Waste water is increasingly becoming an issue facing wineries. New and expanding wineries are subject to increased scrutiny by the Regional Water Quality Control Board (RWQCB). Part of the new or expansion plan is a detailed review and design of the proposed waste water system. The following article delves into this gray aspect of the winery business and sheds light on current technologies including their limitations and also introduces the reader to a newer more optimized waste water reduction method.
In the process of making wine, waste water in generated. The waste water is generated during various phases of the wine making process and occurs throughout the year. The phases include crush and bottling operations but also occur during barrel and tank washing. The waste water is high in BOD (biological oxygen demand) from the sugars of the wine and crush, and also high is suspended particulate including grape skins and pieces of grapes.
Traditionally the approach has been to utilize a septic system for waste water disposal. And to a limited extent this works, but unfortunately or fortunately with the growth of the wine industry production increases, and so does the loading to the system which leads to system failure as indicated by foul odors and ground water contamination as the leach lines become saturated with solids which degrade slowly.
The type of degradation that occurs in a septic system is anaerobic, without oxygen. The degradation occurs when bacteria and microbes consume the sugars and particles in the effluent. These bacteria occur naturally in the soil and with enough time and without overloading the septic system with too much food, can get the job done.
Another traditional approach is to utilize ponds to degrade the waste water produced by the winery. These ponds known as facultative ponds use both anaerobic and aerobic bacteria to digest the effluent. The ponds digestion ability can be enhanced with the addition of aeration, usually floating aerators, which resemble small outboard motors 5-50 hp, mounted on floatation pontoons. The ponds tend to be large in nature often measured in acres, and unfortunately they often displace quality vine acreage.
The inherent weaknesses in a ponding system is the degradation of BOD requires weeks, which makes the ponding system large. With the large levels of BOD at crush along with the usual warm weather in October, the ponds often turn septic as indicated by their foul odor. The large organic material along with the natural acidity of the wine reduces the pH leading to the production of sulfides and the associated rotten egg odors. The ponds tend to be in balance and a sudden increase in food versus the normally supported level of microbes throws them out of balance and the recovery time is also measured in weeks.
A newer more efficient means of reducing the levels of BOD in the waste stream is known as a Bio Reactor system. These systems are small and compact often measured in feet in size. They are designed to optimize the biological degradation of the sugars in the waste water. They are similar in ponds with the exception that they require much less size and the degradation occurs with much less time. They are not new in concept and are a common way municipalities degrade the BOD in sewage to meet federal standards.
The Bio Reactor system is composed of several key components each equally important to the system and they include a screening system either a parabolic screen or preferably a rotary screen, this removes the larger particles, which take a longer time to degrade, from the effluent.
A means of retaining the effluent for the required digestion time is one of the most essential components of a successful system. For certain waste streams, the BOD levels are reduced by 80% with 24 hours. For example a BOD level of 5000 ppm, common during crush is reduced to 1000 ppm within one day and 200 ppm within two days. The retention can occur either above ground in tanks, polyethylene, epoxy coated steel or stainless steel, with polyethylene being the least expensive and readily available, or below ground in a vault or cement basin.
The next key component in the system is the aeration system this is composed of a blower and diffusers. The blower is designed to deliver large volumes of air at low pressures. The diffusers are designed to maximize the oxygen transfer to the effluent. The diffusers are very important and directly influence how efficiently the blowers horsepower is utilized in oxygen transfer to the water. The ideal diffusers produce the smallest bubble, the small size of the bubble has the largest proportion of surface area and the most contact with the effluent resulting in the largest rate of absorption.
The digestion of the effluent is controlled by the ratio of food to microbes, this concept is one reason why a Bio Reactor is the most efficient means of reducing waste water. A clarifier following the last Bio Reactor tank, collects the biological sludge, concentrated microbes. These microbes when feed back to the incoming food source. The fresh effluent, high in BOD, is quickly digested as the concentrated microbes come in contact. The ability to return the highly activated sludge is a major control feature to insure prompt and predictable digestion without regard to the incoming levels of BOD.
While there are times during operation that the sludge is returned to the primary bio reactor, there are other times when there is a decrease of incoming BOD where the microbial level should be reduced. The sludge is wasted or disposed of and there are various means of performing this operation. The sludge is a thick slime with a consistency which varies from gelatinous to that of tomato soup. The sludge can be dewatered effectively in a plate and frame press for ease of transportation, or disposed of by adding directly to a composting pile which accelerates the decomposition or organic matter. The amount of sludge produced is approximately a half a pound per pound of BOD reduced.
The remainder of the system includes properly sized feed pumps to transport the effluent as required, pH control, and the addition of nutrients such as phosphorous and nitrogen if required.
The Bio Reactors can be designed in a modular format, allowing part of the system to be closed down when not required and/or easily expanded with future winery growth and production. If a ponding system exists with marginal performance due to increased loading, then a Bio Reactor up stream will reduce the loading to the pond. Often the reduced BOD effluent will flow to a small irrigation pond for direct land application. These ponds do not have to be lined as the BOD has already been greatly reduced
The above is a brief overview of the most effective and controlled means of reducing the winery effluent. While it may seem more involved than a simple ponding or septic system this is directly offset by the space efficiency, the reliability of operation and BOD reduction. The Bio Reactor system is becoming increasingly attractive to wineries in direct proportion with the increased number of wineries, the increased cost of vineyard acreage and the increased scrutiny of the RWQCB of the waste water plans for new and expanding wineries.
The article was developed by Glenn Wensloff, a waste water engineer, who heads Elutriate Systems. They are located at 1398 Deer Canyon Road, Arroyo Grande, CA 93420. They have a web site www.Elutriatesystems.com, where more articles about waste water are posted along with a list of services and products they provide. They provide an onsite review of your existing waste water system and very practical and low costs means of improving the systems performance. They also work with new and expanding wineries to meet the ever increasing effluent restrictions imposed by the RWQCB, city and county agencies. Elutriate Systems is offering a free booklet “An Operators Guide to Winery Waste Water Systems” please call for your copy.