Dredge automatically excavates pond sediment at power plant

Oct. 1, 2006
Liquid Waste Technology's Pit Hog dredge removes sediment at the Enel Latin America power plant water supply in Zunil, Guatemala.

Liquid Waste Technology’s Pit Hog dredge removes sediment at the Enel Latin America power plant water supply in Zunil, Guatemala.

John Krahling

The global renewable energy company Enel Latin America needed to remove accumulating sediment in its power generation water supply at its Greenfield El Canada Power Plant in western Guatemala at Zunil. So the company asked the US company Liquid Waste Technology, LLC to design a LWT Pit Hog™ dredge equipped to automatically excavate the main pond’s sediment from the Santa Maria River.

The LWT dredge was specifically engineered to excavate the main pond’s sediment from the Santa Maria River while maintaining optimum production levels. This project is Enel’s second in Guatemala and is expected to contribute 178,000 Mwh to the national electricity system each year. Enel Latin America develops and operates renewable energy power plants in Central America.

LWT and company representative Felix Montes of Femco S.A. in Guatemala worked closely with the Enel Latin America engineering team to design, manufacture, and install an automated dredging operation. Enel’s engineering team of General Manager Ing. Juan Carlos and Plant Manager Florencio Gramajo visited the LWT plant in order to specify the correct controls, capabilities, and specifications to remove the sediment material effectively and at minimum cost.

Dredge being set-up at the Greenfield El Canada Power Plant in western Guatemala at Zunil

Gramajo said after the initial installation: “We have been able to keep the pond’s sediment at the same level with the LWT dredge; even when the rainy season is at the highest.” Michael Young, LWT’s service manager reported: "While the inflow from the river and the amount of material already present made the job difficult, the operators were operating the dredge efficiently within a couple of days." Officials of Enel Latin America were surprised at the high density of the pumped material. The discharge was much thicker than they had expected, according to LWT Service Technician Fred Hoffman.

Operators can control all dredge functions remotely from onshore or on-board the dredge. An Allen Bradley Panel View 600 Operator Interface at both locations coordinates various functions and controls. A LWT radio system provides the link from dredge to shore.

Liquid Waste Technology is the world leader in designing remote controlled dredging systems. Its remote controlled systems can be operated via multiple methods, including handheld radio remote control transmitters and fixed shore-mounted control panels. The LWT Pit Hog dredge removes sediments from reservoirs, settling lagoons, and wastewater treatment ponds. The Pit Hog excavates and transports these settled solids as slurry through a piping system to a pre-determined location.

Low-voltage electronic controls on the dredge make possible totally automated and remote operations. LWT programs a programmable logic controller (PLC) to provide control over the dredge’s automated functions and control loops, minimizing labor and maximizing production of solids at the set flow rate. This system is ideally suited for providing material to both dewatering and continuous process systems. The company supplies components and provides customized operational features to meet specific operational needs of projects.

Dredge control panel programmed on-site using an Allen Bradley Panel View 600 Operator Interface

Heavy-duty steel pontoons provide the necessary flotation to support on-board machinery and equipment in the water body. Principal features include the auger (excavator) head, submersible slurry pump, boom, boom hoist, traverse winch, electrical controls, and hydraulic system.

The functions of the auger head and the submersible slurry pump are essential for effective solids removal. The boom hoist positions the auger and submersible slurry pump vertically in the sediment while the traversing winch propels the machine forward and backward along a wire rope cable anchored at both ends (on both sides of the lagoon.) This design provides a cost effective means of hydraulically dredging sediments.

The system uses a LWT-designed rail-type lateral move system for positioning and anchoring the winch traverse wire rope. Generally, the system is comprised of two parallel rails located on opposite ends of the pond with the traverse cable stretched between them. The traverse cable is threaded through the treble sheave winch and cable guides on the dredge, which propels the dredge forward and backward. After the floating discharge hose and/or pipe are connected to the dredge, it is ready to operate.

Author’s Note

John Krahling is a sales engineer of Liquid Waste Technology, LLC, based in Somerset, Wisconsin, USA. LWT designs and manufactures sludge handling equipment, including auger dredges, lagoon pumpers, and submersible chopper pumps. For more information, visit: www.lwtpithog.com.