What safety concerns may be present in the preliminary treatment process?
A. Hydrogen sulfide
B. Waterborne diseases
C. Physical accidents/hazards
D. Explosive mixtures/gases
Answer: A, B, C and D. The preliminary treatment area is one of the most hazardous in the treatment plant. Hydrogen sulfide and explosive gases such as methane are very possible due to long runs in collections systems and organisms consuming dissolved oxygen. Waterborne diseases are an everyday hazard in the industry. Personal hygiene and laundering work clothing (separate from all other home laundry) are key ways to avoid these diseases. Finally, physical accidents are always possible due to wet conditions, mechanical equipment, spills and electrical hazards. More information may be found in the California State University, Sacramento textbook: Operation of Wastewater Treatment Plants, volume one, eighth edition, Chapter 3.
DRINKING WATER
By Drew Hoelscher
What is an operator measuring when titrating sulfuric acid into a sample of water and stopping at a pH of 8.3?
A. Total alkalinity
B. Carbonate alkalinity
C. Bicarbonate alkalinity
D. Total hydroxide and one-half the carbonate alkalinity
Answer: D. To measure the alkalinity in raw and treated water at a drinking water plant, the operator typically collects a 50 mL or 100 mL water sample and adds phenolphthalein indicator. If the pH of the sample is above 8.3, the water will turn pink. The operator will decrease the pH to 8.3 by titrating sulfuric acid into the sample. At this time, the operator makes note of the milliliters of sulfuric acid used to determine the P alkalinity. The P alkalinity is the measure of the total hydroxide and one-half the carbonate alkalinity. The operator then determines the total alkalinity by adding another indicator and titrating with sulfuric acid until the correct pH end point has been reached.
About the authors
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.
