The results of ICP‐OES analysis with (EPA 200.7) method serve as a proof of the negative influence of inorganic (As) from the processing of drinking water on the quality of anaerobic digested sludge. Detection of these proportions has for the first time confirmed the migratory flow of arsenic from the source point technological wastewater at Water intake 1 through the city sewage network to the wastewater treatment plant (WWTP) in Subotica. Arsenic (As) with low concentration at the input of the WWTP has ranged from 0.029 to 0.05 mg/L, but after anaerobic digestion, arsenic concentration in the sludge still showed a limiting character, which has caused a decrease in its quality and the possibility of wider utilisation. In order to preserve the quality of the potential biological product at WWTP, the impact of migratory arsenic must be prevented, and inertness of waste has to be achieved by the introduction of stabilisation/solidification technologies.

Anaerobically stabilized sludge from wastewater treatment is always a challenge from the environmental aspect of management. The agrarian environmental surroundings present a possibility for swift and efficient utilization of compost from anaerobically stabilized sludge in order to increase the quality of the biological product. With intensification of the composting procedure by means of the microbiological consortium Geocell‐1 (Cellvibrio sp., Pseudomonas fluorescens with the addition of micro‐ and macro‐elements), the results show that the compost obtained from stabilized sludge after inoculation is significantly improved in terms of moisture reduction (39–43%), while in the control compost, this value is significantly higher with 61%. The results of the pathogenic effect show a significant reduction in the number of fecal coliform (<1 × 103) and Enterococcus bacteria (<1 × 104) in the inoculated (treated) compost. With a slight decrease in the concentration of limiting factors such as As, Cd, Cu, a quality biological product can be achieved, which can be safely deposited on soil. The phytotoxicological germination test with white mustard (Sinapis alba) shows a higher number of sprouting plants with a mixture of treated compost and standard soil for flowers 1:1 and 1:4 compared to the control group.