Abstract:
Although waste from coffee processing is a
valuable resource to make biogas, compost, and
nutrient-rich animal food, it is usually dumped into
nearby water courses. We carried out water quality
assessment at 44 sampling sites along 18 rivers that
receive untreated waste from 23 coffee pulping and
processing plants in Jimma Zone, Ethiopia. Twenty
upstream sampling sites free from coffee waste impact
served as control, and 24 downstream sampling sites
affected by coffee waste were selected for comparison.
Physicochemical and biological results revealed a significant river water quality deterioration as a result of
disposing untreated coffee waste into running water
courses. During coffee-processing (wet) season, the
highest organic load (1,900 mg/l), measured as biochemical oxygen demand, depleted dissolved oxygen
(DO) to a level less than 0.01 mg/l, and thus curtailed
nitrification. During off season, oxygen started to recuperate and augmented nitrification. The shift from
significantly elevated organic load and reduced DO in
the wet season to increased nitrate in the off season
was found to be the determining factor for the difference
in macroinvertebrate community structure as verified by
ordination analysis. Macroinvertebrate diversity was
significantly reduced in impacted sites during the wet
season contrary to the off season. However, there was a
significant difference in the ratio of sensitive to
pollution-tolerant taxa in the off season, which remained
