The purpose of brewery wastewater pretreatment is to keep the brewery running. Period.
Does that make sense? Brewery wastewater is not the same a domestic wastewater. Restrictions will often apply, so the purpose is to comply with those restrictions so you can keep the brewery running. As simple as that.
In many cases, small breweries and brew pubs do not receive wastewater restrictions from the city/county or agency at start up. However as the brewery grows the impact of the wastewater will become noticeable at the local wastewater treatment plant- especially if it’s a small plant. The local authorities will start talking about surcharges, pH control, and in rare cases loading restrictions. Don’t fight it, these restrictions are common.
One thing I have noticed in the course of doing this type of work; big cities are usually only concerned about infrastructure protection and making money. This means pH adjustment and surcharges. Small cities are concerned about pH and money, but also loading. No surprise really. The collection system is not designed for really low or really high pH. And of course, who doesn’t want to make money? Loading restrictions might be an issue if the treatment plant is small or if there is a lot of growth in the area. What is loading? Read this post on this website for more.
Of course there can be a lot of ancillary reasons for wastewater pretreatment at a brewery. Such as heat recovery, methane generation, nutrient cycling on a farm brewery, and to give the brewery a green image. Breweries on septic is a topic for another post, but treatment of some sort is usually needed ahead of the drain field.