Exposure to sewage sludge may cause different infectious diseases to human health, but the main reasons are direct contact of sewage sludge in agricultural lands by the farmers and consumption of fruits, grains, vegetables, etc., that are grown in sewage applied agricultural lands. Uses of the sludge in agricultural purposes after treatment may increase the soil fertility and act as alternatives sources in compare with chemical fertilizers. The result showed that the cultivated using the treated sludge in ratio with the soil, was safe and didn't act any hazardous to the human consumption. The study concluded that the quantity of sludge production depends on the type of wastewater treatment and the plant capacity, and the rate of biogas production depends on the ratio of sludge and agricultural solid waste and the mixing temperature of the digester. Due to the prominent levels of the element of Fe and Cd in the sludge, which may appear in the risk evaluation. The study showed that the uses of sludge produced from the wastewater treatment plant in biogas production may be environmentally safe and economical. The Risk Assessment Code (RAC) considers the percentage of heavy metals present in the mobile fraction (F1). The RAC was also used to assess the environmental risks posed by heavy metals. The RAC was used to assess soil contamination with heavy metals from sewage sludge and sewage sludge ashes. The observation showed that there were no associated risks with the soil mixed samples used in the study.