An equalization tank can be a great solution for a medium sized brewery- or even large ones. This type of tank offers a lot of options at a low cost.
This page describes EQ tank operation. See this page for information about the tank itself.
You can think of an EQ tank like a wide spot in the pipe, a place to do something to your wastewater. Like what? The short answer is to do what you need to do in order to comply with your discharge permit.
Most common would be pH adjustment. In short, water from your lift station enters the EQ tank, the tank recirculates, and chemicals are added to bring the pH up or down. Once the pH is in range, discharge to sewer. pH adjustment is usually about protecting the underground sewer pipes from corrosion.
Like most living things, a wastewater treatment plant likes a steady state. A typical day of flow at the receiving end of a wastewater plant (called Headworks) will have a spike of flow between 6-8 AM or so as people take showers, make breakfast, etc. Then there is a drop in flow with a small spike around lunch time. Another drop, then a big spike as people get home from work, make dinner, do dishes, give kids a bath, etc. Then flow really drops off over night before the cycle starts again the next day. This is called diurnal flow, a famous exception to this is halftime of the Super Bowl. This type of variation is engineered in to the wastewater plant.
A brewery has it’s own version of diurnal flow, usually with flow and load peaking during the work day and dropping off to zero overnight and weekends. Combined with the rest of the city’s flow, a graph of influent flow would look virtually unchanged with or without the brewery. However, depending on local conditions a graph of BOD and TSS load may look a lot different with and without the brewery, a spike with the brewery, no spike without. (See here for an explanation of load.)
One of the factors an EQ tank can help control is this diurnal flow. For instance the EQ tank can store wastewater produced during the day/week and discharge it overnight, or evenly 24/7. This levels out those spikes and that can be tremendously helpful to a small wastewater treatment plant.
Related to the above, another way an EQ tank can help is some municipalities will give a brewery a flow limit; possibly as low as 5 gpm! The EQ tank can absorb excess water in the headspace of the tank and discharge to sewer at that constant rate- until the tank is empty or there is a high level alarm.
One last item and EQ tank can help with is temperature control. Some towns are strict with regards to temperature. For instance most municipalities say wastewater can be no higher than 150F, or causing a temperature higher than 104F at the POTW (Publicly Owned Treatment Works (wastewater plant)). This is reasonable. However a few towns I have worked with have a different interpretation and the refer to the POTW as the sewer pipes and the treatment plant. This is much more restrictive and more difficult to comply with.