W.K. Merriman Products and Services

BIOLOGICAL   DIGESTION

ALKALI COMPARISON FOR BIOLOGICAL TREATMENT

Caustic Soda - NaOH

  • pH Control - Risk of pH overshoot, potentially killing biosystem.
  • Buffering and Alkalinity - No buffering, alkalinity quickly depleted.
  • Nutrients - No nutrient value. Causes greatest increase in toxicity.
  • Scaling - Minimizes the potential for scaling in denitrification systems.
  • Phosphates - No effect on soluble phosphate concentrations.
  • Sulphates - No effect on soluble sulfate concentrations.
  • Hydrogen Sulfide - Lowest effect of any neutralizer on hydrogen sulfide.

Soda Ash - Na2CO3

  • pH Control - Risk of pH overshoot, overfeeding will cause biosystem damage.
  • Buffering and Alkalinity - Buffers well, but creates carbonate which precipitates excess hardness.
  • Nutrients - Precipitates hardness, helps maintain magnesium and calcium alkalinity in sludge.
  • Scaling - Adds excess carbonate. May cause scaling in denitrification systems.
  • Phosphates - No effect on soluble phosphate concentrations.
  • Sulphates - No effect on soluble sulfate concentrations.
  • Hydrogen Sulfide - May help reduce hydrogen sulfide concentrations in some systems.

Hydrated Lime - Ca(OH)2

  • pH Control - Risk of pH overshoot, overfeeding can cause biosystem damage.
  • Buffering and Alkalinity - Adds true alkalinity and stabilizes carbonate concentrations.
  • Nutrients - Adds calcium, essential for cell growth and energy storage.
  • Scaling - Excessive use can cause scaling in denitrification systems if operating at a high pH.
  • Phosphates - Greatest reduction of phosphate concentration.
  • Sulphates - Greatest reduction of soluble sulfate concentration.
  • Hydrogen Sulfide - Precipitates sulfates that might convert to hydrogen sulfide in anaerobic systems.

Dolomitic Lime - Ca·Mg(OH)4

  • pH Control - Risk of pH overshoot. Safer than hydrated lime, biosystem damage still possible.
  • Buffering and Alkalinity - Adds true alkalinity and moderate buffering while stabilizing carbonate hardness.
  • Nutrients - Adds calcium and magnesium, maximizing phosphate energy storage and healthy cell growth.
  • Scaling - Less potential for scaling than hydrated lime in denitrification systems.
  • Phosphates - Excellent at reducing soluble phosphate concentrations.
  • Sulphates - Excellent at reducing soluble sulfate concentrations.
  • Hydrogen Sulfide - Precipitates sulfates, moderates the production of hydrogen sulfide.

Magnesium Hydroxide - Mg(OH)2

  • pH Control - Will not overshoot pH. Will not damage biosystem.
  • Buffering and Alkalinity - Adds alkalinity that buffers well, excess alkalinity is recycled in biosolids.
  • Nutrients - Adds magnesium, a minor nutrient for proper cell growth.
  • Scaling - Minimizes the potential for scaling in denitrification systems.
  • Phosphates - Maintains soluble phosphate at optimum healthy levels in most systems.
  • Sulphates - No effect on soluble sulfate concentrations.
  • Hydrogen Sulfide - Inhibits the conversion of sulfates to hydrogen sulfide.