The Performance of Four Different Mineral Liners on the Transportation of Chlorinated Phenolic Compounds to Groundwater in Landfills

The aim of this study was to investigate the efficiency of four different mineral liners (clay, bentonite, kaoline, and zeolite) which could be utilized to prevent the transport of phenolic compounds to groundwater through alternative liner systems. Four laboratory-scale HDPE reactors with 80 cm height and 40 cm inner diameter were operated for a period of 180 days. Results indicated that the transport of mono- or dichlorophenols is significantly prevented by the liner systems used, while the transport of highly chlorinated phenolic compounds cannot be prevented by the landfill liner system effectively. Highly chlorinated phenolic compounds in groundwater can be found in higher concentrations than the leachate, as a result of the degradation and transformation of these compounds. Thus, the analysis of highly chlorinated phenolic compounds such as 2,4,6-TCP, 2,3,6-TCP, 3,4,5-TCP, and PCP is of great significance for the studies to be conducted on the contamination of groundwater around landfills

Characterisation of wastes collected from beaches, coastlines, marine surface cleaning processes and ships: A case study of Istanbul

Marine waste management is crucial for Istanbul because of the significant location for intercontinental transition, international trade, tourism, industry and shipping. This study is the first one realised in Turkey for the detailed characterisation of marine waste. The amount and characteristics of solid wastes originating from beaches, coastlines, sea surface cleaning processes and ships (both cargo and cruise ships) were determined. It was observed that marine wastes includes a significant amount of recyclable materials. Although, it was ascertained that the amount and composition of waste differs according to the collecting sources, the majority of wastes are composed of different types of plastics. The average calorific value of marine waste was determined as 2500 kcalkg-1, which is higher than that of mixed municipal solid waste. There is a lack of studies on the pathways of disposal alternatives of marine waste after collection. As landfilling is the common pathway for disposal after collecting, it is clear that recycle/reuse and energy recovery options are possible for marine waste

Evaluation of development in supercritical water oxidation technology

Supercritical water oxidation (SCWO) has been an innovative technology for the treatment of aqueous and hazardous organic wastes for 35 years. The technology provides cleaner output products and energy recovery. The purpose of this study is to evaluate the latest state of SCWO, which is an innovative and promising technology, according to the information obtained from the lab-scale, pilot-scale and full-scale applications. The process has been extensively used mostly in laboratory or pilot scale plants for model and real wastewater treatment. Industrial SCWO plants have usually closed due to corrosion, clogging and high cost problems. In order to operate this innovative technology efficiently, the main suitable wastewater should be selected, appropriate reactor design should be used, more durable materials should be produced, efficient pre-treatment should be determined so as to decrease operating costs and technical solutions should be determined. Otherwise, SCWO studies may be limited to laboratory and R&D studies

Supercritical water gasification of sewage sludge by continuous flow tubular reactor: A pilot scale study

Treatment and disposal of sewage sludge constitute one of the major problems of wastewater treatment plants due to high water content and more stringent environmental regulations. Supercritical water gasification (SCWG) technology is accepted as a promising method for sustainable sludge disposal because of the elimination of need for costly water reduction and drying processes before disposal by conventional methods. The aim of this study is to determine the effect of temperature (450–650 °C), solid matter content (1–2%) and catalyst addition (0.5–2% KOH) on supercritical gasification of sewage sludge in a continuous-flow pilot scale tubular reactor. The results indicate that the gasification efficiency is generally temperature dependent. Furthermore, catalyst addition improves the gasification efficiency at high solids content. The produced gas contains 60% of H2 and 22% of CH4 at experimentally determined optimal conditions (650 °C, 2% solid matter content, 2% KOH). The resulting gas contains H2S and CO below detection limits and there is no need for additional treatment. Consequently, SCWG technology provides complete decomposition of organic matter in a short time, clean gas formation with higher energy content, and volumetric reduction compared to conventional methods.Scientific Research Projects Coordinator-ship of Yildiz Technical University (BAP) Project Number: 2016-05-02-KAP01 and 2016-05-02-DOP0

Characteristics of liquid products in supercritical water gasification of municipal sewage sludge by continuous flow tubular reactor

Sewage sludge is a by-product of wastewater treatment, containing high water and organic content. Supercritical water gasification provides sustainable treatment for biomass sources such as sewage sludge. In this study, the effects of operating conditions (temperature, solid matter content and catalyst) and raw material properties on the resulting liquid products were determined in order to exhibit the success of this innovative technology for treatment and disposal of municipal sewage sludge using a continuous flow pilot-scale tubular reactor for the first time in Turkey. As a result of the study, it was determined that the higher the temperature, the higher the quality of the liquid product. TOC removal efficiencies increased from 84.4% to 99% with increasing the temperature from 450 to 650 °C, for 1% solid matter content. The pollutant concentrations in the liquid products increased by increasing the solid matter content of the raw sludge from 1 to 2%. This situation has been eliminated by the catalyst (KOH) addition, resulting in a very transparent liquid product. Additionally, TOC removal of 99.8% was obtained after addition of 2% catalyst. Thus, supercritical water gasification (SCWG) has been considered as a notable technology for the treatment and disposal of sewage sludge without the need of additional pre- or post-treatment

Prioritization of the treatment and disposal methods of wastes containing polychlorinated biphenyl by fuzzy multi-criteria decision-making and risk assessment

A total of 209 different types of polychlorinated biphenyls (PCBs) with various properties have been produced from 1930 to 1970s in which they have been banned due to their toxic effects. Total produced PCBs in the world are around 15 to 20 million tons, and up to now, 5.4 million tons of PCB-containing or PCB-contaminated equipment/materials has been eliminated. The remaining 10–15 million tons still needs to be removed or managed. Moreover, PCBs are pollutants still being unintentionally formed. These pollutants can be treated or disposed of various methods. However, there is a lack of knowledge about the selection of the treatment and disposal methods and their environmental, technological, cost, and social/ergonomic evaluation perspectives and the risk assessment during method selection. In this study, a projection was presented for the management of PCBs with an integrated multi-criteria decision-making (MCDM)-risk analysis focusing on these questions. Treatment (physical, chemical, biological) and disposal (incineration, landfill, supercritical water oxidation/gasification (SCWO/G), and pyrolysis/gasification) methods for the management of PCB-containing waste have been prioritized by fuzzy-analytical hierarchy process (F-AHP) in terms of environmental, technology, cost, and social/ergonomic criteria. Risk analysis was also made in terms of these criteria for considered alternatives, and compliance with risk and MCDM was evaluated. As a result of the study, priority methods among alternatives were determined as chemical treatment and SCWO/G. It has been determined that the weight values of the main criteria of environmental, technology, cost, and social/ergonomics were close to each other, but the emission criterion of the sub-criteria was determined to be of higher priority. In the risk analysis, chemical treatment and SCWO/G methods have been found to carry a more acceptable risk. Thus, it has been evaluated that these methods provide more superiority than other methods. © 2020, Springer Nature Switzerland AG

The risk analysis by failure mode and effect analysis (FMEA) and fuzzy-FMEA of supercritical water gasification system used in the sewage sludge treatment

Supercritical water gasification (SCWG) system is a hydrothermal conversion process used for the treatment of wastes with organic and toxic content and it is an especially promising technology for biomass with high water content such as sewage sludge. The interest in this technology is on a paramount increase because of both economic and environmental reasons. However, this system is marked by certain problems even though it has significant advantages. The aim of this study is to determine the problems that occur during the commissioning and operation of a continuously operated, laboratory-scale supercritical water gasification system and to identify their reasons and effects. For this purpose, cause-and-effect diagram, classical failure mode and effect analysis and fuzzy failure mode and effects analysis were carried out. As a result of the analyses performed, it has been concluded that the most important problems are plugging, corrosion, reactor design and incompatible material selection. As for the most important risks that occur in SCWG, they include explosion, injury, odor and noise. It has been seen that conducting a risk analysis of the SCWG system is important for job safety and sound operation. (C) 2017 Elsevier Ltd. All rights reserved

Comparison of methods for sustainable energy management with sewage sludge in Turkey based on SWOT-FAHP analysis

The sewage sludge creates as a result of wastewater treatment and has high water content, contains pathogens, heavy metals, micro-pollutants, etc., and also include organics that have a high calorific value, nitrogen and phosphor; therefore, it is necessary to select sustainable methods in its treatment/disposal. As for sustainable sludge management, not only current technologies, but also several other criteria such as legal regulations and problem-solving need to be taken into account. This study summarized the current situation for the management of domestic sewage sludge in Turkey and compared the methods of anaerobic digestion, incineration, gasification, pyrolysis and supercritical water gasification (SCWG), which are used/can be used in Turkey, with one another on the basis of four different criteria. As a result of the SWOT-FAHP (fuzzy analytic hierarchy process) analysis performed, it was observed that supercritical water gasification, which is one of the five methods considered, and problem-solving criterion, which is one of the four criteria considered, had the highest weight values. According to the results obtained via comparison of criteria, it was determined that the availability of current technology had less importance than problem-solving criterion in the selection of an appropriate method. The reasons why the method of supercritical water gasification had a high weight value even though it had certain disadvantages can be listed as follows: it ensures treatment with a high yield, does not require pre-treatment, has a shorter reaction time and creates a higher amount of beneficial by-products as compared with harmful emissions. Furthermore, this study also touched upon the obstacles to overcome for the development of SCWG and brought recommendations. (C) 2016 Elsevier Ltd. All rights reserved