Case Studies

These case studies illustrate how Alcoa is acting upon its commitment to sustainable development throughout the world. We are pleased with this progress, but look forward to achieving even more.

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Wetland cell with cattails.

 

USA - 2011

Innovative Wastewater Treatment System Reduces Costs, Reuses Bauxite Residue


A wastewater treatment system developed and installed at the Alcoa Technical Center (ATC) outside Pittsburgh (USA) uses biology combined with bauxite residue—a byproduct of the alumina refining process—to treat up to 190 cubic meters (50,000 gallons) of wastewater each day. The chemical-free, environmentally friendly system reduced capital costs significantly, operating costs by 40%, and energy use by 30% compared to a conventional tank-based system.

 

The Natural Engineered Wastewater Treatment (NEWT) system replaced a tank-based, activated sludge system at the 51-hectare (127-acre) center, which is the largest light metals research facility in the world. Since June 2009, the NEWT system has treated 100% of the facility’s sanitary wastewater and maintained 100% compliance with all pollutant discharge permits (see chart below).

 

“The idea of the NEWT system is exciting to me because it appears to be a cost-effective method for dealing with wastewater issues,” said Jack Crislip, planning supervisor, Bureau of Water Management, Pennsylvania Department of Environmental Protection. “There are many smaller communities that find it difficult to replace malfunctioning septic tank type systems with conventional wastewater treatment systems because of the operational and maintenance costs. I’m encouraged that the NEWT system may be a viable alternative.”

 

The NEWT system treats wastewater through a series of low-energy, natural stages designed to remove a multitude of organic and pathogenic contaminants (see a graphic representation). It consists of the following:

  • Stage 1: Septic tanks provide primary treatment of the solid waste.
  • Stage 2: Definitive engineered wetland cells, designed with an external consultant, include cattails, which provide oxygen and take up nutrients; large stones that collect microorganisms, which break down waste matter; and a clay liner to protect subsurface groundwater.
  • Stage 3: Bauxite residue innovative treatment environment cells disinfect and polish the wastewater.
  • Stage 4: Treated water is discharged under permit into a nearby stream.

 

A key component of the technology is the treatment sequence, which provides for synergy among the various components for maximum removal of contaminants commonly found in sanitary wastewater. In the event the volume of water moving through the 0.6-hectare (1.5-acre) system exceeds capacity, such as after heavy rainfall, ATC has maintained chlorination capabilities to treat wastewater that may not meet permitted disinfection levels.

 

In addition to the capital, operational, and energy cost savings, the NEWT system provides for a more aesthetically pleasing and safer operation compared to traditional treatment systems that use extensive piping and chemicals.

 

Researchers and engineers at ATC are working to optimize the NEWT system with a focus on reducing its footprint to less than that of a conventional tank-based system; removing nutrients, such as nitrogen and phosphorus; and evaluating treatment of other wastewater, including process wastewater. ATC also is currently working to deploy this technology at other Alcoa locations worldwide.

 

“We would like to see this technology move from the private sector into the public sector so we can possibly get a lot of these smaller communities onto a wastewater treatment system that has low operational and maintenance costs,” said Crislip. “The use of bauxite residue as a disinfectant is also appealing due to the environmental and cost drawbacks of conventional disinfectants.”

 

In 2011, the NEWT system earned an Alcoa IMPACT Award for environment, health, and safety performance and sustainability.

 
ATC National Pollutant Discharge Elimination System (NPDES) Permit Limits
Permit Parameter
NPDES Monthly Average Limit
ATC NEWT Effluent Average
Carbonaceous Biochemical Oxygen Demand (CBOD-5) 25 mg/L 3.8 mg/L
Suspended Solids 30 mg/L 1.2 mg/L
Ammonia Nitrogen 2.0 mg/L (summer)
4.0 mg/L (winter)
0.1 mg/L
Dissolved Oxygen 5.0 mg/L min 7.8 mg/L
Fecal Coliform 200* colony forming unit (cfu)/100 mL (summer)
2,000* cfu/100 mL (winter)
22* cfu/100 mL
pH 6 minimum; 9 maximum 7.8
*Geometric mean