Turgay Pekdemir

Optimum Conditions for Washing of Crude Oil-Contaminated Soil with Biosurfactant Solutions

This paper presents the optimum conditions for washing Ekofisk crude oil-contaminated soil with biosurfactant solutions using the Taguchi experimental design method. The optimum values obtained through experimental runs were used to predict crude oil removed at three confident intervals (90, 95 and 99%). Results obtained through experimental runs and predicted crude oil removal were compared and used to access the robustness of the washing method. The biosurfactants tested were aescin, lecithin, rhamnolipid, saponin, tannin and a synthetic surfactant, sodium dodecyl sulphate. The experimental parameters and their four value levels investigated were: temperature (5, 20, 35 and 50° C); concentration of surfactant solutions (0.004, 0.02, 0.1 and 0.5%-mass); volume of surfactant solutions (5, 10, 15 and 20 ml); shaking speed (80, 120, 160 and 200 strokes/min) and washing time (5, 10, 15 and 20 min). Results showed that the optimum washing conditions for temperature and time were found to be 50 C and 10 min for all the surfactant solutions. The other parameters show optimum values at different point. However, SDS, rhamnolipid and saponin show an oil removal of greater than 79%. The washing method was found to be more stable at error of ± 1% for all the surfactant solutions except aescin and lecithin. Therefore, we suggest the applicability of this method in decontaminating crude oil-contaminated soil at the field scale.

Drinking water denitrification by a membrane bio-reactor

Drinking water denitrification performance of a bench scale membrane bio-reactor (MBR) was investigated as function of hydraulic and biological parameters. The reactor was a stirred tank and operated both in batch and continuous mode. The mixed denitrifying culture used in the batch mode tests was derived from the mixed liquor of a wastewater treatment plant in Erzincan province in Turkey. But the culture used in the continuous mode tests was that obtained from the batch mode tests at the end of the denitrification process. The nitrate contaminated water treated was separated from the mixed liquor suspended solids (MLSS) containing active mixed denitrifying culture and other organic substances by a membrane of 0.2 microm average pore diameter. The results indicated that the use of a membrane module eliminated the need for additional post treatment processes for the removal of MLSS from the product water. Concentration of nitrite and that of MLSS in the membrane effluent was below the detectable limits. Optimum carbon to nitrogen (C/N) ratio was found to be 2.2 in batch mode tests. Depending on the process conditions, it was possible to obtain denitrification capacities based on the reactor effluent and membrane effluent up to 0.18kgm(-3)day(-1) and 2.44 kg m(-2) day2(-1) NO(3-)-N, respectively. The variation of the removal capacity with reactor dilution rate and membrane permeate flux was the same for two different degrees of [MLSS]0/[NO3-N]0 (mass) ratios of 25.15 and 49.33. The present MBR was able to produce a drinking water with NO(3-)-N concentration of less than 4 ppm from a water with NO3-N contamination level of 367 ppm equivalent to a NO(3-)-N load of 0.310 kgm(-3) day(-1). The results showed that MBR system used was able to offer NO(3-)-N removals of up to 98.5%. It was found that the membrane limiting permeate flux increased with increasing MLSS concentration.