The customer’s urban premises has two large ornamental ponds, and while they are ornamental, they have an area of 1400m2 and serve as stormwater collection and retention ponds before the stormwater is allowed to leave the site.
The ponds are concrete lined, with no obvious aquatic life present, however ducks do utilise the ponds. Sediment had accumulated on the base of the ponds, which varied in depth.
A significant amount of filamentous algae bloom is present, with algae growing out from the pond walls. This algae was also prolific throughout the water as it detached from the wall as part of its dispersion and procreation technique.
Once this algae is established it creates its own self supporting mechanism through continual seasonal blooms and die off. When the algae dies off in winter it creates a sediment blanket of nutrients that supports extra growth for the next season.
The floating and decaying filamentous algae produces an unpleasant smell, and provides an excellent habitat for mosquitoes and flying insects. When rainfall is reduced (summer months) the algae quickly depletes the water of dissolved oxygen leading to the water becoming stagnant and pungent in odour.
The algae has also blocked the pick-up of the fountain which reticulates the water, which further exacerbated the stagnation of the pond.