The aim of the current study is to determine the impacts of leachate recirculation on the degradation of three compositions of municipal solid waste in anaerobic bioreactors. The study was completed by using six columns with equal volume (0.042m3) containing different densities and compositions of solid waste, in order to follow waste degradation over a limited time. Three compositions of waste were studied: simulated fresh waste of standard composition, simulated fresh waste of fermentable composition, and actual aged waste. Measurements of the significant parameters including pH, leachate conductivity, Chemical Oxygen Demand (COD), and waste settlement, were carried out. The quantity of oxidized organic matter was increased by the leachate recirculation, and the degradation period was reduced by using leachate recirculation. After 300, 150, and 480 days, waste stabilization seemed to be reached for fresh, aged, and fermentable waste, whereas the organic content decreased to 650, 480, and 4000mg COD/L, respectively.

Solid waste generation and composition in Baghdad is typically affected by population growth, urbanization, improved economic conditions, changes in lifestyles and social and cultural habits. A burning chamber was installed to burn cellulosic waste only. It was found that combustion reduced the original volume and weight of cellulosic waste by 97.4% and 85% respectively. A batch composting study was performed to evaluate the feasibility of co-composting organic food waste with the cellulosic bottom ash in three different weight ratios (w/w) [95/5, 75/25, 50/50]. The composters were kept in controlled aerobic conditions for 7 days. Temperature, moisture, and pH were measured hourly as process successful indicators. Maximum temperature ranged between (41 to 53) ºC. Results showed that the blend of M2 [OFMSW: BCA] [75:25] was the most beneficial to composting. It maintained the highest temperature for the longest duration for 9hrs. at (53) ºC, achieved the highest nitrogen content(1.65%) , a C/N ratio of (14.18 %), nitrification index(N-NH4/N-NO3) of (0.29),nitrogen, phosphorous and potassium(NPK)(1.65, 1.22, 1.73)% respectively, seed germination 80% indicating that the achieved compost is mature and stable.        Heavy metal contents (Cd, Cr, Cu, Mn, Ni, Pb and Zn) were detected in the above compost and all were lower than the regulation limits of the metal quality standards for compost and stabilized bio-waste.