Organic Load Input from the Sewage Outfalls along Tripoli Coast

Abstract

The study, which was conducted on seasonal samples (summer and winter), has concluded from sewage outfalls for five stations that located along the coast of the city of Tripoli, that wastewater contains high levels of all indicating pollution that showed (Massive Enrichments) with organic materials, and also showed (Eutrophication) with nutrients, where the measurements recorded very low dissolved oxygen with a concentration of 0.14 mg/L at the SPAN outfall in TAJOURA, and the highest value of the dissolved oxygen was at the outfall of SIDI ABDEL-JALIL with 4.18 mg/L for the same season (Summer), the values of the pH and the temperature of the wastewater came within the limitations of Libyan standard specifications, contrary to all other parameter targeted in the study, where the values of the pH ranged between 6.98 and 8.20 pH units, and temperatures between 19.20° and 22.10° in the winter, Between 27.80° and 28.6° in the summer, the results showed a difference in the BOD and COD values between the regions, where the lowest value of the biological oxygen demand is 51.00 mg/L in the summer at the outfall of HAI AL-ANDALUS station, and the highest value was 161.70 mg/L in the summer at the outfall of SPAN. As for the values of chemical oxygen demand, it ranged between 206.70 – 9221.70 mg/L at the overflow of HAI AL-ANDALUS station and SPAN for the summer and winter seasons, respectively. The results of the analysis of total suspended solid (TSS) were ranged between 39.00 - 252.30 mg/L. As for the nutrients, the total nitrogen concentration (TN) ranged between the highest and lowest values recorded at the outfall of ALSEYAHIA – AL-SARRAJ by 62.30 – 7833.30 mg/L for the summer and winter seasons, respectively, and the total phosphorus concentration (TP) Between the lowest value of 6.30 mg/L recorded in the summer, and the highest value of 31.70 mg/L recorded in the winter.  It has been found that he results of all pollutants determined were higher in wither season than in summer. On the other hand, the study estimated that more than 141,000 m³ of wastewater is discharged daily into the coastal area of the city of Tripoli.  The amount of organic load was found to be 10 tons /day for the summer season and 19 tons / day for winter. These values were equal to/or exceeding the guidelines values set by MAP of the Barcelona Convention. The guidelines value define that any point receives 10 tons of organic load in term of BOD per day is considered a HOT SPOT, which a polluted place that need a speedy state intervention. The obtained results also indicated that the wastewater discharged into the coastal area of the city of Tripoli was not subject to ant treatment even primary treatment processes.