Sains Malaysiana 40(8)(2011): 821–825

Effects of Thermal Stratification on the Concentration of Iron and Manganese in a Tropical Water Supply Reservoir

(Kesan Perlintapan Haba ke atas Kepekatan Ferum dan Mangan di dalam Takungan Air Bekalan Tropika)

Noor Halini Baharim*

Faculty of Science and Environmental Technology, Universiti Industri Selangor, Jalan Timur Tambahan

45600 Bestari Jaya, Selangor, Malaysia

Razali Ismail

Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia

Mohamad Hanif Omar

Jabatan Kimia Malaysia, 46100 Petaling Jaya, Selangor, Malaysia

Received: 10 May 2010 / Accepted: 22 December 2010

ABSTRACT

Thermal stratification in lakes is an important natural process that can have a significant effect on the water resource quality. The potential changes in chemical contents in water resulting from stratification are the production of ammonia, sulphides and algal nutrients and the increasing concentrations of iron and manganese. One of the water supply reservoirs located in Johor, Malaysia facing with high iron and manganese concentrations associated with the period of stratifications. This study showed that the level of thermal stratification in the reservoir varied at different time of the year. During the strongest period of stratification, the dissolved oxygen content was found to diminish significantly with depth and iron and manganese were recorded at the highest concentrations. Although significant period of rainfalls contributed to the natural destratification of reservoir, lower concentrations of iron and manganese only remained for a shorter period before the concentrations continued to increase with the onset of the thermal stratification. A good understanding on the behaviour of the reservoir may help to identify several measures for the improvement of water quality.

Keywords: Iron; manganese; thermal stratification; water quality

ABSTRAK

Perlintapan haba yang berlaku di dalam tasik merupakan suatu proses semula jadi yang memainkan peranan penting terhadap kualiti air bekalan. Antara perubahan kimia yang berlaku di dalam air hasil daripada perlintapan haba adalah penghasilan ammonia, ion sulfida dan nutrisi alga serta peningkatan kepekatan ferum dan mangan. Sebuah tasik takungan tropika yang membekalkan air mentah kepada loji air minuman di Johor, Malaysia menghadapi masalah kepekatan ferum dan mangan yang tinggi disebabkan oleh perlintapan yang berlaku. Kajian ini menunjukkan tahap kewujudan perlintapan haba dalam tasik takungan tropika berubah-ubah sepanjang tahun. Pada tahap perlintapan haba yang tinggi, kandungan oksigen terlarut berkurangan mengikut kedalaman tasik menyebabkan kepekatan yang tinggi bagi ferum dan mangan. Walaupun musim hujan mempengaruhi penyahlintapan haba secara semula jadi di dalam tasik, bacaan kepekatan ferum dan mangan yang rendah hanya mampu bertahan dalam tempoh masa yang pendek dan akan kembali meningkat apabila perlintapan berlaku semula. Pemahaman yang baik terhadap keadaan tasik takungan tropika ini dapat digunakan untuk mengenalpasti beberapa kaedah yang boleh diambil bagi tujuan peningkatan kualiti air.

Kata kunci: Ferum; kualiti air; mangan; perlintapan haba

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*Corresponding author; email: halini@unisel.edu.my