August 2007, Vol. 19, No.8

Water Reuse

An evaluation of the technologies and their benefits
Lisa Sorgini

waterreuse.jpg Lisa Sorgini

Reuse is one of the most important issues in the global water industry today, and for good reason. As droughts and water resource issues become more widespread, water reuse is a necessity that has proven to be economically and environmentally beneficial. Water reuse conserves limited potable water supplies

by reusing treated wastewater for nonpotable uses, such as irrigation and industrial processes. Recycled water also can be used for direct and indirect potable use, such as aquifer recharge and reservoir augmentation.  Read full article (login required)  


No Rain, No Water, BIG Problem

Water reuse should ease water supply strain in Brisbane, Australia

norainnowwaterbigproblem.jpg Cindy Wallis–Lage, Scott Freeman, Mark Steichen, Jonathan Bates, Jonathan Pressdee, Ivor Peries, and John McEvoy

Brisbane, Queensland — a major city on Australia’s East Coast — is experiencing severe water shortages. Drastic changes are needed to ensure that the region will have ongoing water supplies.

The impending water shortage is the result of both an ongoing drought and dramatic population growth. About 70% of the drinking water for Brisbane and the surrounding area comes from the Mt. Crosby Water Treatment Plant, whose intake on the Brisbane River is supplied by water released from the Wivenhoe Dam reservoir. The reservoir water is collected from the surrounding watershed and the Somerset Dam upstream. After 7 years of low rainfall, the reservoir is less than 20% full and projected to drop to an extremely low level if not replenished by seasonal rainfall within 16 months.  Read full article (login required)  


Keeping It Simple 

In some instances, plants can achieve high-tech effluent with a low-tech system

keepingitsimple.jpg Linvil G. Rich and Graham W. Rich

Newly imposed effluent limits on municipal wastewater treatment plant discharges are rapidly driving up treatment costs. For many small and medium-size communities, these costs have been especially acute, as they replace relatively

low-tech systems, such as aerated lagoons, with more costly activated sludge systems. However, in many cases, low-tech systems can achieve effluent concentrations of biochemical oxygen demand (BOD), total suspended solids (TSS), and ammonia–nitrogen that closely approach effluent concentrations of a more costly high-tech system.  Read full article (login required)  


Operations Forum Features

The Nitty Gritty

Peak flows and light grit

nittygritty.jpg George Wilson, George Tchobanoglous, and Jimmie Griffiths

Last month’s article, “The Nitty Gritty: Grit Sampling and Analysis,” looked at the basic principles of how grit travels in collection systems and how it settles — or doesn’t — in the headworks. This installment delves deeper into grit’s behavior. Specifically, it will examine what happens with grit when high flows flush the collection system and evaluate the
effectiveness of removing grit from primary solids instead of at the headworks.  Read full article (login required)  


Listening to Levels 

Installing Radar Level Instruments in Anaerobic Digesters

listeningtolevels.jpg Phil Ackman and Thao Le

It isn’t always easy to find equipment that can accurately measure what’s going on in a treatment process, and especially in an anaerobic digester. Wastewater or residuals can clog and blind instruments. Foaming, surface agitation, and a methane environment can make level measurement particularly difficult.

Radar level instruments, however, represent a new technology with the potential to overcome these problems and provide accurate, reliable digester level readings. In everyday operations, however, do these instruments live up to their potential?

That is the question the Los Angeles County Sanitation Districts (LACSD) wished to answer when it tested a new radar level instrument designed to detect sludge or foam levels in its anaerobic digesters.  Read full article (login required)   


What Is the Public Really Thinking? 

Separating fact from assumption

whatisthepublicreallythinking.jpg Lesley S. Robin

Normally, customer input to a public utility is sporadic at best. Most public utility managers would be inclined to think that if it’s quiet out there, everything must be okay.

But what happens when a utility must begin a large construction project, implement a higher rate structure, or present a controversial water recycling program to the customers?

In almost all cases, vocal public opinion is negative. Policy-
makers and governing boards usually get concerned and want the manager to “do something” to allay the negative input and get back on course. Policy-makers frequently draw conclusions about what all the customers are thinking based on the statements of the vocal group, no matter the size or representation. The manager needs to be able to separate public opinion assumptions from facts and convey the reality to the policy- and decision-makers.  Read full article (login required)