Thermophilic anaerobic digester with ultrafilter for solids stabilization

Area of Science:

• Environmental Engineering
• Biotechnology
• Waste Management

Background:

• Thermophilic anaerobic digestion with ultrafiltration (TADU) offers benefits like enhanced solids destruction and pathogen removal.
• Potential challenges include ultrafilter fouling, reduced flux, and high volatile fatty acid (VFA) concentrations.

Purpose of the Study:

• To evaluate the long-term performance of a thermophilic anaerobic digester coupled with a sintered titanium cross-flow ultrafilter for dairy manure treatment.
• To assess key parameters including volatile solids (VS) destruction, VFA levels, pathogen removal, and ultrafilter flux maintenance.

Main Methods:

• A thermophilic anaerobic digester was operated for over five months with dairy manure at a hydraulic retention time (HRT) of 23 days.
• A sintered titanium, cross-flow ultrafilter was used for solids separation.
• Ultrafilter cleaning involved sequential application of caustic (3.5% NaOH), water, and acid (3% phosphoric acid).

Main Results:

• The system achieved an average VS destruction of 49% with a low filtrate VFA concentration of 220 mg/L as HAc.
• Effluent fecal coliform concentration averaged 10(2) MPN/100 mL, indicating significant pathogen reduction.
• Ultrafilter fluxes of 40-80 L/m2-hr were sustained through regular chemical cleaning cycles.

Conclusions:

• The TADU system demonstrates effective VS destruction and pathogen removal from dairy manure.
• Chemical cleaning protocols successfully maintained ultrafilter flux, mitigating fouling issues.
• The low pathogen counts in treated biosolids suggest potential for reuse as livestock bedding, provided sand bedding is replaced to prevent equipment damage.