Effect of some operational parameters on the decolorization of textile effluents and dye solutions by ozonation.

Treatment of three wastewaters and two acid dye solutions by ozonation with varying ozone dose, initial pH, and initial dye concentration were examined. Ozonation of all the wastewaters were shown to be pseudo-first-order reaction with respect to color, chemical oxygen demand (COD) and dissolved organic carbon (DOC). Increasing ozone dose increased the removal of color, COD, and DOC, as well as decreased ozone consumption ratio, and increased apparent rate constants. Ozonation was more successful at decolorization than the removal of COD and DOC or augmentation of biodegradability. Increasing initial dye concentration increased the ozone consumption and decreased the rate constant. Color removal efficiencies for different ozone dose application were in the range of 60-91% for sample A (dye bath effluent), and 70-96% for sample B (plant effluent). For sample A, COD and DOC removal efficiencies at several ozone dose applications were between 13-22 % and 8-13%, respectively. For sample B, they were between 11-33% and 6-15% respectively. Increasing pH could expand the efficiency of ozone slightly. Ozone consumption per unit color, COD and DOC removal at any time was found to bealmost the same whereas the applied ozone dose was different at a constant pH. Ozonation increased the biochemical oxygen demand (BOD,) of sample A and B 1.22 and 1.37 times by consuming 300 and 225 mg ozone, respectively. Ozonation of acid dyes was a pseudo-first order reaction with respect to dye. Increases in dye concentration raised specific ozone consumption. Specific ozone consumption for Acid Red 183 (AR-183) dye solution with 50 mg l(-1) of concentration rose from 0.32 to 0.72 mg-O3 per mg dye decomposed as the dye concentration was increased to 500 mg l(-1).

Planning of wastewater treatment and disposal systems of Istanbul metropolitan area.

Current and future wastewater treatment and disposal strategies of Istanbul city are presented. Istanbul is the largest city of Turkey and has a population of 10 million that may reach about 20 million in 2032. The city is divided into Asian and European sides by the Bosphorus Strait. The Sea of Marmara is an enclosed sea, connected to the Black Sea and Aegean Sea by the straits of Bosphorus and Dardanelles. Therefore, there is very strong and permanent stratification in the Sea of Marmara throughout the year, lower layers carrying Mediterranean and the upper layers carrying Black Sea water. This unique coastal structure of Istanbul necessitated a detailed study to determine the level of wastewater treatment and the location and depth of marine outfalls. A comprehensive three-dimensional water quality modelling study concluded that tertiary treatment including nitrogen and phosphorus removal is required for the effluent discharges into the Marmara Sea. However, enhanced primary or even primary treatment has been found satisfactory for discharges into the lower layers of the Bosphorus and into the Black Sea. Provisions for upgrading to secondary treatment were recommended. The status of existing and planned wastewater treatment plants and sea outfalls of Istanbul city are also presented. Although the amount of treated wastewater was only 63 percent in 1998, a target of 95 percent treatment level by the end of 2000 has been adopted in implementation plans. All treatment plants are located at or close to the coast except Pasakoy WWTP which is in the catchment area of Omerli Reservoir, the major source of drinking water for Istanbul city. The Pasakoy WWTP has been designed to treat wastewaters collected from the catchment area of Omerli Reservoir to tertiary level before ultimate disposal. The implementation programme together with the cost estimates are given. Total investment on water, wastewater and stormwater projects up to year 2032 is estimated at about 10 billion US Dollars. The share of the wastewater projects in this total is increasing with time. The financial analysis concluded that investments for a Higher Demand Scenario can be realised by raising the water tariffs to 1.0 $/m3 for Phase 1 and 0.9 $/m3 for Phase 2.

Joint operation of small wastewater treatment plants in southern Turkey.

In this study, joint operation of several small wastewater treatment plants (SWWTPs) by the same operation company is proposed to avoid operational problems such as unqualified personnel, inadequate maintenance and laboratory services. Some case studies from Antalya province of Turkey are presented. Several SWWTPs are operated by the companies formed with the proportional shares of the owners such as ALTAS and TURAS. The performance data of the five treatment plants operated by ALTAS and two treatment plants operated by TURAS are presented. The status of wastewater treatment with emphasis on the small sized plants is also presented and evaluated. The percentage of small settlements served with sewer and wastewater treatment facilities is very low (3%) indicating that high volumes of investment are needed to increase the level of service to those of the developed countries. At present, the total number of the treatment plants in Antalya region is 409 with capacities ranging from 73 to 175 m3 d(-1). Package activated sludge type SWWPs built especially in the coastal regions meet the local effluent standards.

Centralised versus decentralised treatment and disposal options for Küçükçekmece Basin of Istanbul city.

Küçükçekmece Lake is a sea lagoon located on the European side of Istanbul city with a drainage area of 4 million inhabitants (year 2040). The original plan to treat all of the wastewater collected from the drainage basin in a single plant located at the Northern end of the lake is compared with the decentralised option involving 4 treatment plants. The initial investment cost of the decentralised option is estimated to be higher than the original plan by an amount of 43 million US $. However, the decentralised option has been chosen finally, considering the low cost and risk of wastewater collection, the possibility of the staging of the services, and the reduced environmental impacts.

Effect of ozone injection location on filter performance in direct filtration.

Two identical pilot scale sand filters were operated in parallel to study the effects of preozonation in direct filtration. No coagulants were used. The influent of one filter was ozonated, whereas the influent to the second filter was aerated. Significantly improved reduction in turbidity, particle count, and iron was observed with the filter receiving preozonated water. The head loss development rate was increased as a result of using ozone. In a second set of experiments, the effects of ozone injection point on filter performance were investigated. Two identical filters both receiving preozonated water were operated. With one of the filters, the raw water was ozonated immediately before it entered the filter. The entrance of the preozonated water to the other filter was delayed by using a detention tank between the ozone contact chamber and the filter. In addition to effluent turbidity and particle count values, zeta potentials of the waters entering the two filters were measured. Head loss development at several locations within each filter bed was also observed and recorded. Slightly better effluent quality (turbidity and particle count) was observed with the filter receiving preozonated water without delay. It was observed that the zeta potential of the prezonated water became more negative with increasing delay time.

Advanced treatment of high strength opium alkaloid industry effluents.

The purpose of this study was to investigate an effective treatment system which can be applicable to treat opium alkaloid industry (OAI) effluents characterised with high COD, TKN, dark color and non-biodegradable organic pollutants. In the first phase of the study, lab-scale anaerobic (UASBR) + aerobic (SBR) treatability studies were carried out on opium processing industry effluents. Effluent CODs from the two staged biological treatment system were relatively high (-700 mg l(-1)) and additional post treatment was required. Physico-chemical treatability studies previously carried out on the effluent of opium alkaloid wastewater treatment plant, were not effective in removing residual COD and color. In the second phase of the study, the refractory organics causing higher inert COD values in the SBR effluent were additionally treated by using Fenton's Oxidation. The batch tests were performed to determine the optimum operating conditions including pH, H2O2 dosage, molar ratio of Fe2+/H2O2 and reaction time. It was found that removal efficiencies of COD and color for 30 minutes reaction time were about 90% and 95%, respectively. The ratio of H2O2/FeSO4 was determined as 200 mg l(-1)/600 mg l(-1) for the optimum oxidation and coagulation process at pH 4. Experimental results of the present study have clearly indicated that the Fenton's oxidation technology is capable to treat almost all parts of the organics which consist of both soluble initial and microbial inert fractions of COD for opium alkaloid industry effluents. Effluents from the Fenton's Oxidation process can satisfy effluent standards for COD and color in general.

An innovative photocatalytic technology in the treatment of river water containing humic substances.

This study addresses the application of a photoelectrocatalytic (PEC) system with separated hole and electron reactions to treat humic acid (HA) from river water. A TiO2 electrode, coated by the sol-gel method, is used for that purpose. The degradation of humic acid in the river water was followed with respect to time using parameters of UV254, color and total organic carbon (TOC). For comparison purposes the photocatalytic (PC) removal of HA was also studied on the same photoanode. The obtained results showed that the PEC system was much more effective than the PC method. The effect of other important reaction variables, such as external potential, oxygen and UV intensity on HA degradation were also investigated. For all the external applied potential conditions and UV intensity range over 90% removal of UV254 and color were obtained with the PEC system while TOC removal was between 58-80%.