- The lake at Perdana Botanical Garden in Kuala Lumpur, after its rehabilitation, is safe for various water activities and family enjoyment
SINCE time immemorial, bodies of fresh water have drawn settlers to their shores and banks as a valuable natural resource necessary for survival.
Kuala Lumpur itself began on the confluence of two rivers — the Klang and Gombak rivers.
But as cities around the world began growing in both size and population, these lakes and rivers evolved into tranquil shelters from life’s hustle and bustle.
However, increasing development and indiscriminate rubbish dumping have resulted in pollution affecting these essential bodies of water, with some even turning into putrid, foul-smelling sites littered with waste or an overgrowth of aquatic plant life.
Kuala Lumpur City Hall (DBKL) started with the River of Life project in 2010 to transform and revive Klang River into an energetic waterfront hub brimming with activity.
It followed up with a project to rehabilitate the lakes through biologically friendly means within its jurisdiction.
Floating aerators were installed as part of the lake rehabilitation process to keep the usually stagnant lake waters circulating.
The initiative comes as part of DBKL’s undertaking for healthier lakes that support a rich biodiversity of aquatic life in a sustainable manner, said Kuala Lumpur mayor Datuk Seri Mohd Amin Nordin Abdul Aziz.
In addition to enhancing property value, the lakes are being rehabilitated for more functional purposes for the community.
Creating family-friendly environments that once again can be a centre of activity, these focal points will be made safe for activities such as birdwatching, kite-flying, water sports and boating.
As a historical green lung of the city since 1888, Perdana Botanical Gardens, also known as Lake Gardens, appropriately became the site for the first project.
Pollution of lakes
The Environment Department’s (DoE) water quality index classification ranges from Class I that indicates water safe for drinking to Class V, which is unsafe even for fishing.
Studies showed the Lake Gardens, approximately 4.85ha of water surface with a depth of 3m, was classified as Class III, Amin Nordin said.
“DBKL aimed to raise this to Class II, a level safe as a habitat for fish, skin contact and for recreational activities.
After the lake’s rehabilitation process at Perdana Botanical Garden’s, the area once again began attracting birds to roost as the lake became more habitable. — Photos: IRSYADI ISMAIL/ The Star
“We accomplished this after four months, through several stages of rehabilitation from April right up to August 2015,” he said.
The main contractor’s supplier Gilbert Ng provided the technical support for the lake rehabilitation project.
Ever wonder why the surface of lakes at times turns a shade of green or blue?
The blue or green is an unnatural eruption of growth in aquatic plants such as algae in the water body as a result of a process in which a high concentration of nutrients, commonly from artificial fertilisers, household waste or sewage, is introduced into a lake.
This process is called the eutrophication process and according to Ng, it is the main cause of water toxicity for many lakes in Kuala Lumpur.
“In the case of Lake Gardens, the pollution stemmed from surface run-off during heavy rains.
“This forms a sludge at the bottom of the lake that provides nutrients for aquatic plants such as blue-green algae to grow, becoming a layer over the surface of water like spilt paint.
“Water quality index is classified based on six parameters given by DoE, which we studied at the lake,” said Ng.
He explained that these included Ammoniacal Nitrogen, Biochemical Oxygen Demand, Chemical Oxygen Demand, oxygen content in the water known as Dissolved Oxygen, pH levels, and floating solids ot Total Suspended Solids.
Ng explained that the eutrophication process posed a problem for the fish, especially once the sun set as the algae stop producing oxygen but continued consuming the dissolved oxygen, which was essential for fish to breathe.
“Algae at a certain level is fine but if it is excessive, it starts to take up oxygen and compete with aquatic life in the lake,” he said.
Algae has a short lifespan, resulting in the increase of dead organic matter that also consumes the water body’s oxygen content as it decays.
Five interlinking steps went into rehabilitating the lake.
One of the priorities was to reduce fishkill count resulting from the water’s toxicity.
Therefore the first step was to increase the dissolved oxygen found in the lake.
Ng said, “The solution was by diffusing more dissolved oxygen into the lake, which we pumped in from the bottom of the lake in fine bubble form and continue to do so nightly.
“We also installed floating aerators that push floating sediment to the corners making it easier to collect manually.
“At the same time, this help circulate the water because lakes are stagnant, unlike rivers.”
According to Ng, functional microbes are also introduced into the lake.
“The anaerobic microbes we use compete with the algae for nutrients so the algae will not survive, at the same time without consuming oxygen in the lake,” he said.
In addition to these methods, a multi-frequency ultrasonic device is used to break down algae cell-structure.
A substance called bioflocculant is added and this acts as a glue to bind together the suspended solids and scum in the water making it easier to manually remove the floating sediment.
Aside from DBKL’s initiatives with the lake at Perdana Botanical Garden, Amin Nordin said the team was looking forward to rehabilitate the lakes in Intan Baiduri, Danau Kota, Ampang Hilir and Tasik Permaisuri.
The most challenging, however, will be the lake at Intan Baiduri as it is currently in the extreme Class III, verging on Class IV.
“This is because it also acts as a retention pond to mitigate flood waters, while waters from Selangor and Kuala Lumpur converge in the Intan Baiduri lake,” Ng pointed out.
The areas were chosen for restoration because of large number of visitors from the surrounding community.
Ng also said that frequent maintenance of lakes related to the different sources of pollution needed to be carried out.
Therefore, DBKL studies each lake before deciding on how to treat it on a case-to-case basis.
“Different environments result in different conditions depending on locations as some of the lakes were near hospitals, residential areas, drainage or sewage treatment plants,” Ng said.
Maintenance work will be on-going for the next 36 months with a unit to clean up and collect rubbish at the Perdana Botanical Gardens lake, seven days a week.
But as in all things, people play a part in the sustained success of these projects.