Shakil Amin, PE, BCEE has experience in detailed water and wastewater treatment facilities design, pump station, sewer collection system, inflow and infiltration analysis, water distribution system, booster pump station, regulatory permitting, and facility startup. Mr. Amin has worked on process design, modeling, evaluation of wastewater treatment plant expansion and upgrades alternatives, odor control system, treatment process equipment evaluation and selection, effluent filtration, disinfection and hydraulic analysis

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The City of Perry is located in Taylor County, Florida. Currently, the City of Perry obtains source water from three supply wells. The City identified elevated disinfection-by-products (DBPs) in its distribution. The City began seeking to identify the exact source of the DBP precursors and ultimately identified source well No. 7 as having elevated levels of total organic carbon (TOC), a natural organic material which is a known DBP precursor.

Well No. 7 (1,400 GPM capacity) is treated at the City of Perry Water treatment Plant No. 2, a 1.95 million-gallon per day (MGD) plant.  The raw water from well No.7 also has elevated iron content and has been successfully treated for years at Plant No. 2 via a treatment train consisting of a cascade aerator, a detention tank, gravity (dual media) granular filters, a chlorine contact chamber, and a clearwell that houses the high service pumps.  The cascade aerator, detention basin, and granular media is used to treat the iron in the raw water via precipitation of the iron as iron oxide, which is subsequentially filtered out by the direct filtration system.  Due to the unique nature of the plant layout, a means of treating the water from well 7 for DBP precursors was not feasible prior to the filtration system.  This resulted in requiring treatment post filtration and offered a novel location in the treatment train to provide DBP and TOC treatment.  New components used to treat the DBP, and TOC consists of:

• THM removal system located in the clearwell of the existing facility
• GAC sorption system located downstream of the existing high service pumps
• New chlorine injection point located downstream of the GAC filters.

Key aspects of the project that will be discussed include:

• Selection of the GAC system – Chlorine dioxide and PAC was investigated along with GAC as a means to treat the water.
• Location of GAC in the treatment train – GAC was selected to be used downstream of the existing high service pumps primarily due to the layout and footprint of the plant. RSSCT bench tests were performed using varying strengths of chlorine to analyze how the GAC would react and perform at the selected location. Breakthrough curves were developed for TTHMs, HAA5s, and TOC at each dose of chlorine.
• Selection of THM removal System - To increase the useful life of the GAC the RSSCT bench tests were also tested with varying levels of TTHMs to simulate how the addition of a THM air stripping/aeration system would affect the GAC.  Breakthrough curves for TTHMs, HAA5s, and TOC were developed to include the THM removal process.  The THM removal system lowered the total amount of TTHM the GAC was required to remove so it was included to prolong the cycle between carbon exchange times.
• Design of the systems – BIM (Revit) was used to model the GAC and THM equipment as well as the existing plant structures and associated plant piping.
• Permitting the improvements – FDEP has accepted the design and engineering on the novel improvements and a full scale pilot is scheduled to allow for optimization of the plant and to satisfy that the new processes will reduce the DBPs in the system to acceptable levels.

The proposed improvements to the Perry water treatment Plant No. 2 are fully designed and permitted and are scheduled to go into construction in the beginning of 2023.