Brewery Wastewater Management
Anaerobic Wastewater Treatment
Anaerobic wastewater treatment is the biological treatment of wastewater without the use of air or elemental oxygen. Anaerobic treatment is characterized by biological conversion of organic compounds by anaerobic microorganisms into biogas which can be used as a fuel—mainly methane 55 to 75 vol percent and carbon dioxide 25 to 40 vol percent with traces of hydrogen sulfide (Briggs et al., 2004).
Low-Rate Anaerobic Option
A conceptual low-rate anaerobic process for a large brewery may consist of a lined, covered reactor lagoon constructed of native or imported earth fill. The reactor would have an influent and effluent distribution system and mixers; supernatant recycling and sludge systems; process instrumentation and controls; a compressed air system; biogas handling system, including an enclosed biogas flare with flame arrestor; a high-density polyethylene (HDPE) liner with leak monitoring and collection capabilities to protect groundwater (any leakage that accrues is pumped back into the reactor); and a flexible, insulated geomembrane cover.
High-Rate Anaerobic Option
A conceptual high-rate anaerobic system for a large brewery may consist of covered concrete reactors or tanks that treat brewery wastewater biologically at a relatively high rate using what is known as a high-rate anaerobic reactor. High-rate anaerobic reactors include the anaerobic fluidized bed reactor (AFBR), the anaerobic sludge blanket reactor (UASB), and the anaerobic sequencing batch reactor (ASBR).
Anaerobic Fluidized Bed Reactor
In an anaerobic fluidized bed reactor (AFBR), wastewater flows in through the bottom of the reactor, and up through a media (usually sand or activated carbon) that is colonized by active bacterial biomass. The media provides a growth area for the biofilm. This media is “fluidized” by the upward flow of wastewater into the vessel, with the lowest density particles (those with highest biomass) moving to the top.
Anaerobic Sludge Blanket Reactor
In the anaerobic sludge blanket reactor (UASB), the wastewater flows in an upward mode through a dense bed of anaerobic sludge (Figure 25.3). This sludge is mostly of a granular nature (1‒4 mm) having superior settling characteristics (>50 m/hr). The organic materials in solution are attacked by the microbes, which release biogas. The biogas rises, carrying some of the granular microbial blanket.
Biogas Handling and Energy Recovery
A by-product of anaerobic digestion of brewery wastewater is biogas containing methane. Biogas can be captured and recovered for potential reuse as a supplemental fuel source for the brewery, or if necessary, used to power hot water heaters/exchangers that raise the temperature of wastewater entering the anaerobic reactor(s) to optimize the treatment process.
Advantages and Disadvantages
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