In general, aerobic systems are suitable for the treatment of low strength wastewaters, biodegradable COD concentrations less than 1,000 mg/L, while anaerobic systems are suitable for the treatment of high strength wastewaters and biodegradable COD concentrations over 4,000 mg/L.

Article Combined anaerobic-aerobic and UV/H2O2 processes for the tre...

Dear Nimantha,

Since the late 1970's we develop, design and realize high-rate anaerobic digestion (HRAD) plants worldwide on a broad range of effluents. Over 80% of these HRAD plants are based on UASB to convert soluble organics (COD) to methane at up to 99% efficiency depending on the influent composition after adequate equalization and conditioning. When influent COD is lower than about 5000 mg/l then the COD conversion efficiency drops due the residual recalcitrant COD in the HRAD effluent.

Dear Nimantha,

Yes, there is likely to be a direct relationship between UASB performance and COD loading.  At low volumetric COD loading the performance of the system will not change much with small changes in volumetric loading.  At high volumetric loading, small changes in volumetric loading can have a large effect on performance.  The definitions of "low" and "high" loading will depend on the characteristics of your treatment system and on the characteristics of your wastewater.  I would expect soft drink and ice cream wastewater to be quite biodegradable, so a UASB should be able to accept a relatively high volumetric loading and produce acceptable results.  Effective load equalization will be critical.  Proper management of cleaning solution waste (which can be very difficult to treat) will also be critical.

Nimantha

COD of the effluent directly affect the treatment efficiency of not only UASB but any kind of a biological treatment system.As a rule of thumb when increasing the COD of the effluent treatment efficiency gradually decreases.

Dear K V V,

I'm sorry to respectfully disagree with your rule of thumb.

At the SAME COD load (kg/d) and operating conditions (pH, temperature, nutrients, ...) the COD removal efficiency will INCREASE when the COD inlet concentration increases in any biological treatment as proven in practice and by model based simulations.

This is happen normally during the startup period but in mature stage efficiency decreases when increasing the COD of influent.I mean removal efficiency as a % over the cod of influent. This could be varied according to the different environmental condition

many effort were dun in  this field but until now i did not seed any successes.