Capito had never considered such a problem before, and for once showed a bewildered expression. After a while, he said helplessly, "Even if the wastewater from refining iron ore is not discharged into the river, it might still end up in the river if we discharge it somewhere else!"
"I have a solution you can try," Maximus said confidently. "Dig several big pits next to the Iron Workshop, and place some charcoal at the bottom of the pits. Discharge the wastewater from iron refining into the first pit, let it settle for a while, then discharge it into the second pit, and let it settle again, then discharge it into the third pit...
This way, after the wastewater has cycled through these pits, most of the mineral residue will have settled in the pits, and the relatively clear wastewater can be discharged into the river."
Capito pondered for a while and asked, "Why put charcoal in the pits?"
