Wastewater Treatment for Wineries and Achieving a Sustainable Operation
by Mitchell Laginestra, GHD
Introduction
Wineries present a challenge for treatment of wastewater. Vintage runs for only 3 months a year, during
which time the bulk of wastewater is generated (typically over 80 %). The rest of the time wastewater is
significantly lower in strength and volume. Wineries are typically located in rural locations and consequently
treatment systems involved a series of lagoons, followed by irrigation of effluent. This is not always the case,
and there are occasions where minimal treatment is undertaken, and poor quality wastewater irrigated.
Biological treatment of wastewater, via lagoons or conventional processes enables improvement of
wastewater quality by reducing contaminants from the stream prior to application. Biologically treated
effluents are typically suitable for irrigation. By building treatment barriers into the treatment process, then
more contaminants would be reduced, which potentially enables a wider use for the effluent. Lagoon
systems can remove the bulk of BOD and SS, but filtration and other physical / chemical processes can
enhance the quality to minimise irrigator blockages or enable other uses.
Lagoons – Types and Purpose
Wastewater treatment lagoons serve municipal and industrial applications around Australia. The main
advantage of this type of system is their simplicity to build and operate. Conventional wastewater treatment
typically involves a mechanical aeration device to provide oxygen for breakdown of organic matter contained
in the wastewater.
Lagoons are a natural biological treatment processes and are appropriate for wineries as they provide:
» Simple operation;
» Low energy consumption compared to more conventional systems;
» Natural pH buffering;
» Some nutrient uptake; and
» Solar induced disinfection.
Being non-mechanical systems, the detention time (and subsequent surface area / footprint) is significantly
greater than conventional mechanical treatment systems.
Lagoons can comprise a range of operating parameters, and are distinguished largely by the dissolved
oxygen (DO) of the layers within the ponds, which in turn, is dependent on the organic and hydraulic loading
of the pond system.
Types of ponds include anaerobic, facultative, aerobic and maturation. Typically facultative or mechanically
aerated ponds are used for winery wastewater
Anaerobic ponds are designed to cater for high organic loading, and are typically absent of dissolved oxygen
and involve long detention times (to cater for degradation of organic matter). Anaerobic decomposition
involves the breakdown of organic wastes to gas (methane and carbon dioxide) in the absence of oxygen. As
such they are typically used for high strength waste (and vintage period winery wastewater falls into this
category). They also provide an opportunity to obtain a beneficial by-product – biogas, which can be used to
generate electricity.
Facultative ponds involve an aerobic upper layer and anaerobic lower layer. The aerobic system is
maintained through algae and wind action. However, mechanical aeration is often employed for larger
wineries to provide aeration within a smaller pond. Aerobic systems involve biological breakdown by aerobic
micro-organisms, which convert the matter to inert solids, new cells and carbon dioxide. They are typically
odour free (reduced), but anaerobic systems typically are characterised by odour generation, and most
modern anaerobic systems are contained to collect the generated biogas and contain odours.
Maturation ponds are shallower than other ponds and allow algal development for oxygen transfer and
disinfection via sunlight UV.
Pond systems typically comprise a treatment train, which involves a series of ponds – anaerobic / facultative,
aerobic / maturation. The appropriate train / series is dependent on loading, and ponds must be properly
designed to cater for oxygen requirements to reduce the BOD to acceptable levels as well as minimise
odours.
Lagoon treatment systems … ..
common and appropriate, but
beware limitations and
operational requirements,
especially during vintage
Largely because of the above advantages of lagoon system they are generally regarded as the most
sustainable type of treatment process (except in cases where there are space limitations).
Issues with Lagoons
Detention time is important for any biological system and this must be catered for in the design. Area
limitations can be an issue, although there is an offset between detention time and mechanical aeration
requirements.
Often neglected in design of wastewater treatment systems are the residuals management requirements and
also the operator involvement. While lagoon systems are very forgiving, the vintage periods present much
greater loading, and unless spare aeration capacity is brought into play, then effluent quality can deteriorate,
as a result of oxygen demand exceeding supplied mechanical oxygenation. This typically results in odour
generation (not quite the attraction for visitors to the cellar door).
Wastewater treatment generates residual solids (slurry) stream as a result of the organic matter being
degraded (inert solids and excess microbial biomass). This must be removed from the lagoons periodically
(desludging). Many operators seemingly take the view that the sludge breaks down and simply disappears –
this is not the case and lagoons which have excess sludge accumulation are subject to operational difficulties
including substandard performance, odour generation and sporadic release of solids into the effluent stream.
Lagoons should be partially desludged every 2 – 5 years at the most. Desludging typically involves removing
of the liquid slurry via pontoon mounted pump with delivery to dewatering system and disposal of spadeable
solids at landfill or spread on land.
Residuals generated during wine production (marc and lees) present another issue, and unless dealt with
within a short period of time also can putrefy and result in odours. Typically land spreading is employed to
dispose of the marc, but organic loading of land can be an issue, and there are limitations.
However, being organic, they are biodegradable, and consequently present an opportunity to provide
controlled stabilisation via an anaerobic system, the same as that used in wastewater. This provides a
beneficial by-product (biogas) to generate electricity to off-set the costs associated with the treatment and
waste disposal (as well as a means of residuals management). They may also be used in production of a
composted product (an aerobic process), which provides a good source of soil conditioning material.
Composting may be undertaken on-site or off-site at a licensed operator.
For anaerobic digestion, as marc and less are solid wastes, greater mixing / slurry generation would be
required to increased process efficiency (which is a higher level of efficiency typically provided in a simple
lagoon system). This may involve a constructed reactor with mixing and involve elevated temperatures
(anaerobic microbes operate optimally at 30 – 35oC). The resultant biogas can be used to generate energy
for this purpose. Wastes of low BOD concentration may not provide sufficient methane for heating, and a
supplementary source of heat is necessary (which will incur additional cost). However, heating is only
required when there is a need to increase the efficiency of the anaerobic process, and thermal heat from an
electricity generation process may be used for this purpose. Other uses for the generation of power would be
hot water generation and general electricity use (either for aeration of the treatment system or power / lighting
around the winery). Relying on biogas production during non-vintage periods can be an issue, so either there
must be gas / electrical supply back up, or the operator must consider taking other supplementary waste
products for digestion.
Anaerobic lagoons are rare at wineries, because of the vintage / non-vintage period (the treatment system
receives a high volume and organic load for only 3 months, and receives a low volume / organic load for 9
months). There are ways around this, and what is typically overlooked is that anaerobic systems can lie
dormant for long periods of time (although start-up must be managed to avoid shock loading at the onset of
the vintage). During the projected digester feed shortfall (non-vintage period), feed to digestion could be
supplemented with waste solids from the aerobic wastewater treatment, and perhaps other liquid wastes at
the site or external to the site (dairy or cattle wastes).
Sustainable Operation
Like everyone in industry nowadays, there is an onus to find a sustainable solution in all activities undertaken.
Whilst there are a number of definitions, it is really about finding the right cycle and achieving environmental,
economic and social outcomes.
There are broad opportunities to achieve a largely sustainable operation at wineries through:
» Treatment of wastewater to produce an effluent quality for irrigation (making use of the used water, and
regarding it as a resource rather than a waste product);
» Application of residuals by-product use for compost production to provide a rich non-putrescible organic
resource which may be used to improve soil qualities / general beneficial application.
Achievement of a sustainable operation may be further enhanced through application of anaerobic digestion
(for wastewater residuals and marc / lees) for generation of biogas, which would be used for energy
production / use at the winery and wastewater treatment plant.
This approach makes good economic sense as well as providing environmental and social improvements.
There is a significant outlay in terms of setting up such an operation, and this has, in the past, contributed to
avoidance of the approach. However, if you take into account the costs of residuals management for marc
and lees, as well as the potential cost of rehabilitating land, which has been stressed from sub-standard
effluent or other wastes, then the payback is very short.
Potential Sustainable Operation
WINERY
Thermal energy
Wastewater
Effluent
Aerobic
Treatment
residuals
Treated
Effluent
M arc / Lees
Anaerobic
Treatment
Cogeneration
Gas
residuals
Dewatering
Dew atering
Irrigation
Electrical energy
Composting
Soil enrichm ent
program
Contact
Mitchell Laginestra is GHD’
s Technical leader for Industrial wastewater Management, and may be contacted
at his e-mail address: mitchell.laginestra@ghd.com.au