Water Treatment Handout 1
Treating the Acid Mine Drainage
Your team’s mine has the following parameters:
Typical Raw AMD Characteristics and Water Quality Requirements for Rainbow Trout.
Raw AMD* Requirements for Rainbow Trout**
pH 2.5 - 5.5 6.0 - 8.5
Acidity, as CaCO3 10 - 2,000 mg/L
Alkalinity, as CaCO3 0 mg/L 10 - 400 mg/L
Iron, Fe 5 - 2,000 mg/L < 0.1 mg/L
Aluminum, Al 2 - 300+ mg/L < 0.01 mg/L
Manganese, Mn 2 - 200 mg/L < 1.0 mg/L
Calcium, Ca 500 - 4,000 mg/L < 160 mg/L
Sulfate, SO4 500 - 4,000+ mg/L < 850 mg/L
Total Dissolved Solids, TDS 300 - 3,000+ mg/L < 80 mg/L
* Skousen and Ziemkiewicz 1996.
** Meade 1989.
A simplified method for determining quantity of compound needed to neutralize AMD is to
estimate the amount of base needed based on acidity. Acidity, the capacity of water to neutralize
bases (Tchobanoglous and Schroeder 1989), can be determined using a simple titrimetic lab
1) Determine the # of moles of CaCO3 equivalent acidity (Macid):
Acidity (mg/L CaCO 3 ) Volume (L)
2) Use the neutralizing agent’s molecular weight to determine the mass of agent needed.
For CaCO3, Ca(OH)2, CaO, and Na2CO3 use the following equation:
M Molecular Weight
Mass of Neutralizi ng Agent (kg) acid
For NaOH and NH3, use the following equation:
M acid Molecular Weight 2
Mass of Neutralizi ng Agent (kg)
Molecular Weights of Commonly Used Neutralizing Agents.
Molecular Weight MW Factor
Common Name Chemical Compound
Limestone CaCO3 100 1
Hydrated Lime Ca(OH)2 74 0.74
Quick Lime CaO 56 0.56
Caustic Soda NaOH 40 0.8
Soda ash, briquettes Na2CO3 106 1.06
Ammonia NH3 17 0.34
(Skousen and Ziemkiewicz, 1996)
Another common way to estimate the quantity of neutralizing agent needed is to use flow (in
gpm) and acidity (mg/L as CaCO3). First, the acid load must be calculated:
Tons of Acid per year Flow (gpm) Acidity (mg/L as CaCO 3 ) 0.0022
In ideal conditions, with proper mixing, one can assume 1 ton of acid load can be neutralized by
1ton of limestone (CaCO3). However, if other neutralizing agents are used, the difference in
molecular weight must be accounted for, as follows:
Tons of Neutralizing Agent per year Ton of Acid per year MW Factor
+All of this information came from Skousen and Ziemkiewicz 1996.