WASTEWATER

By Rick Lallish

Anhydrous or quicklime is great for pH-adjusting and coagulating solids. What must be done before it can be used?

A. It has to be properly mixed with a polymeric flocculant.

B. It must be slaked (mixed with water).

C. It has to be stored under a heating source if the temperature falls below 30 degrees F.

D. It has to be agglomerated with a mixing compound.

Answer: B. Quicklime is an excellent chemical for solids coagulation and pH adjustment. It is relatively inexpensive and easy to use. The main disadvantage is that it is difficult to store since it absorbs moisture and cakes solid. It also must be slaked (mixed into a slurry with water) before use. Upon use, you must take precautions as the slurry will heat and may reach boiling temperature quickly. Lime is also very irritating to the skin, eyes, lungs and mucous membranes, so proper PPE is recommended. More information may be found in the OWP, CSU-Sacramento textbook: Advanced Waste Treatment (Fifth Edition), Chapter 4.

DRINKING WATER

By Drew Hoelscher

How does a venturi meter measure flow?

A. The velocity of water causes a propeller or turbine to rotate.

B. Uses the voltage created between two electrodes as the water passes through.

C. Measures the difference in pressure from two separate points.

D. An electronic transducer measures the velocity of a sound wave and translates to flow volume.

Answer: C. The venturi meter is a pressure-differential meter consisting of a converging cone, throat and diverging cone. The water flows faster as it exits the converging cone and enters the throat. The faster-moving water has a lower pressure than the slower-moving water upstream of the converging cone. The difference in pressure at these two points is translated into a volume of flow.

About the author

Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville.