Home > News > Environment
Monday October 21, 2013 MYT 12:00:00 AM
Monday October 21, 2013 MYT 8:09:49 AM
by natalie heng
Vast network: Some 16,000km of sewer lines criss-cross the country, transporting sewage from homes and buildings into treatment plants operated by Indah Water Konsortium. — YAP CHEE HONG/The Star
One man’s poop is a microbe’s champagne breakfast.
LIFE’S basic necessities are often taken for granted – whether it’s having a hot shower, catching up with the latest episode of Dexter, or taking your morning dump with a copy of the newspaper.
The average household pays about RM10 a month on water, between RM60 and RM100 for electricity, and RM8 for sewerage services. But how much do we actually know about the vast infrastructure that is supported by these modest billings?
Azzattulina Pawanchik sheds some light on what is perhaps Malaysia’s most under-appreciated public service: sewage treatment. She is head of communications at Indah Water Konsortium (IWK), which handles 1,749 Olympic-sized swimming pools’ worth of household effluent, every day. Some 19.44 million people rely on the company to treat about 4.4 million cubic meters of wastewater from our kitchens, bathrooms and toilets. The cost for these services is 27 sen a day per household.
Our journey begins in an air-conditioned room at the IWK treatment plant in Bandar Tun Razak, Kuala Lumpur, where Azzattulina explains the difference between septic tanks and connected systems. I can’t help wandering why it matters, but it does, for a number of practical reasons.
Firstly, if you can’t tell the difference, you may not be aware of your responsibilities, hence, putting yourself at risk of breaking the law. As of 2008, owners of any house hooked up to an individual septic tank system are required by law (Water Services Industry Act 2006) to carry out scheduled desludging of their septic tanks. If you don’t, the tanks will overflow. And if this happens, not only will you have to deal with a god-awful stink around your house, you could also be contaminating groundwater and rivers with sewage – a danger both to public health and the environment.
Backyard sewage treatment
The new housing estates of today are connected to centralised sewage systems. It’s mainly the older houses, or isolated bungalows, that tend to have individual septic tanks.
If you aren’t sure what system you have, Azzatullina has a tip: “Just check to see if you have two or more metal covers in your garden, usually built in sequence.” If you find them, what you have is an on-site, self-contained sewage treatment system. The whole point of an individual septic tank is that waste gets treated underground, literally, underneath your house.
After effluent passes through the sewage pipelines in your premises, it ends up in a chamber. There, a layer of scum forms as oils, grease and fats float on top, and anaerobic bacteria proceed to feast on raw sewage. This takes about 24 hours.
As the heavier solids and sediments settle down, the upper layer of water becomes less murky. When more wastewater enters the chamber, the clear water discharges through an overflow pipe into the next chamber, usually passing through a filter. It then flows free and a lot cleaner, out into the public drainage system. Over time, the solids in the first chamber build up. Hence, regular desludging – the removal of this accumulated slimy solid matter – is required.
If the septic tank gets too full, sewage retention time decreases, resulting in incomplete breakdown of sewage. Untreated and foul-smelling sludge then ends up being released into the drain.
“Homeowners need to keep track of when the last desludging took place,” explains Azzatullina. “It needs to be done once every two years.”
When a homeowners needs to desludge, all they have to do is call up a National Water Service Commission or IWK registered contractor. The desludging is covered by IWK’s quarterly billings, unless the premise is located outside the 87 local authorities under its purview (some states still rely on local authorities for their sewage treatment services).
Things are a lot easier when you have a connected sewerage system. Instead of the whole process taking place underneath your house, all household effluent is directed towards centralised sewage treatment plants via public sewer lines. IWK maintains around 16,000km of sewer lines and relies on mechanisation to make wastewater treatment faster and more efficient.
“In the old days, we used simple oxidation ponds, large bodies of water where we let nature handle the organic decomposition.”
This approach operates on a simple premise – all that is needed to break down sewage is naturally-occurring microbes found in our waste and water. The microbes use dissolved oxygen and algal photosynthesis to “feed” on organic material, breaking it down and releasing nutrients and carbon dioxide as byproducts, which in turn, are re-used by the algae. The whole process takes a few days.
Previously, five oxidation ponds at the IWK site in Bandar Tun Razak could handle waste from a population of 35,000. As the population grew, a better way to process the waste, on the same amount of space, was needed. Today, they do that through a sophisticated sewage treatment system – the sequential batch reactor.
The treatment plant serves a 1,000ha catchment area; so whenever someone in Desa Petaling, Taman Midah, Taman Mulia or Desa Tun Razak flushes their toilet, chances are the contents of their toilet bowl end up right underneath us.
In essence, the reactor is just a smart way of maximising use of space. Everything is mechanised, so the facility is more compact, and waste is processed a lot faster. It was built in 2006 and currently serves about 70,000 people.
The sequential batch reactor does exactly what it says on the tin. It treats wastewater in batches in a reaction chamber of microbes, which “chew” the solid waste into microscopic pieces. When the first batch in the sequence is done, a portion of the clean water is released into the river.
About 70% of this water is retained because it contains the microbes needed to feed on the next batch of wastewater. The new batch is effectively being mixed in with a super-rich microbe soup, and more microbes mean faster digestion.
Azzattulina says a fresh batch of effluent will take about seven days of microbe digestion time before the water is clean enough to be released into rivers.
“But when it’s mixed with water pre-loaded with microbes, the process takes just six hours.”
There are some mechanical gadgets to make the process run smoothly: giant blowers and aerators pump bubbles into the reactor, increasing the levels and distribution of oxygen in the effluent. Breathing microbes are desirable because they perform aerobic digestion, which is far more efficient than anaerobic digestion. .
“Just imagine your aquarium at home. It’s like that, but we don’t rear fish, we rear microbes.”
Water once more
You might be surprised at the level of water quality achieved through this type of treatment process – Azzattulina says it is comparable to standards required of normal tap water.
“The Department of Environment’s requirement for water discharged from sewage treatment plants is a biological oxygen demand (BOD) level of 50mg/l. Our normal sewage treatment plants (oxidation ponds, for example) emit water with a BOD of 25mg/l. But the sequenced batch reactor here in Bandar Tun Razak emits water that contains less than 2mg/l of BOD.”
The new technology is a lot more efficient than the old. For example, one reactor treats over three times the population number of five oxidation ponds, but only takes up half the space. However, it will take time to replace old sewage treatment plants with the new technology.
Aside from cleaner effluent, the reactors also make it possible to maximise use of the sludge that remains after the treatment process. It can be transformed into a soil-like material, via thickening agents and a drying process, and transported to an approved landfill. It can also be used as fertiliser.
“The municipal council of Port Dickson currently uses sludge and water from the local wastewater treatment plant to fertilise landscaping plants,” says Azzattulina.
Tags / Keywords:
Environment, Environment, IWK, sewage treatment
Copyright © 1995-2013 Star Publications (M) Bhd (Co No 10894-D)