Abstract

The feasibility of anaerobic digestion of dairy wastewater at 10°C was investigated in a high height : diameter ratio EGSB reactor. Stable performance was observed at an applied organic loading rate (OLR) of 0.5–2 kg COD m−3 d−1 with chemical oxygen demand (COD) removal efficiencies above 85%. When applied OLR increased to values above 2 kg COD m−3 d−1, biotreatment efficiency deteriorated, with methanogenesis being the rate-limiting step. The bioreactor recovered quickly (3 days) after reduction of the OLR. qPCR results showed a reduction in the abundance of hydrogenotrophic methanogenic Methanomicrobiales and Methanobacteriales throughout the steady state period followed by a sharp increase in their numbers (111-fold) after the load shock. Specific methanogenic activity and maximum substrate utilising rate (A max) of the biomass at the end of trial indicated increased activity and preference towards hydrogenotrophic methanogenesis, which correlated well with the increased abundance of hydrogenotrophic methanogens. Acetoclastic Methanosaeta spp. remained at stable levels throughout the trial. However, increased apparent half-saturation constant (K m) at the end of the trial indicated a decrease in the specific substrate affinity for acetate of the sludge, suggesting that Methanosaeta spp., which have high substrate affinity, started to be outcompeted in the reactor.

Highlights

  • During the last decades, there has been an increased concern with the environment and the limited energy sources available

  • After the organic loading rate (OLR) increased to 4.1 kg chemical oxygen demand (COD) m−3 d−1, during PV, the COD removal efficiency (RE) suddenly dropped to 48% and Volatile Fatty Acids (VFA) concentrations peaked at >770 mg COD L−1

  • VFAs accounted for 76% of the COD present in the effluent, again indicating that methanogenesis was ratelimiting at a higher OLR

Read more

Summary

Introduction

There has been an increased concern with the environment and the limited energy sources available. In this context, ways to treat wastewaters with energy saving methods need to be developed. The application of low-temperature anaerobic digestion (LTAD) at temperatures of 12∘C to 15∘C has been studied at laboratory- and pilot-scale granular sludge-based bioreactors [1,2,3]. Up to date there are only few reports describing LTAD of complex (with the presence of particulate compounds) or low-strength recalcitrant industrial waste streams [4, 5]. The potential for low-strength anaerobic digestion of complex industrial wastewaters at 10∘C remains largely unexplored

Objectives
Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call