Sustainable Hospital Laboratory Wastewater Management: Characterization, Segregation, and Controlled Blending for Safe Discharge into Municipality

Hospital laboratory wastewater (HLW) presents severe environmental, occupational, and infrastructure risks due to its complex, highly variable, and hazardous composition. In facilities lacking dedicated on-site treatment plants, unmanaged discharge into public sewers threatens municipal biological treatment systems and receiving aquatic ecosystems. This study presents a comprehensive characterization and source-segregation management framework for HLW generated across five diagnostic units—hematology, immunology/serology, histopathology, parasitology, and clinical chemistry—at a major hospital in Cairo, Egypt to assess compliance with national regulatory limits for municipal sewer discharge. Investigated streams demonstrated extreme heterogeneity: routine hematology and urine parasitology met municipal discharge standards, whereas clinical chemistry and serology exhibited elevated COD (up to 5511 mg/L), phenol (up to 1.2 mg/L), and boron (up to 36.7 mg/L). Histopathology waste was highly polluted (COD > 45,000 mg/L, BOD5 > 8800 mg/L, oil and grease 4472 mg/L) while specific blood-laden hematology streams recorded COD values up to 18,639 mg/L. Rather than applying unselective dilution, a quantitative four-tiered framework was implemented. Source segregation combined with controlled equalized blending and batch chlorination enabled 56% of the total laboratory wastewater volume to safely comply with municipal sewer standards leaving 44% of hyper-hazardous volume for specialized off-site contractor disposal. Compared to full off-site contractor hauling or installing capital-intensive treatment infrastructure, this strategy reduces disposal costs of 56% of wastewater without requiring capital investment, providing a practical, scalable model for healthcare facilities. This eco-efficient management strategy reduces off-site disposal costs by 56% without requiring capital expenditure (CapEx), providing a practical, scalable decision tool for healthcare facilities to advance sustainable development goals (SDG 6 and SDG 12) in resource-constrained settings.