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Why do we bother Fawlty

In the last 20 years we have noticed a number of developments in the wine effluent treatment business.  Companies come and go, technologies are tested, touted and taper away.  For some time we have been wondering why is winery effluent so difficult to treat?  It is after all mostly biodegradable.  Sure there are some chemicals that come down with the effluent, but by and large the modern winemaker is an extremely competent and environmentally conscious individual.  For these two reasons it is relatively easy to see the bright side of winery effluent treatment.

Why do we bother

By way of analogy and after building and operating more than 30 winery effluent treatment plants, my observations are as follows.

Imagine a restaurant in a small suburb in the village – Stellenbosch is a good example.  The restaurant has a small menu.  Each working night a body of clientele come along and most nights all the food prepared is enjoyed by happy customers.  The restaurant remains successful in that it is not wasting food.  The restaurateur can gauge his food purchases with the amount of meals sold.  The two match quite evenly.

Now imagine another restaurant, also in Stellenbosch.  Here the restaurateur is adventurous.  He provides a vast menu with all manner of options.  He brings in food from a variety of sources and puts together an incredible array of gourmet options.  His clientele love the variety and they walk home with big smiles.  The restaurateur provides the gastronomic feast day after day and each evening he has the pleasure of seeing happy customers.  After a while the restaurateur might notcie that alot of food is not being eaten.  At first he might store surplus food in a deep freeze.  He might make plans to convert vegetables to soup.  Whatever he does, he cannot stop the surplus from accumulating.  As long as he provides a menu that is way bigger than the customer demand, he will be storing and wasting more and more food.  To prevent catastrophe he has to either reduce and match his menu to the customer demand or significantly increase the size of his customer base.

This rather long analogy reflects what happens in winery effluent treatment.  There is nothing wrong with the food.  It is the rate at which it is doled out that presents a problem.  In biological effluent treatment, the customers represent the biomass – the gazillions of bacteria that eat and digest whatever is thrown their way.  The restaurateur is the cellar.    In cellar effluent treatment there are similar choices – either reduce variety or increase capacity.

The nature of winery effluent is such that there is tremendous variation in organic load.  Sewage for example has a COD value of around 700 mg/l.  COD stands for chemical oxygen demand and this tells us how much dissolved organic material is in the water.  The COD of wine is 300,000 mg/l.  This is extremely high.  Coca-cola has a COD of 60,000 mg/l.    The challenge for effluent treatment plant design is that the COD jumps all over the place.  Winery effluent COD can vary from 25,000 mg/l to 200 mg/l.  It all depends on what is happening in the cellar.  Most wine is carefully looked after so there is very little effluent that is pure wine.  It is mostly diluted with water and this would be from the various processes of washing, transferring, rinsing etc.

For the biomass sitting at the restaurant, they can be overwhelmed or underwhelmed.  There is not alot of predictability.  Seasonally there is an oversupply in harvest time and for the rest of the year very little.  But a deluge can happen at any time – activity in the cellar is as varied as there are cars on the road.

This might sound all gloomy and one might ask well what now?  Alas there are not alot of choices.  Non biological treatment will solve alot of problems with variation in organic load.  The challenge at present is that non-biological methods are extremely expensive both in capital outlay and in running costs.

At HWT we recommend bringing in as much sewage as possible, we make the bioreactors bigger and we provide loads of oxygen.  Ambiance is also important – pH must be right, nutrients must be available and most importantly – we ask that teargas is not thrown among the customers.

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