March 2014, Vol. 26, No.3

Cost-effective application of peracetic acid for high-level disinfection  

A Florida facility considers several alternatives to satisfy permit requirements 

Betancourt feature 2 Freddy Betancourt, David Hagan, Leland Dicus, Chuck Mura, Vipin Pangasa, and Joseph Viciere

The City of Largo, Fla., took a new approach to disinfection at its Advanced Wastewater Reclamation Facility (AWWRF) to meet new consent order mandates. The consent order from the Florida Department of Environmental Protection required the city to lower dichlorobromomethane (DCBM) concentrations in its surface water discharge at the facility to below 22 μg/L, the numeric limit in the state of Florida. DCBM is formed when chlorine mixes with organic compounds in final effluent. 

Thus, a new approach for disinfection was needed. The filtered effluent, prior to disinfection, periodically exhibited an unusually low UV transmittance (UVT) — as low as 38% — typically during summer, when wet weather peak flows tend to increase  dissolved organic chemicals in effluent. The challenge was to find a cost-effective disinfection alternative to chlorine for an effluent with a low UVT. Read full article (login required) 


Smooth sailing with a smart startup plan  

Lessons learned when starting, testing, and optimizing MBR systems 

Maillard feature 3 Vince Maillard, Jason VerNooy, Kristi Perri, and Thor Young

Membrane bioreactor (MBR) technology, which consists of an activated sludge process and a membrane filtration system (MFS), offers several benefits that have led to its widespread application in municipal and industrial wastewater treatment. MBR technology allows for greater flexibility in design and operation, as it is compatible with a broad range of process configurations, physical layouts, influent characteristics, operating conditions, and control strategies. MBRs also are ideal to accommodate growth or meet increasingly stringent effluent requirements within a relatively small footprint. 

However, due to the unique nature of the MBR process, proper testing and operation are needed to avoid costly inefficiencies, underperformance, or even process failures. To document the effect of different strategies in bringing an MBR facility on-line, two municipal MBR facilities were studied during startup, testing, and initial operation. Ten valuable lessons were selected from these case studies that can be applied to other similar MBR projects. Read full article (login required) 


Operations Forum Features

 Out of sight, out of time 

A collaborative approach for emergency pipeline repair 

Barraco feature 1 Sam Barraco, Bill Tatum, Mike Querry, Bill R. Smith, and Rami Issa

The Trinity River Authority (TRA) of Texas provides water and wastewater treatment along the state’s Trinity River basin. TRA’s Central Regional Wastewater System (CRWS) facility provides wastewater collection and treatment services for 1.2 million people in 20 cities and the Dallas–Fort Worth Airport. 

CRWS has 8 km (5 mi) of in-facility drain lines that collect return flows from all across the facility, with a majority of the flow passing through a 1500- and 1800-mm (60- and 72-in.) pipe to the influent pump stations. CRWS was in the beginning stages of an assessment and rehabilitation program for the entire in-facility drain system when a construction-related exposure of a manhole upstream of the 1500-mm line exposed signs of severe corrosion in the manhole and adjoining pipe. A manned inspection revealed that the pipe was nearing collapse. As a result, TRA declared an emergency repair and immediately began the process to locate and approve emergency construction funds. Read full article (login required) 


Side by side 

Comparing oxidation ditch and membrane bioreactor processes in Hutchinson, Minn. 

Nevers feature 4 Edward Nevers and Brian Mehr

The City of Hutchinson, Minn., owns a water resource recovery facility (WRRF) with an average design flow of 13,853 m3/d (3.66 mgd). The facilities include a membrane bioreactor (MBR), which came online in 2009, operating in parallel to the facility’s original oxidation ditch activated sludge process.   

The configuration of this facility presents the unique opportunity to compare the characteristics of these two technologies operating in parallel and treating the same wastewater. Read full article (login required) 


A STEP above the rest? 

The City of Lacey, Wash., tweaks then retweaks its O&M program to find a balance between maintenance and cost 

Lacey feature 5 Bill Cagle, Terry Cargil, and Roger Dickinson
The City of Lacey, Wash., has operated a gravity sewer for decades with an understanding that customer satisfaction and low life-cycle costs are the result of a well-balanced operations and maintenance (O&M) program. Too little maintenance leads to premature equipment failure and dissatisfied customers. However, too much maintenance leads to high costs. An early adopter of septic tank effluent pumping (STEP) sewers, the city worked with its STEP equipment manufacturer to develop O&M protocols that provided a similar balance between maintenance and cost-effectiveness for STEP systems. Read full article (login required)