Agriculture Reference
In-Depth Information
waters, to avoid polluting those waters. Consequently, the dual incentives for
treatment of wastewater are
1. To recover a substantial fraction of winery wastewater treated to a level
suitable for irrigation
2. To remove as much of the waste organic matter as possible, which can
then be spread on pasture or composted and used in the vineyard
In addition to wastewater, another form of winery waste is marc or pomace
(crushed skins, seeds, and stems), which can be composted and spread in the vine
rows (see “Cultural Practices for Organic Viticulture,” chapter 3). Whether the
waste is in liquid or solid form, there is the potential for substantial amounts of
organic matter to be returned to the soil. Box 5.5 gives examples of the amounts
of organic matter that are available in liquid or solid form and their beneficial use.
Soil Factors to Consider in the Disposal of Winery Waste
The general principle to follow is to reduce, recycle, and reuse. Implementing this
principle involves minimizing water use, segregating waste streams of different
strength (e.g., keeping stormwater separate from wastewater), treating the water
and solids recovered, reducing the amount of cleaning agents used in washing
equipment, and choosing cleaning chemicals with low Na concentrations.
The variability of the waste stream is a problem for wastewater manage-
ment. The biological oxygen demand (
BOD
) is determined by the amount of
O
2
required by microorganisms to oxidize organic matter in the wastewater. It
is expressed as a concentration of biodegradable organic matter, which ranges
from 1,000 to 12,000 mg/L. Box 5.5 outlines treatment methods that are suitable
for small wineries. For much larger wineries (>10,000 t crushed), settling ponds
are used first to remove some of the organic matter and reduce offensive odors
through anaerobic decomposition. Some of the organic N and P, along with much
bacterial residue, settles in the sludge and nitrate N is lost by denitrification. These
ponds are followed by aerobic ponds that are kept aerated to promote a balance
between algal and bacterial growth, achieving a further reduction in
BOD
, N, and
P. The effluent water from these ponds can be used to irrigate woodlots or pasture.
The sludge from the ponds can be spread on agricultural fields or composted and
used to build up SOM in the vineyard. Treating wastewater to a sufficiently high
standard for irrigation in vineyards is expensive, costing as much as $4,000/ML
in Australia.
Where wastewater is intended for land disposal,
BOD
is less of a limiting
factor than the total dissolved salts (
TDS
) and sodium adsorption ratio (
SAR
)
of the water (see box 2.4, chapter 2). This constraint applies equally to the use
