# Water Treatment Handout 1

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```					                                 Water Treatment Handout 1
Treating the Acid Mine Drainage

Your team’s mine has the following parameters:
pH:_____
Temperature (Celsius):________
Flow (gallons/minute):_______
Acidity (mg/L):________

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
3+
Iron, Fe                             5 - 2,000 mg/L                      < 0.1 mg/L
3+
Aluminum, Al                          2 - 300+ mg/L                     < 0.01 mg/L
2+
Manganese, Mn                         2 - 200 mg/L                       < 1.0 mg/L
2+
Calcium, Ca                         500 - 4,000 mg/L                    < 160 mg/L
2-
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.

AMD Calculations
Method #1:
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
procedure.
1) Determine the # of moles of CaCO3 equivalent acidity (Macid):

Acidity (mg/L CaCO 3 )  Volume (L)
M acid 
100 ,000
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
1,000

For NaOH and NH3, use the following equation:
M acid  Molecular Weight  2
Mass of Neutralizi ng Agent (kg) 
1,000

Molecular Weights of Commonly Used Neutralizing Agents.
Neutralizing Agent
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)

Method #2:
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.

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