Heavy Metals Analysis of Breweries Effluent used in Soil Cultivated with Glycine Max (L.) Merr. Accessions with Biochar Augmentation

Beer production has promulgated the prevalence of heavy metal contamination in the environment (soil and water bodies). The magnitude of breweries wastewater-effluent effect discharged on soil and its effect on crop quality in terms of growth and physiology must therefore be investigated. This study aims to assess the level of seven heavy metals (HM) (lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), cadmium (Cd), zinc (Zn) and iron (Fe)) in breweries wastewater-effluent and its effect on the growth of Glycine max accessions (TGM-3990, TGM-1348, TGM-1732, TGM-2175 and TGM-928) as well as the influence of biochar soil amendment in the induction of HM tolerance in G. max. Effluent properties were analyzed using the A1 portable TDS/EC meter. HM in the wastewater-effluent was determined using Atomic Absorption Spectrometer (AAS). The experiment was set up in a complete block design. 3 seeds G. max accessions were planted in 7kg of sterilized soil (control, effluent and biochar treatments). Growth parameters were taken using standard methods, while the total photosynthetic pigments (TPP) were determined using the atLeaf chlorophyll meter. The wastewater-effluent recorded an electrical conductivity (EC) of 928µS/cm, total dissolved solids (TDS) (464ppm), Temperature (31.9-32.6°C) and pH (5.37). Results for HM concentration showed; Pb (0.20mg/L), Ni (<0.001mg/L), Cr (0.03mg/L), Cu (<0.001mg/L), Cd (<0.001mg/L), Zn (<0.001mg/L) and Fe (8.74mg/L). The trend shows that Fe˃Pb˃Cr˃Cd˃Cu˃Ni˃Zn. Cr, Cd, Cu, Ni and Zn were significantly below the World Health Organization (WHO) and Waste Water Forum (WWF) permissible limit, while Fe and Pb significantly higher. G. max accessions TGM-928 (80%) and TGM-3990 (80%) had better germination percentage (GP), TGM-1348 (60%) had the lowest GP, while TGM-2175 recorded no germination in all treatments. At 6 weeks after planting (WAP), it was observed that irrigation of G. max accessions with breweries wastewater-effluent significantly (p=0.001) stimulated growth parameters such as shoot length for TGM-3990 which recorded; Treatment=19.53±0.94cm; Control=17.10±0.67cm; Biochar=40.83±1.01cm) while TGM-1732 had the highest shoot growth (T=38.57±1.53cm; C=25.00±0.00cm; B=82.33±5.70cm) when compared to their controls. TGM-3990 (T=32.20mg/kg, C=34.10mg/kg, 43.30mg/kg) recorded the least TPP contents, while TGM-928 (T=51.00mg/kg, C=45.60mg/kg, B=43.50mg/kg) recorded the highest TPP in all treatments. Amelioration of soil with biochar significantly (p=0.001) stimulated growth above the effluent treatment and control. Similar trend was observed for leaf area, petiole length, leaf number, stem girth and internode length. This study has shown that breweries effluent has the potential of growth enhancement in G. max cultivation and in combination biochar application reduces the need for additional fertilizer application.