Brewery Wastewater Management
Brewery Wastewater Treatment
Each brewery generates wastewater with a unique quality, quantity, and seasonal variation pattern. Identification of an appropriate wastewater treatment technology or multiple technologies is strongly influenced by the characteristics of the wastewater stream and the degree of treatment needed to meet site-specific discharge requirements, which itself will depend on whether it is discharged into the public sewer network, into a natural waterway, or whether it is to be reused in the process, or to irrigate the vineyard. The key drivers in choosing a wastewater treatment system are minimizing capital costs, minimize operating costs and making the system as automated and robust as possible, thereby minimizing management requirements.
Physical treatment is for removing coarse solids and other large materials, rather than dissolved pollutants. It may be a passive process, such as sedimentation to allow suspended pollutants to settle out or float to the top naturally. Other typical physical treatments include flow equalization, screening, and grit removal. Physical treatment is necessary to enhance the operation and efficiency of subsequent treatment steps.
Typically, the wastewater is first screened to remove glass, labels, and bottle caps, floating plastic items and spent grains. Manual bar screens may be adequate to smaller breweries; however, mechanical screens are normally used for much larger operations.
After the wastewater has been screened, it may flow into a grit chamber where sand, grit, and small stones settle to the bottom.
Flow equalization is a technique used to consolidate wastewater effluent in holding tanks for “equalizing” before introducing wastewater into downstream brewery treatment processes or for that matter directly into the municipal sewage system.
With the screening completed and the grit removed, wastewater still contains dissolved organic and inorganic constituents along with suspended solids. The suspended solids consist of minute particles of matter that can be removed from the wastewater with further treatment such as sedimentation or chemical flocculation.
Dissolved Air Flotation
Dissolved air flotation (DAF) is an alternative to conventional gravity sedimentation as a way in treating brewery wastewater effluent. The DAF is a liquid-solid separation process in which microscopic air bubbles become attached to solids and then transported to the surface to form a floating blanket. Here a slowly rotating arm skims the top layer of thickened sludge.
Chemical treatment processes involve pH adjustment or coagulation/flocculation by adding different chemicals to the effluent to alter its chemistry. The neutralizing chemicals must be injected into the tanks and mixed adequately for the reactions to take place quickly. Under-mixing or poor injection systems waste chemicals and result in out-of-compliance situations.
Coagulation-flocculation is the first treatment step in the chemical wastewater treatment method. Flocculation is the stirring or agitation of chemically-treated (e.g., aluminum sulfate) water to induce coagulation. Flocculation involves stirring/agitation of chemically-treated effluent to induce coagulation that improves sedimentation performance by increasing particle size, thereby increasing settling efficiency.
Federal law, 40 CFR Sec. 403.5(3) (2), requires that the pH of the wastewater stream be adjusted to greater than 5.0 prior to discharge into the municipal sewer system. There is no mandated upper pH limit, but municipal POTW’s generally set an upper limit of no more than pH 11.5. Many smaller municipalities set their own more restrictive ranges (e.g., pH 6.0–9.0) based on the capacity of their treatment systems.
After the brewery wastewater has undergone physical and chemical treatments, the wastewater can then undergo an additional biological treatment. Biological treatment of wastewater can be either aerobic (with air/oxygen supply) or anaerobic (without oxygen), which are discussed in more detail in the following sections. Generally, aerobic treatment has been applied for the treatment of brewery wastewater and recently anaerobic systems have become an attractive option.
Aerobic Wastewater Treatment
Aerobic wastewater treatment systems include the addition of air (oxygen) within the wastewater reactor. Aerobic wastewater treatment encourages the growth of naturally-occurring aerobic microorganisms as a means of renovating wastewater. Such microbes are the engines of wastewater treatment plants. These systems are effective in reducing BOD/COD to very low levels.
Anaerobic Wastewater Treatment
Anaerobic wastewater treatment processes use bacteria to breakdown BOD, COD, and other organic contaminants with the absence of oxygen. Anaerobic systems do not require the addition of air to the reactors, which lowers energy costs to operate the system. In many instances, anaerobic digestion systems can be energy positive.
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