Developing countries including Kenya, have recorded rapid growth in industrialization and population. This

growth has contributed to a rise in wastewater pollution, leading to serious environmental and health risks.

Paint and pigment manufacturing industries release heavy metals like lead, cadmium, and chromium into water

bodies. These heavy metals threaten aquatic life and human health. Traditional treatment methods are costly and

not widely used, creating a need for sustainable alternatives.This study examines the efficiency of coagulation,

flocculation, and adsorption in removing heavy metals from industrial wastewater. Waste tires were carbonised

at 700°C to yield activated carbon adsorbents. They were later cleaned and optimised. Coagulation-flocculation

with aluminium sulphate reduced turbidity by 45.73-55.26%, however it was insufficient for heavy metal

Environmental pollution

Rapid industrialization and population growth in developing nations, especially Kenya, have led to severe

environmental challenges [1]. This is mainly due to poor wastewater treatment. In Nairobi's industrial area,

factories discharge untreated wastewater directly into the Nairobi River [2]. As a result, neighbouring

communities face serious health risks. Contaminated water has been linked to outbreaks of waterborne diseases

[3], [4]. There is need for intervention.

Figure 1: Chart showing environmental challenges faced in Kenya.

The growing demand for decorative and automotive coatings has driven the paint industry. The demand has

control method.

Transforming old tyres into carbon-based materials is proving to be an effective way to filter out contaminants

from both industrial and household wastewater [7], [8], [5]. This approach showcases how innovative waste

management solutions can support long-term sustainability efforts.

Figure 2: Process of Transforming waste tyre into Activated Charcoal

Statement of the Problem

The release of wastewater containing heavy metals into Nairobi River is a major threat to both the environment

and public health [9] [10]. Traditional treatment methods are expensive and therefore not widely used [11]. It is

Specific Objectives

i. To determine the reduction efficiency of coagulation-flocculation in heavy metal removal.

ii. To investigate the adsorption capacity of activated carbon derived from waste tyres.

iii. To determine the optimal conditions for adsorption, including dosage, contact time, and pH.

Wastewater samples were collected from three paint factories located in the industrial area of Nairobi County.

The samples were collected and transported to the laboratory for analysis.

finely ground, and processed into a powdered form suitable for adsorption studies.

To determine the optimal adsorption conditions, different dosages of the adsorbent (ranging from 0.1 to 0.7 g)

were tested in wastewater samples. The contact time between the adsorbent and wastewater was varied between

30 and 120 minutes to assess its effect on metal removal efficiency. Additionally, the pH of the samples was

adjusted between 2 and 9 to identify the most favourable conditions for adsorption.

Figure 3: Image of samples prepared for Analysis

The residual heavy metal concentrations in the treated samples were analyzed using Atomic Absorption

Figure 3: Atomic Absorption Spectrometry instrument used for analysis.

The wastewater samples showed high levels of contamination, with COD ranging from 916.77 to 1881.20 mg/L,

BOD between 149.00 and 183.00 mg/L, and TSS from 6382.3 to 7395.33 mg/L. These values indicate significant

organic and inorganic pollution. The levels of COD, BOD, TSS, oil and grease, total phosphorus, and total

(NEMA), indicating severe organic and nutrient pollution.

Heavy metal concentrations were also elevated, with cadmium levels between 3.03 and 4.18 mg/L, lead ranging

limits, posing a serious risk to both the environment and human health.

Turbidity reduction improved as the coagulant dosage increased, with the optimal aluminium sulphate

concentration of 8–10 mg per 200 mL achieving a turbidity reduction of 45.73–55.26%.

Figure 4: Results showing correspondence of waste water turbidity with increase in coagulant volume.

However, coagulation alone was not sufficient to lower heavy metal concentrations to acceptable levels.

provided a better fit for the experimental data than the Freundlich isotherm. This suggests that heavy metal

This study confirms that waste tyres can be repurposed into effective adsorbents for removing heavy metals from

industrial wastewater. While coagulation-flocculation helps reduce turbidity, it is not enough to lower heavy

metal concentrations to safe levels. Adsorption using tyre-derived activated carbon offers a cost-effective and

sustainable alternative for further purification.

The results showed that adsorption performance depended on factors such as pH, contact time, and adsorbent

dosage, with the Langmuir isotherm model best describing the adsorption process. This suggests that heavy

metal removal occurred as a monolayer on a uniform surface, highlighting the efficiency of the adsorbent.

However, further improvements are needed to enhance adsorption capacity and ensure the treated water meets

environmental standards. Future research could explore ways to modify the adsorbent for better performance

and assess its long-term effectiveness in large-scale applications. Overall, this approach not only provides a

2. O. J, Y. A, and O. J., “Assessment of Selected Parameters for Industrial Effluents from Some Industrial