FEATURES
ASIA PACIFIC FOOD INDUSTRY november/december 2011
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percent. Finally, the produced biogas from the UASB reactor and the CSTR will be piped out and burned at the flare. Results: • Extreme low surplus sludge production after digestion of FOG and surplus sludge in the CSTR process • Low operating cost due to combination of UASB process with aerobic process Wastewater characteristics Flow t-COD load FOG TSS Temperature System features Buffer tank DAF unit Biothane UASB Extended Aeration Biobulk CSTR Biogas flare
500 m3/d 5,000 kg/d 2,000 mg/l 2,000 mg/l < 40°C 250 m3 21 m3/h 660 m3 1250 m3 500 m3 75 m3/h
Aerobic Wastewater Treatment Aerobic wastewater treatment converts the organic pollutants (COD, BOD) in wastewater into
A granular biomass bucket
a fair amount of excess sludge, and oxidises the rest with oxygen to carbon dioxide. Furthermore, the priority pollutants nitrogen and phosphorus can be effectively removed. However, the operating costs for aeration, sludge treatment and disposal are high so that, whenever feasible, anaerobic treatment systems are preferred. On the other hand, when certain ( s u r f a c e w a t e r ) d i s c h a rg e standards have to be met, the aerobic process will always be needed as a complementary p o l i s h i n g t re a t m e n t s t e p . Furthermore, the aerobic process step can treat wastewaters for which anaerobic treatment is not suited. Moving Bed Biofilm Reactor The MBBR (Moving Bed Biofilm Reactor) is a biological reactor using attached growth bacteria.
CSTR & Aerobic Process
Using less energy and less water results in lower pollution and less stress on ecosystems and water resources, preserving the balance for future generations. The bacteria grow on carriers free flowing in the aeration tank. Nutrients are added to the reactor to guarantee the right level of nitrogen and phosphorous for bacterial development. Aeration is done using blower and aeration piping. A system of sieves is implemented in the aeration tank to retain the carriers within the biological tank. The technology brings a few advantages compared to the common biological treatment, that is the conventional activated sludge or Sequencing Batch Reactor (SBR). Indeed, the MBBR reactor is more compact because the attached bacteria are more active and more concentrated. MBBR is more flexible as the capacity can be easily increased by adding more carriers in the aeration tank. The treatment capacity of the MBBR depends on the filling ratio. The filling with carrier can vary from 10 to 67 percent of the reactor total volume. It is also more resistant to toxic pollution and chemicals, as well as hydraulic and load peaks. Towards A Culture Of Responsibility Industrial wastewater has intrinsic value and it is important t o i m p l e m e n t a p p ro p r i a t e solutions to meet the needs of manufacturers and especially