116
M. B. Johnson and M. Mehrvar
Effluent disposal can be divided into three main categories: direct discharge to
surface waters, subsurface discharge and irrigation discharge. A single winery may
use one or more disposal methods. If the wastewater is conveyed to an offsite treatment system, such as a municipal WWTP, then the ultimate disposal method is that
used by the offsite treatment system. In such cases, the treated WWW effluents
represent only a fraction of the total effluent discharged by the municipal treatment
system.
Discharge to surface waters and subsurface discharge, typically via a leaching
bed, represent a direct return of treated effluent to the natural environment. Irrigation
discharge, where treated effluent is used to supplement or meet vineyard irrigation
needs, is the most common reuse strategy used at wineries.
Due to the seasonal nature of viticulture and vinification, peak WWW generation
rates do not coincide with peak irrigation needs [56]; therefore, WWW effluents that
are reused for irrigation are typically stored in large earthen lagoons that provide
storage during the non-irrigation period [35]. These can be part of the treatment
process (providing biological treatment), or simple effluent storage ponds. Due to
public health safety concerns, effluent reuse for irrigation is generally restricted to
winery process wastewater and not sanitary sewage [56], although irrigation reuse
of combined process and sanitary wastewater is sometimes possible if adequate
disinfection is provided [35].
Utilizing WWW for irrigation can have negative impacts on soil conditions that
can affect soil quality and increase the potential for runoff. In particular, the build-up
of Na
+ and K
+ ions, which are often present in large concentrations in WWW, can
fill void spaces in the soil thus changing its hydraulic conductivity [33]. Typical fullscale WWW treatment methods do not remove ions and, as such, cannot eliminate
this potential negative impact [13, 15]. In addition, the application of WWW effluents
for irrigation has been found to change the types of microorganisms present in the
soil [49].
The ability to reuse effluent for irrigation and the development of maximum application rates (generally expressed as mm/yr) can only be determined through sitespecific assessments [13]. These would need to consider the particular soil type(s)
present, prior application of WWW effluents, and the characteristics of the vines,
particularly rootstocks. Despite these potential limitations, evaluation of treated
WWW effluent quality from 18 wineries in California concluded that treatment
methods, including physicochemical and biological, were able to produce effluent
of high enough quality for irrigation reuse purposes [13]. Other reported WWW
effluent reuse for irrigation includes jurisdictions in Italy [47], South Africa [52] and
Canada [35].
M. B. Johnson and M. Mehrvar
Effluent disposal can be divided into three main categories: direct discharge to
surface waters, subsurface discharge and irrigation discharge. A single winery may
use one or more disposal methods. If the wastewater is conveyed to an offsite treatment system, such as a municipal WWTP, then the ultimate disposal method is that
used by the offsite treatment system. In such cases, the treated WWW effluents
represent only a fraction of the total effluent discharged by the municipal treatment
system.
Discharge to surface waters and subsurface discharge, typically via a leaching
bed, represent a direct return of treated effluent to the natural environment. Irrigation
discharge, where treated effluent is used to supplement or meet vineyard irrigation
needs, is the most common reuse strategy used at wineries.
Due to the seasonal nature of viticulture and vinification, peak WWW generation
rates do not coincide with peak irrigation needs [56]; therefore, WWW effluents that
are reused for irrigation are typically stored in large earthen lagoons that provide
storage during the non-irrigation period [35]. These can be part of the treatment
process (providing biological treatment), or simple effluent storage ponds. Due to
public health safety concerns, effluent reuse for irrigation is generally restricted to
winery process wastewater and not sanitary sewage [56], although irrigation reuse
of combined process and sanitary wastewater is sometimes possible if adequate
disinfection is provided [35].
Utilizing WWW for irrigation can have negative impacts on soil conditions that
can affect soil quality and increase the potential for runoff. In particular, the build-up
of Na
+ and K
+ ions, which are often present in large concentrations in WWW, can
fill void spaces in the soil thus changing its hydraulic conductivity [33]. Typical fullscale WWW treatment methods do not remove ions and, as such, cannot eliminate
this potential negative impact [13, 15]. In addition, the application of WWW effluents
for irrigation has been found to change the types of microorganisms present in the
soil [49].
The ability to reuse effluent for irrigation and the development of maximum application rates (generally expressed as mm/yr) can only be determined through sitespecific assessments [13]. These would need to consider the particular soil type(s)
present, prior application of WWW effluents, and the characteristics of the vines,
particularly rootstocks. Despite these potential limitations, evaluation of treated
WWW effluent quality from 18 wineries in California concluded that treatment
methods, including physicochemical and biological, were able to produce effluent
of high enough quality for irrigation reuse purposes [13]. Other reported WWW
effluent reuse for irrigation includes jurisdictions in Italy [47], South Africa [52] and
Canada [35].