Süleyman Yüce

Siloxane removal from landfill and digester gas – A technology overview

This paper reviews technologies for the removal of volatile methyl siloxanes (VMS) from biogas. More than 20 years after identifying silicon dioxide in gas engines running on landfill and sewage gas, three technologies are commercially available to remove siloxanes today: adsorption, absorption and deep chilling. Newer concepts based on technologies other than sorption or condensation have not yet gained access to commercial biogas purification. These emerging siloxane removal concepts include biotrickling filters, catalysts, membranes, and in the case of sewage gas, sludge stripping, peroxidation and filtration at point inlet source. This work introduces the main principles of commercial siloxane removal systems and reviews scientific progress in the field over the last decade.

Suitability of Tedlar gas sampling bags for siloxane quantification in landfill gas.

Landfill or digester gas can contain man-made volatile methylsiloxanes (VMS), usually in the range of a few milligrams per normal cubic metre (Nm(3)). Until now, no standard method for siloxane quantification exists and there is controversy with respect to which sampling procedure is most suitable. This paper presents an analytical and a sampling procedure for the quantification of common VMS in biogas via GC-MS and polyvinyl fluoride (Tedlar) bags. Two commercially available Tedlar bag models are studied. One is equipped with a polypropylene valve with integrated septum, the other with a dual port fitting made from stainless steel. Siloxane recovery in landfill gas samples is investigated as a function of storage time, temperature, surface-to-volume ratio and background gas. Recovery was found to depend on the type of fitting employed. The siloxanes sampled in the bag with the polypropylene valve show high and stable recovery, even after more than 30 days. Sufficiently low detection limits below 10 microg Nm(-3) and good reproducibility can be achieved. The method is therefore well applicable to biogas, greatly facilitating sampling in comparison with other common techniques involving siloxane enrichment using sorption media.

Project house water: a novel interdisciplinary framework to assess the environmental and socioeconomic consequences of flood-related impacts

Protecting our water resources in terms of quality and quantity is considered one of the big challenges of the twenty-first century, which requires global and multidisciplinary solutions. A specific threat to water resources, in particular, is the increased occurrence and frequency of flood events due to climate change which has significant environmental and socioeconomic impacts. In addition to climate change, flooding (or subsequent erosion and run-off) may be exacerbated by, or result from, land use activities, obstruction of waterways, or urbanization of floodplains, as well as mining and other anthropogenic activities that alter natural flow regimes. Climate change and other anthropogenic induced flood events threaten the quantity of water as well as the quality of ecosystems and associated aquatic life. The quality of water can be significantly reduced through the unintentional distribution of pollutants, damage of infrastructure, and distribution of sediments and suspended materials during flood events. To understand and predict how flood events and associated distribution of pollutants may impact ecosystem and human health, as well as infrastructure, large-scale interdisciplinary collaborative efforts are required, which involve ecotoxicologists, hydrologists, chemists, geoscientists, water engineers, and socioeconomists. The research network “project house water” consists of a number of experts from a wide range of disciplines and was established to improve our current understanding of flood events and associated societal and environmental impacts. The concept of project house and similar seed fund and boost fund projects was established by the RWTH Aachen University within the framework of the German excellence initiative with support of the German research foundation (DFG) to promote and fund interdisciplinary research projects and provide a platform for scientists to collaborate on innovative, challenging research. Project house water consists of six proof-of-concept studies in very diverse and interdisciplinary areas of research (ecotoxicology, water, and chemical process engineering, geography, sociology, economy). The goal is to promote and foster high-quality research in the areas of water research and flood-risk assessments that combine and build off-laboratory experiments with modeling, monitoring, and surveys, as well as the use of applied methods and techniques across a variety of disciplines.

Fouling mitigation in tubular membranes by 3D-printed turbulence promoters

Abstract Despite intensive research, fouling remains a severe problem in membrane filtration. It is often controlled by applying turbulent flow which requires a higher energy consumption. So-called turbulence promoters or static mixers can be inserted into the flow channel of tubular membranes. They deflect the fluid, induce vortices, enhance particle back-transport and increase the shear rate at the membrane surface, thus mitigating fouling. However, little is known how the geometry of such turbulence promotors affects the reduction of fouling. We investigate how different 3D-printed mixer geometries affect fouling and improve the flux during filtration with humic acid. Most mixer geometries used in the present study are based on a twisted tape; a Kenics static mixer is investigated as well. Static mixers with changing diameter prove to be less effective than twisted tape mixers with constant diameter which lead to an increase in permeate flux of around 130 % . The highest flux improvement of 140 % can be reached by applying a Kenics mixer. Regardless of their geometry, all investigated static mixer cause higher permeate fluxes at same specific energy consumption. Again, the Kenics mixer proves to be the most efficient static mixer. The presented mixer geometries can be fabricated with undercut injection molding techniques and represent a simple and viable option to make tubular membrane based filtration processes more efficient.

Temperature Enhanced Backwash

Decentralized drinking water treatment is limited by supply of service, consumables, spare parts and in particular, power. Therefore, gravity-driven dead-end ultrafiltration is applied to purify surface water with high suspended solid loading. To obtain high flux in the long term, an effective membrane backwash is mandatory. Also, disinfection and cleaning is required regularly. Here we propose a new process coping with these particular challenges in decentralized water production: Temperature Enhanced Backwash. Herein, the membrane is backwashed at elevated temperature and corresponding steam pressure. A mathematical description of the Temperature Enhanced Backwash reveals that membrane pores are filled predominantly with liquid phase, irrespectively of whether membranes are charged with saturated steam or boiling liquid. A steam - water mixture is discharged at the module outlet suggesting evaporation at the end of the pores. This evaporation at membrane - fluid interface supposedly creates high volume fluxes shearing off potential fouling layers. Combined with gravity-driven filtration, the overall process potentially can cope with highly intermittent electrical power supply or even its absence. The methodology shows competitive cleaning efficacy compared to mechanical backwashing as demonstrated experimentally using silica nanoparticles, humic acid and river water.