I ran a small fab on the peninsula back in the day, and we certainly didn't dump any trico down the drain. We did put a small amount of propanol (used to switch

I ran a small fab on the peninsula back in the day, and we certainly didn't dump any trico down the drain. We did put a small amount of propanol (used to switch from a water rinse to trico drying) down, but that's pretty harmless. The trico was taken away by a reprocessing company. It was still essentially pure - some of it contained a bit of dissolved photoresist or beeswax. I read through the OP - he's making good choices and doing it much as we did fifty years ago. I would have killed to get that maskless photolith setup, though. For a small fab (three furnace tubes, two fume hoods), the main issue is acids from photoresist ashing, wafer cleaning, tube etch cleaning, and metal etching. These are easily neutralized with a vat of marble chips built into the plumbing under the fume hoods. If you are doing this, avoid epitaxy, which involves arsine and phosphine. I would say never attempt those! You can buy epi wafers. Either use spin-on dopants like he did, or use oxidized boron nitride wafers and small amounts of phosphorous oxychloride like we did. The effluent from a plating facility or a dry cleaning establishment would be far more concerning. Our furnace and photolith operation fit in a 20 x 30 ft room. It was one of the leading operations of its kind in the world at that time.