The Effect of the Middleboro Wastewater Treatment Plant on the Water Quality of the Nemasket River

Students studied the effect of the Middleboro Waste Treatment Plant on the water quality of the Nemasket River. Students sampled for DO, temperature, pH, nutrients and macroinvertebrates. Sampling sites included the reference site at Rte 105 and the impact site at Murdock Street in Middleboro, MA. A recovery site was not sampled due to distance and time constraints. Students toured the treatment plant and interviewed Mr. Joseph Ciaglo to learn how the plant operated. Students learned that orthophosphates are removed using ferric chloride to precipitate the phosphate. The analysis of samples for orthophosphate showed that the concentrations at Murdock Street were above normal range but below the concentration of Rte 105 on only one occasion. However, the concentration and load of nitrogen as nitrate was consistently higher at Murdock Street on each sampling date. The students learned that the treatment plant removes ammonia from the waste, not nitrate. Hence, total nitrogen reaching the water column meets NYPDES regulations for the plant, but nitrogen is still impacting the water quality.This impact can also be seen in the diversity of macroinvertebrates and in the Hilsenhoff 10-max Biotic Index. The HBI was 4.5 at Rte 105 indicating “good” water quality. Murdock Street had a value of 5.6 indicating “fair” water quality. The students concluded that even though the waste treatment plant meets NYPDES requirements, it still impacts the water quality of the Nemasket River.