The present work aims to study the removal of color and COD from livestock wastewater by electrocoagulation (EC) process using Al electrodes. The Box-Behnken design and response surface methodology were used to investigate the effects of major operating variables and optimization conditions. The predicted values of responses obtained using the response function agree well with the experimental data. Economical operating conditions and removal efficiencies were found to be pH of 8, current density of 30 mA/cm 2 , electrolysis time of 30 min and NaCl concentration of 1 g/L, and 95.2 % (Y 1 ) and 93% (Y 2 ), respectively.

>> This paper describes the reduction of a hydrogen sulfide (H2S) generated from a biogas plant. Micro bubble system is adopted to supply air into the water in the reaction chamber, which can increase the contact area of the supplied air to the reserving water. Two stage reaction chambers having two reaction rooms are designed and manufactured to enhance the reduction rate of a hydrogen sulfide. Sodium hydroxide (NaOH) is also considered to get rid of a hydrogen sulfide. Air volume rate to the water in a reaction chamber is maintained between 0.5 and 1.0m 3 /min. Throughout experimental measurement of the concentration of a hydrogen sulfide by changing the volume of supplied air into the water, reduction rate of a hydrogen sulfide increases as air volume increases. Adding sodium hydroxide to the water with the air supply can reduce effectively a hydrogen sulfide up to 99.5% from biogas. It is noted that a hydrogen sulfide generated by a biogas plant can reduce by supplying micro bubble air and sodium hydroxide effectively.