Features

October 2006, Vol. 18, No.10

Evaluating Bioreactor Alternatives

For industrial treatment, performance requirements will dictate the ideal configuration 

IMG_1530RoanokeWTP Paul M. Sutton and A. Paul Tonga

Selecting the optimal process to treat organic or inorganic contaminants present in industrial wastewaters or other aqueous streams can be simplified through the use of a general framework, especially when site-specific conditions make reactor efficiency an important consideration. To illustrate such an approach, this article describes a case study involving the selection of a full-scale application of a fluidized-bed reactor (FBR) to treat groundwater contaminated with perchlorate. The ideal bioreactor configuration will operate efficiently while achieving the design performance objective. Conventional activated sludge systems, trickling filters, and other bioreactor systems typically designed for operation at lower volumetric removal rates often are selected for applications in which space constraints are not a consideration or other conditions render these technologies acceptable. In some cases, both situations apply.  Read full article .

 

When It Bubbles Over

Excessive foam is a symptom of unstable digester conditions

FoamingDigestera Neil Massart, Robert Bates, Blair Corning, and Gary Neun

 Excessive foaming is a serious problem that seems to be becoming more prevalent among anaerobic digesters throughout North America. Researchers attribute increased foaming to the rise in advanced biological treatment processes and corresponding changes in the quantity and characteristics of waste activated sludge (WAS). The real problem, however, is not the foaming but the unstable digester operations that cause it.All anaerobic digesters foam to some extent. Acceptable amounts of foam remain in the digester. Excessive foam, on the other hand, escapes the digester and plugs the gas-piping system. But foaming is controllable if operators have the time and resources to monitor the system. Their goal should be to minimize the factors that exacerbate foaming — not eliminate foaming altogether.  Read full article .

 

Utility 101

Training can be costly, but the right program can help utilities yield a considerable return on their education investment

Acid_River_2 Seth Yoskowitz and Peggy Umphres

In today’s economic climate, a utility needs to educate its workforce faster, cheaper, and more effectively than ever. According to a study by the American Society for Training and Development (Alexandria, Va.), direct costs for training at U.S. firms typically amount to 2% of payroll costs. In an economic downturn, education and training budgets usually are the first to be cut. Therefore, many training programs are underfunded, and management often sees education as an expense rather than an investment.

When utilities do invest in training programs, they typically take a reactive approach. The courses they offer are more likely to address known problems than anticipate future needs of the workforce or customer base.

Most utility managers understand that knowledge acquisition is central to the success of any organization, but find it challenging to put relevant and effective educational programs into practice. However, with some advance planning and strategic direction, utilities can implement a proactive education and training program that can yield substantial benefits in productivity, customer service, and profitability.  Read full article . 

 

Operations Forum Features

Control System Automation Made Simple

OF_ControlArtjpg Troy A. Hertog

Control and telemetry systems enable remote monitoring and control of process variables and system equipment. While such automation systems play an important role in the operations of modern water and wastewater treatment facilities, they add another level of complexity to system designs.

When upgrading or purchasing new equipment for a control and telemetry system, it is necessary to consider system dynamics, short- and long-term costs, electrical interfaces, system architecture, and personal computer (PC) compatibility. Ample consideration also should be given to such factors as the application, technology, supplier, sensors, telemetry media, basic requirements (local versus remote control and information), remote access capability, and historical information. Whatever control and telemetry system is selected, it should be easy and safe to operate, maintain, and service; expandable and open; and self-paying over time. Such systems should also be simple and reliable.  Read full article .

 

Alarm Management

Operators at a regional wastewater treatment plant develop a process to reduce nuisance alarms

OF_AlarmArtjpg Michael D. Johnson and William Hendrix Jr.

The Sacramento (Calif.) Regional Wastewater Treatment Plant is one of the few treatment facilities designed during the 1970s that incorporates fully automatic control. In June 2001, the plant received a process computer control system that provides extensive alarm capabilities. With more than 37,000 database points, the system enables operators to monitor nearly every aspect of the plant, its processes, and the performance and condition of its equipment. The system displays all alarms from plant processes and the computer system on operator alarm screens. However, this new alarm capability generated far more alarms than the system and operators could manage.

By assessing, designing, implementing, and optimizing, the plant resolved these alarm management issues. As a result, the district has reduced the treatment plant’s total number of alarms by at least 50%, virtually eliminated nuisance alarms, maintained the number of unacknowledged alarms at zero, and significantly improved early detection and prevention of discharge violations.  Read full article . 

 

State of Alarm

With proper technology, operators can monitor processes and equipment remotely and continuously

OF_StateArtjpg David L. Cooper II and Alvan Plymire

 As the typical wastewater treatment plant increases in size and complexity, operators face growing challenges as they try to supervise individual process components while simultaneously overseeing the entire treatment system. A distributed control system that monitors and controls the various components comprising a facility’s overall treatment process can assist operators with these tasks, provided that the distributed control system is designed with the needs of operators in mind.  Read full article .