The Effects of Treated and Untreated Oil Mill Wastewater on C and N-Dynamics of a Sandy Loam Soil

Olive mill wastewater (OMW) is characterized by high pollutant load and phytotoxic levels of polyphenols, but also a high amount of organic compounds and plant mineral nutrients. For this reason, there is a potential to be used as a material improving soil after treated. In this study, OMW treated with two different treatment processes (economic pre-treatment and advanced treatment process) and untreated OMW were applied to a sandy loam texture soil at the rates of 0, 50, 100, 150 m3 ha-1 and the changes in C-and N-dynamics of soil and some chemical properties were determined. The experiment was carried out in total period of 90 days of incubation under laboratory conditions. Amendment with untreated and treated wastewaters increased the contents of total organic C (TOC), total N (TON), soluble- C (SOL-C), microbial biomass-C and N (MB-C and MB-N) and available P and K, but inorganic-N (INOR-N) pool decreased due to N-immobilization. The highest the ratios of MB-C/TOC, SOL-C/TOC and MB-N/TON were determined at the low OMW rates and the highest INOR-N/TON at the control and highest untreated OMW rate. These results showed that microbial biomass increased at 50 and 100 m3 ha-1 OMW rates but C-and N-dynamics of soil negatively were affected by 150 m3 ha-1 OMW applications. The fact that OMW that are minimized phenol and organic C load are applied to soils at not exceeding 100 m3 ha-1 rate may be considered to be a good strategy for recycling this waste