(87c) Anaerobic Treatment of High Strength Industrial Wastes By Moving Bed Bioreactors (MBBR)

Somnath Basu
Headworks International
11000 Brittmoore Park Drive, Houston, TX 77014
sbasu@headworksintl.com

ABSTRACT
Effluents from many industrial processes contain high concentrations of organic wastes (COD). These include petrochemical, food & beverage, and breweries & distilleries among others. Treatment of high COD wastes pose major challenges to the operating cost and environment traditional aerobic activated sludge process due to their:
a) high energy cost of aeration as every kilogram of COD requires one kilogram of oxygen; and
b) high cost of transportation and disposal of residual solids resulting from biochemical reactions.
These two activities constitute the largest operating cost of a wastewater treatment plant.
Anaerobic processes are net energy positive and sustainable for high strength waste treatment compared to their aerobic counterpart as:
a) they do not consume any energy for aeration as these processes take place in absence of air;
b) very low generation of residual biosolids requiring much lower hauling and disposal costs.
On the other hand, anaerobic processes produce biogas that can be utilized as a source of energy for heating, steam and power generation on-site. From energy viewpoint, the production far outweighs the consumption to maintain the bioreactor well mixed by agitators and at 35 to 38 C. Thus, anaerobic processes are sustainable as biogas is a source of ‘Green Energy’.
Despite these advantages, anaerobic treatment faces a significant operating challenge in solid-liquid-gas separation can be challenging because:
a) trapped gas impedes solids settling
b) waste sludge does not flocculate well
This difficulty leads to occasional washout of biomass from the reactor. Restart and stabilization of reactor can be time consuming and can affect the smooth operation of production processes.
An anaerobic MBBR reactor overcomes this constraint as the biomass in the reactor is attached to media surfaces while the media themselves are freely suspended and uniformly distributed within the reactor. Other advantages of this type of reactor configurations, as listed below.
• Robustness against toxic or shock loads;
• Resiliency to peak flows and loads; and
• Easy recovery from washout situations as attached growth provides an inventory of biomass
This paper will present the fundamentals of anaerobic MBBR as a sustainable process for high strength waste treatment with the results of a case study of a pilot scale brewery wastewater treatment.