The Teneria San Miguel tannery facility was threatened with shutdown. Its waste water had high levels of heavy metal (chrome) and other organic concentrates, which were ultimately discharging into a local river, which had become terribly contaminated.
The Teneria San Miguel processed animal hides through a chrome-tanning process which produced a waste water stream containing exorbitant levels of organics and chrome.
Water Energy technology was used to bring the tanning facility's wastewater stream into compliance with established discharge parameters.
The first step toward reducing the pollutants was to separate the organic waste from the heavy metal discharge. This was done with a physical dam which diverted the waste streams into different trenches.
This allowed chrome waste water to be isolated for batch removal of the heavy metal through a process of chelation, followed with coagulation to remove soluble chrome to below 0.5 mg/l. The precipitated (or chelated) chrome was periodically removed from the settling basin for disposal.
The 0.05 mg/l chrome concentration was low enough to allow blending with the organic waste water stream, which was treated separately.
Earthen treatment equalization ponds were excavated and lined. Aeration equipment was designed and employed to biologically reduce the BOD/COD concentrations and to control odors. Specially selected and blended microbes were developed for this application.
After bacteria treatment, water discharged from the Teneria San Miguel tannery contained less than 0.03 mg/l chrome and was clear enough to see through a glass. Odors normally emanating from processing hides were no longer coming from the stagnant pools. The business received the approval of the local government and the minister of health to continue operation.
