The effects of carpet dye on the Bagmati River

Abstract

The objective of this thesis is to determine what, if any, significant effects effluent from the carpet dyeing industry has on the water quality of the Bagmati River in Kathmandu, Nepal. The water quality parameters studied were absorbance, as a color indicator, total chromium, dissolved oxygen (DO) and chemical oxygen demand (COD). Total chromium was measured both in samples from the Bagmati River and in dye samples. All four dyes tested contained chromium. Three of them contained high levels of chromium (1,200 - 2,400ppm). The highest level of chromium measured in any of the river samples was 0.03mg/L (found in two samples). This is below the World Health Organization's (WHO) guideline for chromium in drinking water, 0.05mg/L. This fact does not, however, necessarily indicate that there is not a chromium problem in the Bagmati River. Samples were collected and tested in January 2003, at which time carpet manufacturing was at a low. An increase in carpet production and subsequent increase of dye waste to the Bagmati River could increase chromium in the river to dangerous levels. There is a noticeable decrease in water quality as the Bagmati River flows through Kathmandu City. This water quality deterioration can be seen by looking at DO and COD levels along the river. Other researchers have theorized that dyes increase COD and therefore, may contribute to the high COD and low DO values in the Bagmati. However, in this study, dyes were not found to add a significant amount of COD.