Chapter 24

Winery Wastewater Treatment

Biological Treatment: Aerobic Systems in the Winery

Aerobic treatment (introducing oxygen to the effluent) is often used for low BOD effluents or in conjunction with anaerobic systems for treatment prior to use for irrigation. Aerobic systems can be designed for low or high rates of throughput, ranging from low-rate aerated tanks or open ponds, to high-rate membrane bioreactors (MBRs) and moving bed biofilm reactors (MBBRs).

Septic Tanks

For small wineries with low production and wastewater flows, installation of a relatively simple wastewater treatment system consisting of a settling tank (a septic tank) and with a subsurface drainage discharge area (a leach field) may meet their needs (Figure 25.1). In these systems, solids are allowed to settle in the septic tank, and the effluent is discharged to an adjacent leach field. The septic tank provides an anaerobic environment where some nitrogen transformations occur and microbes assimilate and decompose organic material. When the effluent is discharged to the soil, aerobic processes consume remaining BOD and convert much of the wastewater nitrogen to nitrate-N.

Ponds

Ponds are often used by smaller wineries to accomplish biological stabilization (Figure 25.2). The ponds provide an environment for aerobic degradation of wastewater constituents near the surface, coupled with anaerobic degradation by microbes at depth. The basic reaction that occurs in ponds is removal and biological stabilization of residual organic matter by aerobic bacteria that grow in the ponds and remain in suspension.

Pond Microbiology

Clarification processes are used to separate suspended solids from wastewaters. Sedimentation is the most common process, although DAF is also being used where space is a consideration or where solids are easier to float (e.g., anaerobic biosolids). Some wineries have used centrifuges for removing organic solids such as seeds, stems, and skins from wastewater and suspended solids.

Aeration

Aerobic degradation can be accelerated by installing aerators to increase available oxygen and preclude stagnation. Aerated ponds, if properly designed, constructed and managed, can reduce organic, nutrient, and solids loadings and provide good quality effluent fit for irrigation.

Hydraulic Detention Time

Detention times must be long enough for bacteria to reproduce and metabolize the maximum organic waste load entering the pond.

Location and Design

Ponds may be installed where the slope of the land is not too steep to cause problems with their construction and where soils are sufficiently impermeable to retain effluents in the lagoon. Low permeability clay and/ or liners should be used in lagoon construction to minimize effluent leaching to groundwater. Great attention must be paid to their installation.

Spreading Basins

Many wineries treat and discharge process wastewater by flood application to uncropped, bermed areas referred to as spreading basins. This method involves periodic application of wastewater using a technique called rapid infiltration. When wastewater is applied to a spreading basin, it displaces the water in the soil profile by pushing it downward under the force of gravity. The applied wastewater is then allowed to remain in the soil to be treated by natural soil processes.

Irrigation of Vineyard

Some wineries treat and discharge process wastewater by using it as an irrigation supply for the vineyard (Figure 25.3). Irrigation is an excellent method of wastewater reuse that puts both water and nutrients to a beneficialpurpose: crop production. Because crops remove nutrients and salts from the wastewater and soil, this method can also be a positive factor in groundwater protection.

Biodynamic Aerobic Systems

Biodynamic aerobic systems, such as worm beds, can provide aerobic treatment with a considerably lower energy consumption due to the worms providing the aeration and digestion needs, but require larger footprints than bio reactors to accommodate the larger treatment area requirements of worms (Figure 25.4). These systems can have moderate to high capital costs driven by footprint of the system, but have considerably lower operation and maintenance costs and operational demands.

Bioreactors

TNewer technologies such as membrane bioreactors (MBRs) and moving bed biofilm reactors (MBBRs) can provide higher effluent quality with considerably smaller footprint than aerated ponds, due to the use of large membrane surface area, which retains and separates solids and microbes from the water in the reactor after aerobic digestion. These systems still require considerable energy to provide sufficient aeration for aerobic treatment, but typically less than required for large aerated ponds.

Membrane Bioreactors

A membrane bioreactor (MBR) is a biological wastewater treatment system that incorporates a microfiltration membrane on the discharge to remove virtually all suspended solids, bacteria, and protozoa from wastewater. Membrane bioreactors primarily target BOD and TSS. Membrane filtration involves the flow of water containing pollutants across a membrane. Water permeates through the membrane into a separate channel for recovery. Because of the cross-flow movement of water and the waste constituents, materials left behind do not accumulate at the membrane surface but are carried out of the system for later recovery or disposal.

Moving Bed Biofilm Reactor

AMoving bed biofilm reactor (MBBR) is a process whereby wastewater is aerated in the presence of micro-organisms, which grow on the surface of small plastic bio-media. The large surface area of the bio-media provides abundant surface for bacteria to grow and thrive.

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