KUALA LUMPUR: For once, here’s a little good news about the country’s beleaguered rivers.Last year, the number of rivers in the cleanest category was almost double that of 2005.The number of polluted river basins were also down by more than half.And as long as river clean-up and rehabilitation efforts are sustained, Malaysia can expect this happy trend to continue, says the Department of Environment.

Last year, only seven of Malaysia’s 146 river basins were categoried as polluted, down from 15 the year before.All the polluted river basins were in Peninsular Malaysia, with Johor topping the list.

Sungai Segget, Sungai Tebrau, Sungai Danga and Kawasan Pasir Gudang river basins in Johor are still in the polluted category as they were in previous years.Next are the infamous Sungai Juru and Sungai Pinang river basins in Penang, according to the Environment Quality Report 2006.

Selangor has just one, the Sungai Buloh river basin. The other eight river basins had moved on notch into the “slightly polluted” category. The report says that the Water Quality Index of the eight- Sungai Merbok. Sungai Bayan Lepas, Sungai Klang, Sungai Jejawi, Sungai Merlimau, Sungai Air baloi, Sungai Kempas and Sungai Sembulan- had improved.

For a long time, these and other rivers had been the subject of reports of worsening pollution, poor quality drinking water and examples of failed awareness programmes.The government had even set aside RM 200 million under the Ninth Malaysia Plan for river rehabilitation.

According to national standards, a river is classified from Class I to V, with Class I being the cleanest and Class V, the worst polluted.

The “class” of a river determines what it can be used for; whether for drinking, bathing, agriculture or nothing at all.

Last year, the DOE’s annual report on the state of the environment showed that there were 14 Class I rivers last year compared with eight in 2005. Water from such river can be supplied to consumers with practically no treatment and can also support the most sensitive aquatic species.However, five rivers that were in Class I in 2005 fell to Class II last year.

In this class, the river water would have to be conventionally treated before being distributed for consumption. A number of river within the eight basins that showed improvement moved up from Class IV to Class III.

In the Sungai Klang basin, for instance, all but one of its 11 rivers have been categorised as Class III, compared with six in 2005. Under National Water Quality Standards, a Class III river can be used to supply drinking water but only with extensive treatment. A Class IV river can only be used for registration. A Class V river is the worst and is termed a septic river.

Of the 146 basins monitored, there are two- Sungai Jelutong in Penang and Sungai Tukang Batu in Johor, says the report- which can’t be used for any purpose. In terms of sources of pollution, 42 basins were categorised as polluted by suspended solids last year- a marked increase from just 34 in 2005.

Suspended solids are mainly the result of earthworks and land clearing. Twenty- two basins were categorised as polluted by Biochemical Oxygen Demand (DOB) and 41 by ammoniacal nitrigen.

BOD is contributed largely by untreated or patially treated sewage, as well as agriculture and industrial discharge. The sources of ammoniacal nitrogen are domestic sewage and livestock farming.

Three rivers, Sungai Selangor, Sungai Terangganu and Sungai Melaka had recorded lower pH values, making them slightly acidic. A low pH is an indicator of low levels of dissolved oxyen in the river water, which could be hamful to aquatic life in the river if allowed to worsen.

Since the late 1970s, the DOE has measured the levels of many pollutants, including BOD and ammoniacal nitrogen , at hundreds of monitoring stations along rivers to determine their condition and classification.

The worst river will have the highest level of pollutants and the lowest level of dissolved oxygen. Dissolved oxygen is crucial to the survival of aquatic life and is one of the most important indicators of environmental health.

The status of a river basin is classified based on the averange pollutant readings from all the monitoring stations that are within it.