Optimization of dairy waste water treatment process using combined experimental and mathematical modelling approach

Abstract

In this study, combined experimental and mathematical modelling approach is developed to optimize diary waste water treatment plant. Anaerobic digestion model no.l (ADM1) was built in a simulator called Aquasim 2.1f. UASB model comprises of three CSTR (continuous stirred tank reactor) compartmenis as sludge bed, blanket and settler. Experiments were conducted at waste water treatment plant (WWTP) under three volumetric flow rates i.e. 10 m3/d, 15 m3/d and 25 m3/d. Plant is being operated at 25 m3/d. Three parameters such as cumulative biogas volume, pH and COD were measured. At the operating volumetric flow rate, WWTP was simulated with the new model and parameters such as VFA, gas composition, inhibition and biomass growth rates were obtained. By varying recycle ratio from sludge bed to blanket and settler to blanket, appropriate recycle ratio was obtained to get best fitted model, (bed to blanket - 0.8 and settler to blanket 0.6). Optimization was performed under two scenarios .i.e. by varying volumetric flow rates and input COD level. It was found that above 30 m3/d UASB become unstable producing 21% of CH4 and 75% of CO2. Also it was found that 7500 mgCOD/1 can be treated at the volumetric rate of 30 m3/d without any instability to existing WWTP.