June 2009, Vol. 21, No.6

How Low Is Too Low?

Several years of low-dissolved-oxygen operations improve effluent quality

howlowistoolow.jpg Ronald G. Schuyler, Joseph R. Tamburini, Steve Hogg, and Rick Staggs

After taking on additional organic waste from local industries, the Fresno–Clovis Regional Wastewater Reclamation Facility found it difficult to meet requirements for effluent total suspended solids and  biochemical oxygen demand. The plant operations staff embarked on a radical — but ultimately successful — approach: Use a low dissolved-oxygen concentration in the aeration tanks. Data show that, even though hydraulic and organic loads increased, low-DO operation has been successful in improving both settleability and effluent quality for the last several years.    Read full article (login required)  .


Limited Public Funds?

How an Oregon utility is taking a new approach to meet economic challenges 

limitedpublicfunds.jpg Mark Poling, Nate Cullen, David Green, and Norman Pearson

It takes a concerted effort to make effective use of limited public funds during an economic downturn. Current economic challenges are changing the municipal bond market, the rate of customer growth is declining, and it is  increasingly difficult to collect revenue. It is no wonder that some utilities are considering changing their financial plans.Clean Water Services (CWS; Hillsboro, Ore.) is taking a new approach to its decision-making process for facilities planning and other alternative analysis studies. CWS is using three tools that systematically consider both financial and nonfinancial factors during planning or evaluations, increasing the probability of options that will minimize cost and maximize contribution to stakeholder value.    Read full article (login required)  


Viable Alternative

 Fine-tuning dewatering performance at North America’s largest municipal biosolids screw-press facility

viablealternative.jpg Kevin A. Kennedy and Richard Gilliam

The Monterey (Calif.) Regional Water Pollution Control Agency recently installed an 18-dry-Mg/d (20-dry-ton/d) screw-press dewatering system. This installation, which has been used for routine biosolids dewatering since November 2007, is the largest municipal biosolids screw-press dewatering system in North America.   Read full article (login required)  


Operations Forum Features

Taming Wild Sewer Systems

Municipalities using microbial addition in the collection system to improve economics of wastewater treatment

tamingwildsewersystems.jpg Rich Schici

Sewers are wild places. All types of naturally occurring bacteria grow there. The one thing these bacteria have in common is that, for the most part, they cause problems. Filamentous bacteria — specifically sulfate-reducing bacteria — produce hydrogen sulfide, and other odor  causing bacteria dominate the wild microbiology of the collection system.

In fact, the indigenous microbiological growth within the collection system is generally considered detrimental to treatment objectives when it reaches wastewater treatment plants (WWTPs). Long hours of retention time in the collection system can produce situations that hinder treatment. Long retention times also can cause corrosion and odor problems.

But what if the sewers could be tamed? What if those miles of existing pipe could be turned into a meaningful treatment step?   Read full article (login required)  


Bacterial Balance

 Florida city increases water reuse with biologically enhanced solids settling

bacterialbalance.jpg Christopher Hyde

In Florida, a state that leads the nation in water reuse, the city of Apopka, located near Orlando, is in a class by itself. Its 4.5-mgd (17,000-m3/d) wastewater treatment plant (WWTP), which treats an average flow of 2.6 mgd (9840 m3/d), won the David W. York Water Reuse Award in 1997. Since that time, the plant has more than doubled the amount of reuse water supplied to golf courses, recreation facilities, agricultural  irrigation, and more than 4000 residents, according to water resources manager Kevin Burgess.“In 1997, we provided 3.2 mgd [12,100 m3/d],” Burgess said. “Now the figure is 6.4 mgd [24,200 m3/d], including supplementation with groundwater.”

But 2 years ago, the plant faced an infestation of filamentous bacteria, including Nocardia, which led to poor solids settling. Burgess attributes the plant’s bounce back and continued success to using bioaugmentation to control the filamentous bacteria and improve solids settling.   Read full article (login required)