When is bioaugmentation appropriate and what factors determine success?

Bioaugmentation - adding specialized microorganisms to enhance degradation - is appropriate when: indigenous populations are insufficient or lack required degradation capabilities, rapid treatment is needed, or specific contaminants require specialized pathways. Success factors: 1) Organism selection - must have proven degradation capability, survive environmental conditions, compete with native microflora. 2) Site conditions - pH, temperature, oxygen, nutrients must support introduced organisms; toxic conditions may inhibit. 3) Contaminant bioavailability - organisms can only degrade accessible compounds; sorbed or NAPL-phase contaminants may limit efficacy. 4) Competition and predation - native microbes, protozoa may outcompete or consume added organisms. 5) Delivery and distribution - ensure organisms reach contamination; inoculation density typically 10^6-10^9 cells/mL. 6) Monitoring - track organism survival and activity, not just addition. Often more successful in controlled bioreactor systems than in situ. Bioaugmentation for chlorinated solvents (Dehalococcoides) has shown field success.