Little Akaki River (LAR) is one of the major rivers passing through the Addis Ababa City Administration and is often receiving untreated wastes from residential, industrial, municipal, and agricultural areas. The objective of the study was to determine pollution profile of LAR, develop and evaluate the performance of a pilot HSSFCW system for LAR water; and to assess the suitability of treated river water and sludge for agriculture. LAR water and sediment were first evaluated using various pollution indices and multivariate statistical analyses. The water samples collected from the river, outlet of sedimentation tank, and outlet of HSSF-CW for analysis of phsico-chemical parameters following standard methods. While heavy metals concentration in water, wetland plants, and vegetable samples were determined using inductive coupled plasma optical emission spectrophotometry (ICP-OES). The heavy metals bioavailability and mobility in sludge was determined using sequential extraction procedures proposed by the European Bureau of References (BCR). The comprehensive water pollution index values of LAR ranged: 0.84 -13.32, indicating that LAR was heavily polluted (CPI > 2.01). Principal component analysis explaining 88.99% variance in the data set indicated that organic pollutants, dissolved salts, nutrients, and trace metals are the main sources of factors influencing river water quality. The enrichment factor analysis results showed that the LAR sediments were moderate to very highly enriched with Pb and Cd. The ecological risk index (RI =350.62) suggested that the contaminated sediment can pose considerable ecological risks to aquatic biota. The overall treatment efficiency of the pilot HSSF-CW planted with Typha latifolia, which is tolerant, adaptable to study area, and effective in removal of heavy metals and other pollutants, the organic pollutants and suspended solid removal rate were 81.75% for BOD; 75.07% for COD, and 96.08% for TSS. The nutrient removal rate was 86.82% for NO3-N, 82.09% for SO4-2 and 87.13% for PO4-3, while the heavy metals removal efficiency was 50.2% for Zn; 91.18% for Cr; 77% for Cd, and 72.07% for Pb, indicating varied removal rate may be due to preferential sequestration, adsorption and varied metals solubility. Moreover, the quality of HSSF-CW treated river water meets the international irrigation water quality guideline limits set in FAO and USEPA, except for Cd which is slightly exceeded the guideline limit. Heavy metals bioavailability analysis result showed: 39.17% of Zn; 19.22% of Cr; 30.23% of Cd, and 31.25% of Pb were in bioavailable form. Whereas, the average mobility factor (MF) of all traces metals was 67%. The risk assessment code revealed that all trace metals fall in the medium to high environmental risk classes. Thus, due to mobility, bioavailability, and environmental risks of toxic metals, reuse of sludge as organic fertilizer on agricultural cropland may adversely affect the environment and public health. However, the sludge can be used as organic fertilizer for growing trees and ornamental plants in contained areas and in parks. Thus, it can be concluded that HSSF-CW treatment system is a viable technology to improve the quality of polluted river water.