Many wineries and fresh cut processors utilize ponding in their waste water plan. When used correctly this is a very efficient method of reducing BOD (biological oxygen demand) in your waste stream. And when properly controlled your pond should not to stink. Further by allowing your pond to become odifourous, you are actually creating a counter productive situation. Not only is the BOD not being reduced effectively, but your neighbors complain and soon the Air pollution control district and Water Control district begin to investigate.
BOD is released whenever fruit or vegetable are cut. The amount of BOD varies with the produce being processed. But whether it is Grapes, Salads, Carrots, Garlic, Bell Peppers, Olives, Apples, Oranges, Lemons, The sugars from the process are released into the rinse water. Some of the BOD is dissolved into the water and some is carried along with particles.
Ponding is a very simple and efficient method of reducing BOD. With proper aeration, pH control and microbes, your pond can quickly and efficiently digest and degrade the complex sugars making up the BODís.
BOD is a parameter used by the federal government, who passes it down to the state and municipality to measure and quantify how dirty or contaminated a waste stream is. There exist three distinct scenarios in the fresh cut industry depending on whether your facility discharges to a municipality, or have ponds which are allowed to percolate or have enough acres to reapply your waste stream to the land.
Municipalities; Typically they charge the wineries and fresh cut processors for both water flow and also the BOD level of your waste stream. Review your current billing and determine what is your BOD surcharge.
Ponds that can percolate; Some fresh cut processors have facilities with ponding that is allowed to percolate. Hopefully this has been established and approved by the State Water Quality Control Board. This is a favorable condition if the processing facility is land locked and is removed from the growing fields. The ponding for such a facility may still require 2-5 acres. The State Water Control Board will require you to monitor and quantify the BOD level from your process. Once you get close to your ponds BOD reduction capacity this may begin to hamper the ability to expand production, and your ponds BOD reducing efficiency may begin to cost you money in lost processing opportunity.
Ponds that are used before land application; This is the common with processing facilities located close to the growing fields. The process waste water is used to irrigate. The State Water Control Board will require that you monitor the BOD per acre. Once you exceed the pounds per acre of BOD you have two options, buy more land or improve your ponds BOD removal efficiency.
For all of the above scenarios it becomes apparent that a properly maintained pond will save you money, and contribute to your organizations ability to expand and grow.
A pond is a biosphere. It is alive with microbes, algae and plankton that when properly maintained consume BOD. There are four parameters that effect the health of your pond,
1) pH; As is expected for optimum pond performance a pH of fresh water is expected. Water has a pH of 7, but may range from 6.5 to 7.5 depending on location.
2) Aeration; The proper amount of aeration is very important. The obnoxious bad pond odor, is directly a function of insufficient aeration. Based upon you BOD loading to your pond, your oxygen demand can be determined, and the proper aeration equipment specified.
3) Food Source; The microbes eat the food found in the water. This food source is the above mentioned BOD. Along with this they are susceptible to what is in the water, i.e. chlorinated cleaners, acids or caustics, oils etc. Fortunately the volume of water in a pond dilutes most upsets from being catastrophic to your ponds.
4) Microbes; It is important to maintain a young, renewed bio mass for optimum BOD reduction. By feeding microbes to your pond you are skewing the population of microbes to those that reduce the most BOD. More advance forms of microbes will consume smaller microbes versus consuming BOD. This is a double edge sword in that your BOD is not getting reduced while the microbes that could reduce your BOD are getting reduced.
When used and operated correctly a ponding system works well. And remember if they smell they are not working very well at all. The odors can stopped with proper pond management
The author Glenn Wensloff heads up the firm Elutriate Systems, a company specializing in designing, installing, permitting, starting and operating waste water systems for wineries. Additional information including previous projects and published articles are posted at www.elutriatesystems.com for your review.