Biological pretreatment on site at your brewery is technically possible. However I rarely recommend it and you probably can’t afford it.
I get questions a lot from brewers who assume they need to install a little wastewater treatment plant at their brewery. Yes you can do it, but do you want to? Do you need to? Does it fit within your business model? In almost all cases, the answer to those questions is No.
There are two reasons why onsite biological pretreatment would be installed, to lower municipal surcharges and/or to meet very strict discharge requirements. Surcharges can get expensive for sure, but there is no maintenance, employees, etc., so the ROI of onsite treatment often winds up not being attractive enough. An example of a very strict discharge requirement would be 300 mg/L BOD and 300 mg/L TSS, not unheard of and there is no way for a brewery to meet this requirement without onsite treatment. But is this the right site for you?
The best option is almost always to have someone else treat your wastewater for you- especially if they’ll do it for free. Doing what you can to make the people at your municipality happy to treat your wastewater for you is a great deal. My best piece of advice for any brewer may be to ‘play nice’ with the regulatory authorities you have to deal with. They may give you rules, laws, and limits to abide by, as well as charge fees- and you might not agree with them all. But smile, be courteous, professional, and try to see things from their perspective. Do not get in to an adversarial relationship. They have lawyers on retainer and they probably know their laws better than you do. All of this doesn’t mean don’t try to negotiate- just be professional. Municipalities can treat your wastewater cheaper than you can, they have a better tolerance for low payback projects, plus they already have the rate-payer funded equipment and staff.
There are two main categories for wastewater treatment, aerobic and anaerobic. We’ll focus on aerobic here, anaerobic is possible but usually only at a bigger scale (150,000+ bbls/yr).
The very short story with aerobic pretreatment is adding a lot of air to a wastewater tank, this provides oxygen to bacteria and those bacteria consume the sugar and alcohol (BOD) in your wastewater, thereby treating the wastewater. Sounds easy, but remember people get PhD’s in this stuff. One byproduct of aerobic treatment is sludge, the wastewater equivalent of spent yeast. And it’s a lot of sludge. Essentially what you’re doing with aerobic pretreatment is converting soluble BOD in to solids (sludge), and this sludge needs to be disposed of.
And of course it’s more complicated than that. The bacteria in any treatment system are alive and the wastewater has to meet certain criteria in order to keep them alive and thriving. You will need upstream equipment, such as a lift station, solids screening, EQ tank, pH adjustment, and possibly odor control. And you’ll need equipment downstream of the aerobic system, such as settling, sludge removal, sludge storage. And of course controls to run all of this and an employee who knows how to operate and maintain all of this stuff- and this person may be required to have a wastewater treatment plant operators license. Does it sound expensive yet? And there are added expenses of electricity, possibly coagulants, and space.
What about anaerobic pretreatment? I have a soft spot in my heart for anaerobic treatment systems at a brewery. The very short story is bacteria consume the sugar and alcohol in the wastewater and through a two step process generate reusable, renewable biogas. And of course brewers use a ton of gas in the brewery for wort boiling and hot water generation. That seems like a win-win! But, and I’m beginning to feel repetitive, it’s more complicated than that. Anaerobic pretreatment generally only makes sense for brewers above 150,000 bbls/yr production, and even then it’s a hard sell.
A story I am aware of is a brewery installed an anaerobic treatment system, part of the justification was current natural gas prices. As we’re all aware natural gas prices fell, and the brewery is generating biogas at a higher cost than they can buy natural gas. Biogas is greener for sure, but we’re all in business and economics rule the game. Another part of their justification was public perception and doing the right thing. Over time they learned memories are short, not many people will support a business based solely on sustainability, and sustainability gets harder to communicate as a brewery moves farther afield.
Lastly, what about avoiding the city sewer and discharging direct to an adjacent river or stream? Not impossible, but it would be and super expensive a nightmare to get through permitting and operations. Discharging direct to surface water would get your brewery under the jurisdiction of the federal EPA, and your brewery would have it’s own NPDES permit. And then there are Total Maximum Daily Load (TMDL) limits. This isn’t what you want, I am not aware of any craft brewers of any size, anywhere doing this. But, people still ask about it.