwater.com