Aquatic Weed Cutting & Harvesting Success
Ninety-eight percent of Malawi’s electricity supply comes from five hydro plants on the Shire River. An increase in floating aquatic weeds and debris caused serious operational problems at the stations and resulted in millions of dollars spent on repairs. For example, the intake structures at one plant were so blocked by accumulated weeds, water could not pass through. This situation created a vacuum in the intake tunnel while the machines were running; the result was a collapse of the intake screens. Repairing the screens and returning the station to service cost more than $12 million.
After several years and a couple of failed weed management programs officials needed a better way to minimize the effect of aquatic weeds to hydro plant generation and restore the beauty of the Shire River at the same time. That “better way” involved a mechanical means to combat the weeds including an Aquarius Systems weed shredder (Swamp Devil™), a mechanical weed harvester, a shore conveyor, and a trailer conveyor.
The automatic vegetation shredder was immediately put into operation. This boat contains two blades at the front, which are used for both propulsion and as cutters. It chops aquatic weeds into pieces about 15 millimeters long. In addition to collecting weeds that have been chopped by the automatic vegetation cutter, the harvester can collect weeds that have not been chopped. Once the harvester is at capacity, it off-loads the weeds onto the shore conveyor and returns to work. In the mean time the shore conveyor transports the cut weeds to the unloading site on shore. Trucks then take the weeds to a designated depository site.
The success of the project can be measured on several levels. There have been virtually no plant shut downs after nearly three years running and the hydro station owners can operate its hydro facilities in an almost debris-free environment. This has allowed greater efficiency of the hydro stations and has improved the image of the company to its customers and stakeholders. The success is also measured by the social benefits in the nearby area. First, it has created jobs. The project employs a marine engineer and other marine technicians, in accordance with the national water machinery regulations. Second, depositing the weeds in farm fields is improving soil fertility. This allows local farmers to reduce their reliance on artificial fertilizers, which coincidentally is what provided the nutrients for the aquatic plants to grow and multiply to begin with.