Digital control has brought major advances in wastewater treatment operator productivity and plant efficiency and performance. Control systems enhance measurement precision and reliably keep critical processes within tolerances even when unattended. Here are some recent innovations in digital technology for wastewater treatment operations.
Programmable controller
The SEL-2411 programmable automation controller from Schweitzer Engineering Laboratories Inc. is designed for mission-critical applications in harsh water and wastewater applications. Digital and analog I/O options and various communications protocols provide flexibility.
Users can customize the SEL-2411 with enclosures, preprogramming and numerous other options to meet specific applications. In addition to UL and Class I, Division 2 ratings, the SEL-2411 operates in a temperature range of -40 to +85 degrees C and withstands electrostatic shock up to 15 kV and vibration/shock up to 15 g.
The free, downloadable programming software enables users to program logic equations with a drag-and-drop expression builder or a text editor. The device replaces PLCs and RTUs in vital processes such as wells, lift stations, blowers, booster pumps and scum pits. Built-in voltage and current connections allow operators to monitor electrical quality and power consumption, and can be accessed by operators via the front-panel display or through a SCADA system. Other inputs can be used to monitor flow, intrusion, motor temperature or other process variables. 509/332-1890; www.selinc.com.
Level detector
The Opti-Float level detector by Cox Research is mercury- and lead-free and looks and operates like a conventional float switch except that it uses plastic fiber-optic cable instead of electric wires. The detector can be used to replace mercury floats, which are being banned by state legislation.
The floats can be used directly in hazardous areas and have been tested at more than one million operations, 10 to 20 times that of electrical float switches. Through plastic fiber-optic cable, it transmits a beam of light from an LED in a remote transceiver down to the float, where the beam makes and breaks depending on the tilt of the float. When the transceiver detects the presence or absence of light, it activates a relay in the transceiver, which can then operate other devices. Kits are available for retrofitting of existing control panels. 800/910-9109; www.coxresearch.com.
Hand-held data collection
LabLite LLC offers a hand-held data collection module used to record data in the field or around the treatment plant. The data is then uploaded to laboratory or plant software. The program requires a Pocket PC or handheld running Windows Mobile 2003 SE operating system or higher, Microsoft ActiveSync, a sync cable or cradle, and a PC with access to the SQL Server hosting the LabLite database.
Collection data used to populate the dropdown boxes are stored within the lab or plant software and downloaded to the handheld upon initialization. When a name is selected from the Users dropdown, the Site dropdown is populated. Sites assigned to the selected user appear at the top of the list, preceded by asterisks, followed by the remaining sites.
Matrix and Test dropdowns are populated in a similar manner. Once dropdown selections are made, Result and Bottle Number information can be entered. When the device is returned to its cradle, or connected via the synchronization cable, data can be uploaded to the database, and removed from the grid. 888/954-5483; www.lablite.com.
Control equipment service
Revere Control Systems’ aftermarket service program for digital control system equipment covers PLC software and hardware upgrades; programming for PLCs, HMI, DCS and SCADA; computer hardware and software upgrades; network security; site control systems inspection; loop tuning; circuit board exchange; calibration; wireless and fiber-optic work; and custom report gener-ation. Multiple service plans are available to fit different needs and budgets. Custom plans can be developed. 800/536-2525; www.reverecontrol.com.
Remote monitoring
The I-Link Lift Station Notifier (I-Link LSN 200) remote monitoring system by SJR-Rhombus is designed for monitoring pump lift stations and other pump applications. The next-generation system uses a Web-based gateway to collect and report system status and alarm events to a database application via a cellular phone modem.
The device can be installed in new control panels or retrofitted to existing systems. Two-way communication lets users monitor system performance and program system parameters from a PC. Reporting capabilities provide instant results — the system notifies users of a system event as it occurs, detailing complete event specifications.
Normal operating conditions are reported daily. Features include power fail detection, service button interface, high- and low-level alarm, and digital relay output. The device includes access to a secure, custom Web site to allow monitoring and administration of the unit and its data. The user-friendly Web page database displays time-stamped alarm events, mapping of locations, configurable alarm-handling options, historical data, and custom reporting. 218/847-1317; www.sjerhombus.com.
Ultrasonic level transmitter
MJK North America Inc. offers new software features for its digital ultrasonic Shuttle level transmitter. Software allows operators to switch to and use new sensor frequencies and types to optimize selections for their application needs. The software also has a higher-resolution false echo detection and screening of up to 22 separate echoes.
New signal management features include amplification filters and new solids level application setups. Advanced signal controls allow measurements from 0 to 4 inches through up to 75 feet with one sensor, while being less affected by foam, surface debris or out-of-range signals (spiking). It has simple alarm control, level control or alternating pump control with its two relays. The mA transmitter output is fully scalable. The device also operates either as a three-wire, loop-powered device or as a 115VAC powered device for installation flexibility. 877/655-5465; www.mjk.com.
Modbus-compatible modules
DGH Corp. offers the D3000M series of Modbus-compatible smart digital-to-analog modules that make it easy to control an analog output using a serial port. The modules combine a 12-bit DAC (digital-to-analog converter) with programmable analog-output control features and communicate using Modbus RTU over an RS-232C or RS-485 link. The series has 16 models: voltage (0-1V, +/- 1V, 0-5V, +/-5V, 0-10V, +/- 10Vdc), current (0-20mA, 4-20mA), with either RS-232 or RS-485 input.
Output slopes are fully programmable from 0.01V/s (mA/s) to 10,000V/s (mA/s). Input-to-output isolation is 500Vrms. Output burnout protection is 240VAC (current outputs), +/-30V (voltage models). The modules are packaged in a unique 3.60- by 2.45- by 0.85-inch ABS case with captive hardware and a plug-in screw terminal connector. 603/622-0452; www.dghcorp.com.
