This archive report was first published on 19 December 2019.
December 19, 2019
By Paul Wafula
Our investigation into the Sabaki River's toxic flow began with a daunting task: finding the river's mouth. The journey was not without its challenges, including a drone crash into a polluted river and run-ins with difficult policemen guarding the Sh82 billion Thwake dam.
Despite these obstacles, our team persevered, collecting 49 samples from 10 strategic points along the river. These samples included water, sediments, fish, vegetables, crabs, and other aquatic animals.
The sampling points were carefully selected to represent the major anthropogenic activities along the river, including agricultural and industrial activities. Our team mapped the entire river, breaking it down into several blocks based on the intensity of human and industry activity.
From Kiambu County where the river starts, our team followed the river through Nairobi County to Machakos, Makueni, Taita Taveta, and Kilifi, until it empties into the Indian Ocean at Sabaki Bridge. The river changes its name along the way, emptying into Athi River, then Galana, before finally becoming Sabaki River.
Our team worked tirelessly to collect the samples, using a smartphone to record the exact GPS coordinates of every sampling point. We collected four water samples at each point to ensure the sample collection was watertight.
The samples were then transported to the University of Nairobi's Public Health, Pharmacology and Toxicology (PHPT) laboratories for analysis. The project's lead researcher, Prof James Mbaria, and Dr Nduhiu Gitahi, the Principal Technologist, worked together to analyze the samples.
The microbial water quality was analyzed within six hours of sampling, while physiochemical analysis was carried out after all the samples were obtained. Sediments and fish, where available, were also sampled for chemical analysis.
Our team tested for the presence of 12 different metals of toxicological importance, including mercury, chromium, arsenic, cadmium, lead, selenium, copper, zinc, manganese, aluminium, and barium. We used the Atomic Absorption Spectrophotometric method to analyze the metals, as well as the National Environment Management Authority standards.
Our study did not stop there. To determine the extent of the pollution, we conducted a third round of tests, checking for physical and chemical properties such as temperature, pH, total dissolved solids, nitrates, ammonia, total suspended solids, fluorine, sulphates, sodium, chloride, calcium, phenolics, and cyanide.
