Wastewater Treatment 37 German research underway on trickling filter practices

Trickling filter technology is one focus of a joint research project – EXPOVAL – funded by the German government that will validate engineering guidelines and optimum conditions for achieving high performance. Dr. Christian-Dominik Henrich of GEA 2H Water Technologies Gmbh reports.

Poor wastewater treatment is one of the biggest ventilation openings at the bottom of the filter, clogging in conventional, stone-packed trickling enemies of a safe and sustainable water supply through which air can freely flow. The media is filters, along with a poor understanding of all over the world. Next to frugal handling placed onto a substructure usually made out of nutrient removal characteristics and poor of existing water resources, the treatment of parallel beams placed on concrete feet. Originally, modeling of actual processes inside trickling wastewater, sometimes towards future reuse, is trickling filters were packed with a stone or filters – led to a decline in the use of trickling important. Unfortunately, the elusive effects of lava filling. Now, these filters are packed with filters. improving water supply through groundwater plastic media – first made out of thermoformed Because of the newly developed plastic recharge or surface water must be weighed polyvinyl chloride (PVC) sheets glued to media, as well as the increased importance against capital cost, cost of energy demand, and structured packings, and later made out of the of sustainability, the trickling filter is other variable costs of wastewater treatment more environmentally friendly polypropylene going through a renaissance. Especially in facilities. With the costs per unit of energy corrugated sheets that are not glued but welded combination with other unit operations such constantly rising, it is of utmost importance together to structured packings. as anaerobic pre-treatment and optimized that future wastewater treatment is energy- Until the 1980s, trickling filters were promoted process design, these new-generation trickling efficient. Important considerations, especially in the western hemisphere as an energy-efficient filter systems are able to treat wastewater to in developing countries, should include the process for using microbial systems to treat very high standards, while offering low energy reliability and simplicity of a wastewater wastewaters. In those areas, the only need for demand and a high degree of simplicity and treatment process. Low-maintenance unit energy was to lift effluent by pumping it for robustness. Because of these improvements new operations ensure a continuous treatment of distribution on top of the filter. Pumping costs trickling filter projects are being implemented incoming wastewater. were reduced by using hillsides for gravitational all over the world, many of them receiving A trickling filter is a fixed-growth biofilm flow. The main difference between trickling funding from institutions such as the KfW treatment system where the wastewater trickles filters and an activated sludge system is in oxygen Development Bank in Germany, which focuses through a media on which a biofilm grows. supply. In trickling filters, oxygen demand is on sustainable development. The wastewater is distributed at the top of the often satisfied by natural ventilation without With the new generation trickling filter filter, with the use of rotating distributor arms any need for energy-intensive aeration and high- technology and an intelligent plant design and that can be either hydraulically or electrically tech equipment. However, increasing effluent operation, high flexibility is achievable. This driven. Oxygen is provided to the system through demands and process issues – such as media includes the ability to treat waters to effluent

Until the 1980s, trickling filters were promoted in the western hemisphere as an energy- efficient process for using microbial systems to treat wastewaters.

Right: Trickling filter pilot plant at Warsan Sewage Treatment Plant in Dubai, United Arab Emirates.

World Water September/October 2014 38 Wastewater Treatment

Partnership explores biofilm process efficiency

A partnership between Cranfield University in scale investigations of alternative design the United Kingdom and Warden Biomedia, a approaches. The project will be structured UK manufacturer of filter media for aerobic across six research phases, culminating in a wastewater treatment, will focus research and final thesis towards the end of 2017. Dr. Ana development efforts on biofilm processes with Soares, lecturer in biological engineering and the aim to improve the efficiency, cost- water program director, will supervise the effectiveness, and sustainability of process project. units such as submerged aerated filter, Dr. Soares commented, “Collaboration moving bed biofilm reactor, and trickling filters. between industry and academia is crucial for a Warden Biomedia manufactures five project such as this. We are able to address different types of random filter media, fundamental questions and universal laws of If the findings are injection-molded in polypropylene, with water science, but we are also able to study specific design features to increase the how these apply and their implications across confirmed, a efficiency of the biological process. “This wastewater treatment applications. reliable calculation approach to wastewater treatment holds “There are important pressures and drivers much greater potential than is currently being within the wastewater treatment industry, such algorithm for the harnessed,” said Managing Director Mark as the need to reduce energy consumption, Barrett. The company is sponsoring this and the requirements of various regulatory optimal sizing of postgraduate research project to provide a frameworks. A partnership of this type enables trickling filter foundation for the next generation of biofilm us to consider all aspects of the process to processes, he explained. develop more effective solutions.” systems under Cranfield University Water Science Institute This partnership marks Warden Biomedia’s different climatic will supervise the research. Operating in this first sponsorship of postgraduate research. field of research for almost 40 years, the Barrett says the research will provide a deeper conditions can be Institute employs 15 academics with understanding of the science at the heart of defined. significant expertise in water processes. these aerobic processes, which will help to Cranfield is a postgraduate-only university, determine where best to focus the company’s working in close collaboration with industry investments in product development. He and all of its 60 PhD students have industrial added, “Our biomedia range offers significantly sponsors. improved performance over alternative media, The project will begin with an MSc thesis while the traditional alternative is to use natural due to be completed by postgraduate student aggregates, from quarrying or dredging, or blast Joana Manuel Silva Dias. Next, a PhD project furnace clinker, which have limitations in terms on the design, operation, and efficiency of of sustainability and availability.” Another biofilm processes will analyze existing full-scale advantage is that they are manufactured in process units that use Warden’s Biomedia. It recycled polypropylene, reusing plastics that will also involve laboratory, pilot and active, would otherwise go to landfill. quality comparable to activated sludge (AS) and the prevailing conditions there compared to In that study, the cleaning performance of a semi- activated sludge biological nutrient removal other climates, specifically to higher or lower industrial trickling filter pilot plant was examined (AS-BNR) processes. Additionally, these filters wastewater temperatures. The focuses of the at high temperatures of wastewater and air in can provide the ability to produce a variety of study are on municipal wastewater treatment laboratory conditions. It is the goal of the current effluents that are treated to meet specific local procedures. These include the activated sludge study to validate the results and conclusions needs during seasonal variations at very low process (which includes compressed aeration through practice. If the findings are confirmed, operational and maintenance costs. systems), the trickling filter process, anaerobic a reliable calculation algorithm for the optimal Unfortunately, existing engineering guidelines treatment and wastewater ponds, wastewater sizing of trickling filter systems under different are primarily based on research that was disinfection and recycling or treating the climatic conditions can be defined. done long ago, when stone-filled trickling sewage sludge. Six German universities and 11 For the validation, five plants – in Namibia on filters were standard. Here, many operational industrial partners are involved in the more than the African continent; Georgia; Albania; Dubai, recommendations and design equations or four-year project – including GEA 2H Water United Arab Emirates; and Nicaragua in Central constants cannot be directly transferred to new Technologies, together with the University of America – were selected. These plants cover the generation trickling filters filled with structured Stuttgart, which are examining the trickling full range of technical and climatic conditions. packings. Additionally, these guidelines were filter processes specifically. They are in different climate zones and each developed for standard western climate zones This project will provide, among other things, operates one or more trickling filters. In addition, at moderate temperatures. Hence, when using a new directive from the German Association the selected plants, with the exception of Dubai, these old design equations for filters located in for Water Management, Wastewater and Waste are in regions where there is a lack of energy hot or cold climates, these filters are vastly over- (DWA) for consulting engineers that considers and infrastructure. Additionally, two 6-meter- or under-designed. country-specific factors, such as wastewater diameter trickling filter pilot plants were erected In 2012, the joint project EXPOVAL (the and air temperatures, inlet and outlet values in Dubai – filled with polypropylene structured name taken from the study’s title, “Export- and higher salinities. This directive will serve packing to investigate carbonaceous material oriented research and development in the as a practical resource that enables engineers removal and separate or combined nitrification. field of wastewater – validation of technical to make a well-founded decision as to under The results of this research project will be fully facilities”) began as a part of the funding which conditions the trickling filter process investigated and the resulting DWA directive will focal point of sustainable water management offers benefits compared to other methods. The be published in early 2016. (NaWaM). Seventy-seven percent of the project document will also provide specific sizing and – a total of US$9.71 million – is financed by the operating information. Author’s Note German Federal Ministry for Education and The scientific and theoretical foundations Dr. Christian-Dominik Henrich is a process Research (BMBF). The study’s main goal is to were already created in the previous project, specialist at GEA 2H Water Technologies expand the dimensioning approaches that apply “Export-oriented research and development in GmbH, based in Hürth, Germany. Contact the in Germany, and that are only directed toward the field of water supply and sewage disposal.” author by email at: [email protected].

September/October 2014 World Water