Ayhan Ünlü

Role of intermittent aeration in domestic wastewater treatment by submerged membrane activated sludge system

Abstract In this study, the treatment of domestic wastewater in a lab-scale submerged membrane activated sludge system (sMBR) was investigated under different aeration intervals. The COD concentration of the system effluent varied generally between 5 and 25 mg/l and the COD removal at the organic loads of 0.6–0.8 kg COD/m3.d was observed to be above 98%. The total phosphorus content of the filtrate was decreased to a level that was less than 1 mg/l under the aerobic conditions in which the aeration was continuously made. A dramatic increase in the total phosphorus content of filtrate was observed under the aerobic + anoxic conditions in which the aeration was made at differential intervals. The filtrate was free of suspended solid (SS) and total coliform bacteria and a percent removal of 100 was achieved in terms of these parameters. The influent turbidity removal was 97–99.8%. Generally, the removal of total Kjeldahl nitrogen (TKN) and ammonium nitrogen varied in the ranges of 87.8–99.1% and in the ranges of 89.4–99.8%, respectively. While the nitrate concentrations in the filtrate increased to 26.8 mg/l under the aerobic conditions, it was determined that this value was decreased to 2.4 mg/l under the aerobic + anoxic conditions.

Viability of microbial mass in a submerged membrane bioreactor

In this study the viability of biomass in a submerged membrane activated sludge system (sMBR) which treats domestic wastewater was investigated by dealing with non-biodegradable COD, specific oxygen uptake rate and MLVSS during operation for 100 days. It was shown that the viability of biomass in the bioreactor was reduced at the 50% level because of the accumulation of inert compounds and the reduction in the activities of poor biomass. After inoculating the bioreactor again, the specific OUR increased because of young biomass entering into the bioreactor. It was shown that there was an exponential relationship between OUR and MLVSS and there was a logarithmic relationship between specific OUR and MLVSS.

Production of non-biodegradable compounds based on biomass activity in a submerged ultrafiltration hollow fibre membrane bioreactor treating raw whey

Raw whey including a high organic load in the range of 16–60 kg/m 3 per day was treated directly in a submerged membrane bioreactor (sMBR). The behavior of non-biodegradable compounds in the system and their effects on biomass viability were investigated by considering different sludge ages in the range of 10–75 days during an operation of 114 days. Non-biodegradable compounds were produced by dead and old organisms and then accumulated in the system. Furthermore, biomass viability decreased with an increase in sludge age. At sludge ages of 10 and 20 days, inert COD, which is a measure of non-biodegradable compounds, was removed together with the wasted sludge as a small amount of the system, but not taken away from the bioreactor at higher sludge ages due to the small amount of the wasted sludge. The production of non-biodegradable compounds was very clear at high sludge ages in the range of 30–75 days. Inert COD increased to 1.84 times at the fifth period when the sludge age was 75 days, based on the reduction of biomass viability. The ratio of mixed liquor volatile suspended solid to mixed liquor suspended solid (MLVSS/MLSS) decreased with time although both concentrations increased. The relationship between specific oxygen uptake rate (sOUR) and MLVSS was a logarithmic decreasing curve. The relationship between the sOUR and the Cs/C0 means that the ratio of inert COD concentration in the effluent to that in the influent was an exponent decreasing curve.

Optimal design of sedimentation tanks for effluent of marble works and use of settled solids in concrete

The aims of this study are to determine the settling characteristics of wastewater from the marble works in Elazig-City province experimentally and to optimise the dimensions of the sedimentation basins. The results can be directly used in small plants. Quiescent settling experiments were carried out at constant temperature for retention times of 0.5 to 2 hours by taking composite samples of two hours. The results obtained from through frequency distribution curves have shown that the settling was of a discrete type. The relationship between the hydraulic loading and the efficiency curves was obtained and thus the efficiency value of basins at different surface areas was determined. The dimensions of the basins for minimum turbulence, stable flow without bottom drift and maximum settling efficiency were investigated. The Froud Number that expresses the flow stability, the Reynolds Number that indicates the turbulence effect, and the horizontal velocities at basins were considered as limiting factors, while the surface areas of basins were held constant. The basin 9, with surface area of 80 v m 2 (4 v m 2 20 v m), is the most suitable one with efficiency of 99.5%. Basin 7, with surface area of 45 v m 2 (3 v m 2 15 v m), where the efficiency could be increased by building an entry region, is the most economic one according to construction. The use of settled solids at the bottom of basin within concrete classes C14 and C20 was experimentally investigated through compression tests. The compression strength of cube samples adulterated with the settled solids for both concrete classes of C14 and C20 were 3-4% better than the cube samples with normal aggregate.