The dairy industry produces significant quantities of wastewater that have a high potential to pollute
the environment if it is not properly treated. Dairy wastewater is rich in organic materials along with
other pollutants, and anaerobic treatment technologies have been successfully applied due to its high
biodegradability. Several research papers have been published on the application of anaerobic biofilm
technologies for dairy wastewater under different operational conditions. This paper provides a critical
review focusing on biofilm reactors for anaerobic treatment of dairy wastewaters of varying strengths.
The effects of organic loading rate and hydraulic retention time on the performance of bioreactors are
discussed and operational problems are summarized. Evaluation of reports indicates that biofilm reactors
have great performance stability and hybrid bioreactors provide higher organic matter removal and
methane production