Performance of wastewater treatment plants in Gaza Strip potential use of wastewater and sludge in agriculture

Twelve elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were analyzed in 120 composite samples of influent and effluent wastewater; the results revealed that domestic wastewater influent contains considerable amounts of heavy metals and the partially functional treatment plants of Gaza are able to remove 40-70% of most metals during the treatment process. Heavy metals in 31 industrial wastewater effluents are within the ranges of international standards. AN industries of Gaza are light, despite that they have no treatment facilities, their effluents are being discharged to municipal sewerage system and the existing treatment plants are capable to absorb the industrial effluents with no significant impact on treatment bioprocesses. Thirty parameters were determined in 35 sludge samples; P, AOX, C, S, CaCO3, Mg, Ca, Na, K, Li, Cu, Zn, Ni, Pb, Mn, Fe, Cr, Co, Cd, As, Hg, Ti, Se, Br, Rb, Th, Sr, Y, U, and Zr. Although there are no treatment facilities for sludge within the treatment plants, the results indicated that sludge in general is clean of heavy metals. Zinc and AOX only showed anomalous concentrations; more than 85% of sludge samples showed that averages of zinc and AOX are 2000 mg/kg and 550 mg Cl/kg, respectively, which exceed the standards of all industrial countries for sludge to be used in land application.