The effect of household waste compost and horse manure on physicochemical parameters and biodegradation of total hydrocarbons in sludge polluted by hydrocarbons discharged from an oil refinery in the Republic of Congo

This study aims at evaluating the effectiveness of organic amendments on the treatment of sludge polluted by petroleum hydrocarbons from a refinery in Congo. The experimental device included 10 mini treatment basins with three randomized replications. The experiment was based on a 365-day landfarming technique combining two organic materials (horse manure and compost) and a mixture of the two, added in proportions of 0.5%, 1% and 1.5%, and a control with no amendment. During treatment, samples were taken and physico-chemical analyses carried out using conventional methods. The results showed that the averages for pH, moisture, electrical conductivity, organic matter and C/N ratio ranged throughout the treatment period from 6.8 to 8.1, 8.5% to 20.3%, 108.46 to 442.88 µs/cm, 8.03% to 9.13% and 36.40 to 61.99 respectively. These physicochemical parameters are in accordance with the hydrocarbon biodegradation standards related to good microbial activity. The total hydrocarbon degradation rates ranged from 34.90 for the control and 74% for the HM+CP 1.5% treatment. Thus, the contribution of organic amendments significantly improved the degradation rate of total hydrocarbons in treated sludge.