The Palestinian water strategies entail erection of new and upgrading of old wastewater treatment plants (WWTPs) to cope with increase sludge production, which is currently landfilled. Achieving a sustainable sludge management including resource recovery through sludge land application in Palestine warrants the study of the degree of sludge stabilization.
The aim of this study is to identify and analyze the sewage sludge produced from different WWTPs in view of its suitability for agricultural use in Palestine. The research focuses mainly on pathogenic and agronomic values of wastewater sludge; considering the nutrient elements and potential impacts on the soil environment. To assess pathogens and agronomic value of different types of sludge, a quantitative research methodology was adopted. Two types of sewage sludge fresh and treated sludge was analyzed and compared with characteristics of stable sludge permitted for agricultural application. In addition to selective pathogens (TC) and (FC), the agronomic parameters selected were percentage of volatile suspended solids (VSS%), totals suspended solids (TSS), total nitrogen (TN) content, total phosphorus (TP) chemical oxygen demand (COD), pH and electrical conductivity (EC). Sludge samples from different treatment processes (aerobic, anaerobic, dewatered and dried) were collected from four different WWTPs and results were assessed for compliance to limits of local and international sludge quality standards. The results will deliver scientific evidence on satisfying the needs in fertilizers and the fulfillment of both quantitative and qualitative needs of the plant, while ensuring environmental safety. This study is significant in contributing to the understanding of health and environmental impacts of using stabilized sludge for soil amendment or as fertilizer.
Findings clarify that sewage sludge (biosolids) pathogenic characteristics comply with Palestinian sludge guidelines, where the FC results were below log 6. Moreover, the sludge stability in terms of VSS% recorded values in range between 68% - 80% near to stabilized sludge criteria. On other hand, the nitrogen and phosphorus content recorded rich amounts of these nutrients in all types of sludge samples plus the N/P ratio was recorded an average of 4 which is typically describe the stabilized sludge. Moreover, the results for pH and EC comply with commercial compost characteristics. This allow stakeholders to consider biosolids land application as a good option for sludge management furthermore; this will be helpful for decision makers and farmers in view of bioresource recovery as a cost-effective recycling of sludge produced.