Improving the sludge disintegration efficiency of sonication by combining with alkalization and thermal pre-treatment methods.

One of the most serious problems encountered in biological wastewater treatment processes is the production of waste activated sludge (WAS). Sonication, which is an energy-intensive process, is the most powerful sludge pre-treatment method. Due to lack of information about the combined pre-treatment methods of sonication, the combined pre-treatment methods were investigated and it was aimed to improve the disintegration efficiency of sonication by combining sonication with alkalization and thermal pre-treatment methods in this study. The process performances were evaluated based on the quantities of increases in soluble chemical oxygen demand (COD), protein and carbohydrate. The releases of soluble COD, carbohydrate and protein by the combined methods were higher than those by sonication, alkalization and thermal pre-treatment alone. Degrees of sludge disintegration in various options of sonication were in the following descending order: sono-alkalization > sono-thermal pre-treatment > sonication. Therefore, it was determined that combining sonication with alkalization significantly improved the sludge disintegration and decreased the required energy to reach the same yield by sonication. In addition, effects on sludge settleability and dewaterability and kinetic mathematical modelling of pre-treatment performances of these methods were investigated. It was proven that the proposed model accurately predicted the efficiencies of ultrasonic pre-treatment methods.

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).

Decolorization of textile wastewater by ozonation and Fenton's process.

The aim of this study is to investigate the effect of some operational parameters on the efficiency of ozonation and Fenton's process for decolorization and COD removal. Acid Red 337 and Reactive Orange 16 dye solutions and the effluents of acid and reactive dye-bath effluents were used in the experiments. The influence of ozone dose and pH for color and COD removal from the wastewater were studied. Increasing the ozone dose increased the rate constants, and color and COD removal efficiencies. Ozone consumption ratio per unit color and COD removal at any time was found to be almost the same while the applied ozone dose was different. pH did not significantly affect color and COD removal from the wastewater by ozonation. In spite of having high color removal efficiencies (60-91%), limited COD removal efficiencies between 9-17% at 30 minutes ozonation time were obtained. In the Fenton oxidation experiments, the effects of pH, temperature, dosage of ferrous sulfate and hydrogen peroxide, and the proper ratio of Fe(II)/H2O2 were studied. The result indicates that up to 99% color removal and 82% COD removal can be obtained by Fenton's oxidation. While Fenton's oxidation was greatly affected by the pH value, temperature of wastewater did not significantly affect the Fenton process for color removal. Increasing the dose of both hydrogen peroxide and ferrous sulfate enhanced the removal efficiencies of color and COD. Suitable ratios of Fe(II)/H2O2 were found to be between 0.5 and 0.83.

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.

Application of membrane and ozonation technologies to remove color from agro-industry effluents.

The results of membrane and ozonation experiments carried out on various agro-industry effluents including fermentation (baker's yeast), corrugated board, opium alkaloid and textile dying industries are presented. The experiments were performed using lab-scale membrane and ozonation reactors. Color removals were in the range of 80 to 99% for the membrane treatment studies. Ozonation experiments have shown that color removals in the range of 83 to 98% are possible for the investigated wastewaters. Final color levels were lower than 100 Pt-Co unit, which is quite acceptable aesthetically. The relative unit treatment costs of ozonation were about two times higher than membrane systems especially for very strong colored effluents including fermentation and opium alkaloid industries. The study has demonstrated that both membrane and ozonation technologies are viable options for color removal.

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.

Quality of the bottom sediment prior to dredging in the Golden Horn of Istanbul.

The Golden Horn has experienced severe pollution due to uncontrolled domestic and industrial wastewater discharges until recent years. A restoration project has been developed by our universities, upon a request from Istanbul Metropolitan Municipality. Two principal alternatives for the dredging and disposal of the bottom sediments were considered: disposing on the land and disposing in the sea. Both of these alternatives include several sub-alternatives. Characterization of the sediment quality is crucially important for selecting the best alternative considering the cost, environmental impact and public acceptance. However, only a few and rather old studies were present with which it was not possible to get a comprehensive information on the critical sediment characteristics. Therefore, the aim of this study was determination of spatial distribution of sediment characteristics. The project area, at which the sediment quality determined, covers the part of the Golden Horn remaining at the upstream of Valide Sultan Bridge. The number of sampling stations were thirteen and the sediment samples were collected from 0.0m, 5.0m and 10.0m from the bottom surface. The following parameters were measured on each sample: Total solids, organic matter, total phosphorus, TKN, oil and grease, total sulphur, and sediment oxygen demand (SOD). Sediment oxygen demand parameter was further divided into three fractions, namely, biological (SOD-B) and chemical (SOD-C). Average organic content of the bottom sediment was around 10% while ammonia and sulfur exhibit very high levels. It is found that the bottom sediment is well stabilized with very low organic content below 5.0m from the bottom surface. It can be said that, removing the upper 5m of the bottom sediment will be enough for creating a relatively stable bottom surface which will cause oxygen depletion in the overlaying water at acceptable levels. High SOD values of the bottom sediment makes the alternatives considering disposal in the Marmara Sea and Black Sea inapplicable. High SOD-C values, especially, indicate that the sediment will cause a tremendous reduction in the oxygen concentration in a very short time at any marine environment, and even it may create anaerobic conditions. Therefore, disposal of dredged sediment into abandoned mines 4km from the Golden Horn by a pressure pipeline has been chosen as the best applicable alternative.