Isolation and Identification of Bacteria from Groundwater Sources after Floods in Derna City, Libya.

Abstract

Flooding is the most common type of disaster globally, responsible for nearly half of all natural disaster victims and economic losses. During and after flooding, human exposure to microorganisms and chemical pollutants. This study aimed to assess and compare the quality of groundwater in Derna City, Libya, between affected and unaffected areas. The results were also compared with international drinking water guidelines recommended by the World Health Organization (WHO) and Libyan standards. A total of 50 groundwater samples were collected in September 2023 from both affected and unaffected regions in Derna city to assess their microbiological and some physical-chemical properties. The results of the water samples showed that pH values ranged from (6.97 to 7.82) in unaffected areas and from (6.99 to 7.96) in affected areas, indicating neutral to slightly alkaline conditions. Temperature in unaffected areas ranged from (19.5°C to 22.9°C) while in affected areas it ranged from (18.7°C to 22.5°C), These values were within the limits recommended by (WHO). Electrical Conductivity (EC) values in unaffected areas ranged from (1680 to 5210μS/cm), while in affected areas they ranged from (390 to 5214μS/cm), These results indicate that most samples exceeded permissible limits. Total Dissolved Solids (TDS) also exceeded permissible limits in most samples, with values ranging from (1070 to 3320mg/l) in unaffected areas, and from (260 to 3389.1 mg/l) in affected areas. All samples in unaffected areas were colorless, except for samples (S15, S17, and S19). Similarly, in affected areas, all samples were colorless except for (S25, S38, S39, S44, S48, and S49). Microbiological analyses showed the Total Bacterial Count in unaffected areas ranged from (50 to >300 CUF/ml), while in affected areas it ranged from (10 to >300 CUF/ mL). Total Coliform Counts ranged from (0 to >300 MPN/100mL) in unaffected areas, and from (0 to 240 MPN/100 mL) in affected areas. E.coli levels from (10 to >300 MPN/100ml) in the unaffected areas, while it was from (0-90 MPN/100ml) affected areas. SPSS analysis showed it was fond that most of the samples in the unaffected areas were seriously contaminated to Total Count it was in proportion (68.5%), Total Coliform Bacteria (84.6%) and E.coli (81.7%), as for the affected areas Total Count (31.5%), Total Coliform (15.4%), and Fecal Coliform (18.3%) except of some sample for the steam station was a natural result sample (S50), (S35), (S47), (S8), and (S5). The results revealed that bore well water is not safe for human consumption. The presence of indicator bacteria suggests potential contamination with pathogenic bacteria. Major contributing factors include the flood, aging water infrastructure, pipeline leaks, poor sanitation, and inadequate waste management.