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Treatment System Basics and Maintenance

Many wineries in California discharge their wastewater to land or the subsurface. Others send their wastewater to a municipal system (POTW) or have it hauled away, where it is treated at a centralized facility.


Regardless of the system type, it is important to understand how your system works, what its design capacity is, and how to maintain and monitor it for best performance.

Treatment Options

Winery wastewater treatment systems can range from ‘high-tech’ to ‘low-tech’, and the particular choices of treatment equipment and processes will be determined by the winery’s specific needs and constraints. Always consult a technical expert when designing or upgrading a wastewater treatment system.


Systems should be designed to meet the specific needs of the winery, including cost considerations, wastewater volumes, water quality characteristics, regulatory requirements, and site conditions (including soil types, depth to groundwater and precipitation rates).

Be sure the use of your system complies with applicable regulations in your area (see sidebar). In addition to certain design specifications, regulations may include discharge limits as well as monitoring and reporting requirements. If you send your wastewater to a publicly owned treatment works (POTW), be sure you understand the terms of your service, which may require some pretreatment.


Click the button at right for detailed discussion of wastewater treatment options, including facultative ponds, anaerobic and aerobic systems, membrane treatment processes, and solids handling.

Statewide General Order

for Wineries: 

In January 2021, California’s State Water Resources Control Board adopted a Statewide General Order for Wineries. This permit includes constituent discharge limits and monitoring and reporting requirements, among other specifications. Most wineries that apply their wastewater to land or the subsurface will be required to apply for coverage under the Order.

For more information about the Statewide Order, visit CSWA’s Regulatory Tool or read Kennedy Jenks’ short summary.

Discharging to Land

Commonly used land application methods in California include discharge through a septic tank and drainfield system, irrigation of wastewater on agricultural crops, land application via spreading basins, and constructed wetlands. These approaches require varying levels of day-to-day management, but all necessitate careful attention to site selection and wastewater constituent characteristics.

Selecting a Treatment System

For useful background on selecting

a suitable treatment system for your winery, including examples of innovative treatment technologies, consult Sustainable Winegrowing British Columbia’s Winery Process Wastewater Management Handbook.


The Water & Wine online platform also features helpful tools and case studies.

Maintaining and Monitoring a System

Maintenance and monitoring needs vary across contexts, but the following basic considerations can help you prevent harmful (and costly) system failures.

Tracking Wastewater Volume

Keep an up-to-date understanding of how much water is flowing to the various parts of your treatment system, to ensure that its design capacity is not exceeded. Be sure to account for any precipitation that may enter the wastewater stream, as this will add to the total. It is also a good idea to closely track wastewater flows during crush period, and to calculate peak daily flow amounts. Remember that wastewater flows can vary significantly from year-to-year, and consider accounting for future growth in your wastewater system planning.


Tracking Wastewater Composition

Constituent concentrations in winery wastewater can vary widely over the course of a year, especially during crush. It is important to understand your wastewater composition, particularly with regard to the key constituents of BOD, Salinity and Nitrogen. The California Statewide General Order for Wineries specifies certain monitoring requirements depending on the situation, including sampling for BOD.


Establishing a Sampling Regime

Your sampling approach should be catered to the needs of the winery in addition to regulatory requirements. It is essential to locate strategic locations for sampling to occur (have you located your septic tank’s inspection port?) as well as the tools that are needed to do the job right. Carefully consult the information you receive from vendors and laboratories.


Separating and Handling Solids

Treatment systems may benefit from a solid separation stage in addition to the ‘upstream’ diversion of coarser solids within the winery. This could consist of a finer screening stage before solids reach a pond or septic tank, to lower organic matter content and prevent clogging of drainfields or irrigation equipment.


Inspecting System Components

Identify each component of the wastewater treatment system and establish a regular inspection routine, recording your observations in a log book. This will help identify any slowly occurring changes in the system and will also allow identification of operations and maintenance needs (such as periodic septic tank pumping). Even if you rely on an outside vendor to maintain your system, it is a good idea to keep tabs on your equipment to make sure it is operating safely, effectively and efficiently.

[Adapted from Comprehensive Guide and Winery Process Wastewater Management Handbook.]

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