AWWA MTC57646

The New York City Department of Environmental Protection is in the preliminary designstage of a new 7 to 9 million gallon per day (MGD) drinking water plant. This plant willbe located in the borough of Queens and will utilize groundwater from the Upper GlacialAquifer (approximately 80-foot deep aquifer) as its sourcewater. The water has highlevels of iron (Total: 1 to 15 mg/l), manganese (1 to 1.5 mg/l), tetrachloroethene (PCE - 5to 160 ug/l), MTBE (1 to 140 ug/l), and hardness (150 to 600 mg/l as CaCO3). Theproposed full-scale treatment train for this plant includes pH adjustment, iron/manganeseoxidation, membrane filtration, membrane softening, two-stage air stripping, and finalchemical conditioning.As only the groundwater wells but no treatment plant currently exists on the site, a 100-gpm pilot plant was constructed within an empty storage building. The pilot plantprocess train includes parallel trains of pH adjustment via induced draft tray aerator orcaustic soda addition, parallel trains of iron and manganese oxidation by potassiumpermanganate or ozone, parallel trains of microfiltration (MF) and ultrafiltration (UF)skids (Ionics, Pall, & Zenon are manufacturers), and membrane softening (one Osmonicsskid will alternately test Koch nanofiltration (NF) and Osmonics low-pressure reverseosmosis (RO) membranes).Once a suitable pH-oxidation strategy was conceived and run through the MF/UF filters,the NF and RO membranes were put to the test to remove hardness and VOCs. One ofthe stated goals of the pilot plant was to evaluate the effectiveness of NF and ROmembranes to remove hardness and VOCs from the groundwater. Two NF/ROmembranes were alternately tested: Koch's NF and Osmonics' low-pressure ROmembranes, each for a continuous period of at least three weeks.New York City's upstate water supply (Catskill-Delaware systems) satisfies more than90% of the City's drinking water needs. This sourcewater is relatively soft (averagehardness of 22 mg/l as CaCO3); therefore, the City desired that groundwater from this newplant would closely resemble the water which the end users currently received. Withhigh hardness levels present in the Upper Glacial Aquifer, the NF and RO membraneswere tasked with this responsibility.In addition to hardness removal, it was also hoped that the NF and RO membranes couldremove some of the volatile organic compounds (VOCs) present in the groundwater. TheNF and RO membranes' ability to remove VOCs such as MTBE, PCE, and TCE isimportant in evaluating design objectives for a full-scale facility. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

03/05/2003

Number of Pages:

7

File Size:

1 file , 190 KB