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[quote=Anonymous][quote=Anonymous][quote=Anonymous]Did OP say if this was a decaf latte? No wonder she's worried.

More seriously, I had no idea about milk, and I wondered about the environmental piece given that it would go to the water treatment plant. Found this on a forum where this was being discussed:

[quote]Ex manufacturing chemist here - I think there are two issues: biochemical oxygen demand, and contamination of drinking water by animal products. The second one is not an issue for people pouring milk down the sink into the waste water because the waste water is treated and tested before it runs out to the sea or wherever. The first issue, of oxygen demand, is only an issue if a large volume of milk gets shoved down the sink - the oxygen demand is related to the amount of the stuff, it's not like a poison or anything where small amounts could cause problems. That's why there are rules for businesses and not for private homes. It's not just milk either, it's anything with a lot of edible stuff in it. Some colleagues in the lab next door to us got in trouble when the BOD of our water waste went up significantly one week, and they found out it was because they had disposed of about 100l of growing medium (basically sugary jelly) down the sink. You wouldn't think twice about washing a jelly down the sink, and you'd be right not to - it's the pouring of hundreds of litres that does the harm.
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The city where I live regularly reminds residents about grease and items like wipes ad tampons but has never mentioned pouring milk dow the drain, and this is probably why.

Although I just use sour milk for biscuits or waffles or something. Or if just slightly off I make ricotta.

[/quote]

FYI, aside from the oxygen issue, you're not supposed to pour fats, oils, or grease down the drain and that category includes dairy.  Dairy belongs in the trash, not down the drain.[/quote]

From a licensed industrial wastewater expert:

Household disposal of dairy products are easily disgusted by septic systems or municipal treatment facilities. There is no reason to think it needs special treatment.

Milk as a waste stream has a high BOD 9 g/L (Biological Oxygen Demand), a low nitrogen content and a low phosphorus content. The treatment of the dairy waste stream [b]at most commercial producers[/b] requires the addition of urea and phosphoric acid to aid in the biological digestion. The wastestream is treated to a BOD of less than 200mg\L to be sent to a municipal authority, 30mg\L for irrigation and &gt;10 mg\L for direct water way discharge. Depending on the local regulations total Nitrogen and Phosphorus limits may apply. These limits maybe seasonal as well.

Most household sewage has a low BOD 200 mg/L, and high nitrogen & phosphorus content. It is pretty easy to remove BOD from a waste stream thru biological treatment but Nitrification, Denitrification and Phosphorus removal require a more complicated process, a process that does benefit from a slightly higher BOD than the typical household waste stream. This process is still a biological process but can be augmented with a chemical one at your municipal receiving authority. [b]If you dump a gallon of milk a day down the drain you are probably only adding a 1% to your households BOD lbs. per day and helping to get your households BOD:N:P range closer to the ideal range.[/b]

If your household has a non potable water reuse system, it might not be ideal to pour dairy into that drain. Those systems are incredibly rare and the only ill effect would be on the filter loading. If you have a compost pile, it would benefit from the addition of the dairy products for the added moisture and nutrients.[/quote]

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