NC Phase W case studies
NC Phase W · Put your knowledge to work in context.
NC Phase W is a water and wastewater operator certification exam phase covering four domains: Water Treatment (30%), Water Distribution (30%), Wastewater Collection (20%), and Wastewater Treatment (20%). It is aimed at operators moving through the phased North Carolina operator certification ladder, and at candidates who need combined drinking water and wastewater knowledge rather than a single-discipline exam. The NC Phase W case studies are 5 cases and about 4,930 words.
1Filter Runs Collapse After a Storm at a 6-MGD Conventional Plant
Your 6-MGD conventional surface-water plant (two 3-MGD trains) draws from a Piedmont river. For ten days after a 2.5-inch storm, raw turbidity has run 18-30 NTU (normal 4-8 NTU), raw alkalinity has fallen from 42 to 30 mg/L as CaCO3, and raw TOC has risen from 3.1 to 5.4 mg/L.
937 words, about 5 min2Nitrite and Ammonia at a Dead-End Sample Station in a Chloraminated Zone
Your 3.2-MGD system switched to chloramines two years ago to control TTHM. Chlorine and ammonia are fed at the plant to a target of 0.9 mg/L total chlorine leaving the clearwell.
977 words, about 5 min3Lift Station 7 Rising Fast During a Night Storm
Station 7 serves 1,900 connections at the low end of a 12-inch gravity trunk. The station has two 450-gpm pumps in a lead/lag arrangement with automatic alternation; only one pump runs at a time.
1,028 words, about 5 min4Bulking Sludge, Low DO, and a Septage Station at a 0.8-MGD Plant
Your 0.8-MGD extended-aeration plant has two 0.25-MG aeration tanks and two 60-foot-diameter clarifiers with 10-foot side water depth. Permit limits are 30 mg/L TSS, 25 mg/L CBOD5, and 2.0 mg/L ammonia (May-October).
969 words, about 5 min5Lead Action Level Exceedance After a Free Chlorine Conversion
Your 1,100-connection groundwater system has three wells, free chlorination with gas, pH 7.3, alkalinity 40 mg/L as CaCO3, hardness 85 mg/L, and no corrosion inhibitor feed. The distribution system includes roughly 90 lead goosenecks and lead service lines on the older streets.
1,019 words, about 5 min