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A chromium-reducing strain isolated from activated sludge and subsequently identified as Clostridium sp. SS1 by a biomolecular method was studied for its resistance to toxic hexavalent chromium [Cr(VI)] and its ability to reduce Cr(IV). The strain was found to tolerate concentrations of Cr(VI) up to 50 mg/l; however, cell growth was severely affected by the presence of Cr(VI), especially at concentrations of more than 20 mg/l. Clostridium sp. SS1 also effectively reduced toxic Cr(VI) into the comparatively less toxic trivalent form. The optimum pH value for Cr(VI) reduction was 7.0, and the cells reduced Cr (VI) more efficiently at 30°C than at 20 and 40°C. Within the same incubation time, higher amounts of Cr(VI) were reduced at higher initial Cr(VI) concentrations (range 5-40 mg/l). Clostridium sp. SS1 had a higher volumetric [0.82 mg Cr(VI)/l/h] and greater capacity [72 mg Cr(VI)/g biomass] to reduce Cr(VI) at higher initial Cr(VI) concentrations (40 mg/l), suggesting that this strain could be potentially useful for the detoxification of Cr(VI) polluted sites.

Hexavalent chromium is a toxic heavy metal in environment. To remove it from the system, reduction to the trivalent form using microorganisms is an alternative cost-effective method compared to the conventional physicochemical methods. Bacillus cereus Pf-1was isolated and tested for the reduction potential of Cr (VI) using different sub-cellular fractions. Diphenylcarbazide method was used to measure the remaining Cr (VI) concentration in supernatant after centrifugation, and the pellet was used for Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis. Almost complete reduction of Cr (VI) was reported for initial Cr (VI) concentration from 10-50 mg/L. Assay with permeabilized cells (treated with Toluene and Triton X-100) and cells free assay demonstrated that Cr (VI) reduction activity was mainly associated with the cytoplasmic fraction of the cells. Considering the major amount of Cr (VI) being reduced within 24 h, the chromate reductase could have been released during growth. Additionally, SEM analysis showed that Bacillus cereus treated with Cr (VI) grew well and had uniform size. EDX analysis revealed certain amounts of chromium in cells treated with Cr (VI). Based on this, Bacillus cereus Pf-1 could be considered as a potential reducing agent for Cr (VI) in aqueous solutions.

This chapter examines the situation of rural water and sanitation services in Cameroon within the context of sustainable development goals (SDGs), to establish whether Cameroon is on right track of meeting the SDG, and proposes actions to be taken to achieve universal access for water and sanitation. Based on the analyzed data obtained from national surveys and the Joint Monitoring Program for 2021, it argues that Cameroon is unlikely to reach universal access to water and sanitation in rural area by 2030. Factors contributing to poor access to rural water and sanitation services include the poor application of the policy and legal framework, the poor coordination of interventions between the actors involved in the sector, the low financial viability of the sector, the low efficiency of expenditure related to water and sanitation, and the lack of human resources in the sector. The implementation of the policy and legal framework, the stability of the institutional framework, the reaffirmation of the major role of the State of the changed Ministry of water, and the collaboration of all the actors of the sector within the mechanisms provided for this purpose are of fundamental importance to achieve SDG 6.1 and 6.2 in Cameroon.

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