Features

September 2007, Vol. 19, No.9

Sustainability, One Project at a Time

A Pacific Northwest utility takes an incremental approach to managing capacity of its recycling, groundwater recharge, and marine discharge programs

sustainabilityoneproject.jpg Chris Cleveland, Karla Fowler, Bill McCarthy, and Brian Topolski

As a utility in one of the fastest-growing regions of Puget Sound, the LOTT (cities of Lacey, Olympia, and Tumwater; and Thurston County) Alliance has taken an innovative approach to sustainability: managing growth one chunk at a time. The utility’s Wastewater Resource Management Plan — now 8 years in place

— calls for LOTT to closely measure conditions and add capacity in “bite-sized” increments to match treatment and conveyance needs as closely as possible. The plan also marks a shift toward using wastewater as a resource, through reclaimed water and groundwater recharge. Although these methods have been used in dry climates for many years, they are new to the Pacific Northwest.  Read full article (login required)  

 

Reclaimed, Stored … Still Reusable?

Researchers evaluate reclaimed water changes during aquifer storage recovery operations

ReclaimedStored Still Reusable Rebecca Overacre, Tracy Clinton, David Pyne, Shane Snyder, and Peter Dillon

Aquifer storage recovery (ASR) is a type of groundwater recharge in which water is injected into an aquifer for
storage and later extracted via the same well. It is a powerful water-conservation tool, but its use — especially in reclaimed water programs — has not been fully explored. When reclaimed water is stored, there is uncertainty about its effect on native groundwater and its quality after storage. So, researchers conducted a 2-year study to observe water quality changes in reclaimed-water ASR operations at four test sites over various recharge and recovery periods.  Read full article (login required) 

 

That’s Enough Salt, Thanks

New method evaluates aquatic organisms’ ability to tolerate salinity

thatsenoughsalt.jpg Nikolay Voutchkov

 Seawater desalination has been gaining popularity as a freshwater production method in California, Florida, Texas, and Georgia during the last 5 years. However, one prevalent concern about desalination is the effect of its high-salinity effluent on aquatic life.

Seawater desalination plants use 1.5 to 2.5 m3 of seawater to produce 1 m3 of fresh water. Their main byproduct is a high-salinity stream (called concentrate or brine) whose volume is similar to that of the fresh water produced and whose total dissolved solids (TDS) concentration is 1.5 to 2.5 times higher than that of seawater. Because of its high salinity and negative buoyancy, this concentrate must be either blended with another discharge (such as power plant cooling water or wastewater effluent) or discharged via a diffuser system that will rapidly mix the concentrate with the ambient seawater and thereby mitigate its effect on the aquatic environment.  Read full article (login required) 

 

Operations Forum Features

Survival Without Bypass

Stormwater management for BNR facilities

survivalwithoutbypass.jpg Baneeta Sabherwal, Ed Kobylinski, John Keller, Mike Lawrence, and Robert Moore

Most wastewater treatment plants are designed to treat at least twice their average flows, but it is not uncommon for facilities to receive flows more than four times the average. Permit limits are becoming
increasingly strict, and there is no room for any type of process upset. Although adopting a relatively conservative design is an option, it may not be the most cost-effective way to manage the additional flow generated during storm events.

The performance of a biological treatment system depends on the ability of the secondary clarifiers to handle peak flows. Increased flows through the aeration basins result in increased solids loading rates to the secondary clarifiers, potentially leading to solids washout and permit violations. It is often difficult for shallow clarifiers to contain the typical low-density activated sludge solids during high hydraulic-loading events. Those facilities that get to bypass excessive wet weather flows have a much easier time than the facilities that must pass all wet weather flows through secondary treatment.  Read full article (login required)  

 

For Good Measure

Breaking down turbidity and total suspended solids

forgoodmeasure.jpg Marcus Allhands

 When two distinct physical parameters are used interchangeably, an intimate understanding of both is in order to know if and when this is justifiable. Two such parameters are turbidity and total suspended solids (TSS). In many industries, the concentration of TSS is of utmost importance to quality control and process optimization.
However, turbidity is often used as a surrogate for TSS.

In most cases, turbidity is measured simply because of convenience. In many applications, an empirical relationship between turbidity measurements and TSS values can be determined within acceptable limits. Other times, there is no relationship, nor can one be inferred.  Read full article (login required)