Overall, the framework conditions in South Africa for the generation of electricity from sewage gas are rather difficult. The remuneration for feed-in from renewable energies is fixed at auctions, this procedure prefers scalable technologies such as photovoltaics. Biogas, on the other hand, is limited by the availability of raw materials. This restriction applies in particular to the conversion of sewage and landfill gases into electricity. The unique selling point of biogas, simple storage and power generation at peak times, is also not affected by this process of auctioning.
Thus, the only economically decisive factor on the South African energy market is the savings in own electricity consumption. The current electricity prices of around 1.20 rand/kWh (around 0.08 €/kWh) are low by German standards. However, the electricity price has multiplied since 2007: at that time, it was 0.013 €/kWh. In addition, annual price increases of 10% have been announced.
In this field of tension AKUT was commissioned by the Deutschen Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH to prepare two studies on the use of sewage gas for the two sewage treatment plants Kingstonvalle and Zeekoegat.
Economic plus ecological advantages
Against the current background of water scarcity in Cape Town, the relevance and explosive nature of the topic becomes very clear. The lack of rainfall is primarily attributed to climate change. The studies therefore identify emission reductions, in this case reductions in methane emissions, as a significant advantage in addition to economic advantages. At present, the gas produced by sewage sludge digestion is released into the atmosphere without further measures. This is now to be changed so that the gas is collected, processed and used for power generation.
The studies present detailed comparisons of various technical components, operating models and organisational forms. In both sewage treatment plants, the economic benefit can be maximised by optimising the utilisation of the existing digestion towers. Capacity utilisation is to be increased by adding so-called co-substrates, either digested sludge from neighbouring sewage treatment plants or waste from the agricultural industry. The latter could be identified by local AKUT employees so that specific modelling could be carried out, taking into account both the biogas potential and transport costs.
Economically reasonable are also the variants with an exclusive treatment of the sewage sludge of the sewage treatment plant. However, the then lower investments will lead to a slight reduction in profitability.
In addition to the technical components and the various operational management, operator models from in-house operation to BOT models were also examined. Two preference variants were determined from six different operator models.
The decision now lies in the field of politics. Should the measures be implemented? Which of the preferred variants is preferred? GIZ and AKUT are ready to continue to support the City of Tshwane and Mbombela municipalities – both in decision-making and in technical implementation.
The international IWA conference on sustainable solutions for small water and wastewater treatment systems (s2small2017) was held October 22-26 in Nantes, France. Florent Chazarenc (IMT Atlantique) chairman of the conference emphasized that small systems play a significant role in solving problems of humanity: „Small is beautiful, efficient and affordable – small is the future“ he said. More than 200 participants responded to the call and discussed their proposals for solutions in the areas of resource-oriented sewage systems, wastewater treatment and recycling.
As a German contribution to the improvement of small sewage treatment plants Heribert Rustige, AKUT partner from Berlin, presented the new DWA worksheet A 262 on the topic of constructed wetlands. This guideline is expected to be published in November 2017 and replaces the previous A 262 from 2006, whereas many new solutions and system variants have been added to the new worksheet. This includes the so-called French system, which consists of a combination with raw wastewater pre-treatment in a planted gravel filter and post-treatment in a planted sand filter (e.g. Phragmifiltre). Another newly described method using active aeration is particularly innovative. It was developed by Scott Wallace in the USA and extensively tested on site for several years in Germany by the UFZ research institute in Leipzig.
International Interest in the German Constructed Wetland Guideline
In the past, the A 262 had already attracted interest from other countries. It was last translated into Russian. Many users are now waiting for the release of the current version. An English version will also be available soon from the DWA in Hennef.
The advantage of such a detailed set of rules is the increased safety for planners and operators. The worksheet specifies minimum requirements for the dimensioning of soil filters and refers to values derived from practical experience. The user must check in each case whether the boundary conditions are correct in his application. In doing so, the regulations focus on the treatment of domestic and municipal wastewater, including combined sewerage systems. In addition, the treatment of grey water in soil filters is also taken into account.
The tables, which describe, for example, the different wastewater compositions or specific design values, are helpful. Various useful combinations of processes are shown. However, Rustige emphasized in his speech that the guideline is not a simple construction manual, as it requires specialist knowledge. No design formulas or modeling approaches are shown because they have not yet proven themselves in practice.
What is more interesting is the presentation of minimum requirements with which certain effluent values or performance degrees can be achieved. In the theoretical modeling of treatment efficiency, it is often not taken into account that hydraulics or oxygen transfer rates can be decisive limiting factors, which in the worst case can lead to a total clogging of the soil filter. It is better to orientate oneself on the statistically relevant results derived from practice, as they are used in the A 262.
The municipality of Theres, Unterfranken, Bavaria, was awarded the Bavarian Innovation Prize 2016.The new groundbreaking concept for the replacement of an aged waste stabilization pond which was developed by AKUT will obtain a natural way of treatment combined with an inexpensive way of operation.
The innovative design for the combined sewage treatment comprises a raw wastewater filtration wetland in the first stage and a nitrification wetland as secondary treatment.
Energy efficient wastewater treatment
In her laudatory speech the Bavarian minister for environment, Ulrike Scharf, accentuated the pilot character of the system for Bavarian municipalities in the rural area. She praised the possibility of high quality treatment without the requirement of electrical energy supply.
Standard technical treatment systems need extra energy for aeration, motor driven actuators and pumping.
In this case flow through wetlands is solely driven by force of gravity. The key technical component for establishing intermittent flow to the optimized filtration wetlands is a self-regulating mechanical siphon. The two siphons are capable of transporting even raw wastewater with high flow rates to both treatment stages. By floating the filter surface within a short period of time the best distribution and a maximum of natural oxygen input is achieved. No extra energy for aeration (aerobe treatment and nitrification) is consumed. These siphons are robust and minimize operational work. A model of this siphon was demonstrated at the AKUT booth in Munich at IFAT 2016.
Innovative wetland systems substitute inefficient waste stabilization ponds
The treatment of combined sewage in constructed wetlands in Germany is a virgin territory. For this purpose we can rely on tremendous expertise of our French neighbours. More than 3,000 so called “French Systems” with two-stage raw wastewater treatment are serving French municipalities. These systems have successfully suppressed conventional stabilization ponds because of their very good overall performance and stable operation conditions. 20% of these systems treat combined sewage.
The DWA expert group on small treatment systems has intensively checked the French approach. Together with experts from the research institutes IRSTEA and UFZ main design criteria have been fixed for separate and combined sewage treatment. The minimum surface area for treatment is 2 and 2.5 m² respectively. By describing these systems in the revised guideline for design, construction and operation of constructed wetlands DWA-A 262 (draft April 2016) a new boost for wetland technology in Germany is expected.
Foto (left to right): Prof. Dr.-Ing. Jens Nowak (AKUT Berlin), Price winner Matthias Schneider (1. Mayor of Theres), Ulrike Scharf (Minister of Environment, Bavaria), Dipl.-Ing. Reinhard Müller (AKUT Hesse)
AKUT was prominently represented at the 1st African Biogas Forum in Nairobi.
The “African Biogas Forum” aimed to promote and support the sustainable development of the biogas sector in Africa, particularly Kenya. The Kenyan Cabinet Secretary Hon. Keter and the Deputy German Ambassador H.E. Deru launched the Forum. The event was supported by GIZ and the initiative “Renewables – Made in Germany” whose mission is to provide information upon the performance, efficiency and reliability of German renewable energy industry.
At our exhibition stand our Kenyan colleagues presented AKUT´s range of services in the areas of biogas, sewage and development cooperation. Additionally, our employee Mr. Dipl.-Ing. Romas Radtke gave a lecture about our various Kenyan projects: from the domestic small biogas plant via school energy stations with anaerobic digestion, wastewater treatment (aerobic / anaerobic) to industrial biogas plants, for example Kericho. The focus of his presentation was placed on the economics of small biogas plants and semi industrial biogas plants under the given economic conditions. He concluded that the production of biogas at most medium-sized farms with waste quantities of 5 to 15 tons per day was not economically feasible with the current fed-in tariffs. Exceptions to the rule are cases were the treatment of sewage / waste is in the foreground as biogas merely constitute an additional advantage here.
As a participant in the panel discussion “Biogas solutions”, Mr. Radtke presented various custom tailored solutions for AKUT´s customers illustrating our slogan “Customized Concepts for Environmental Technology”. Since 2006 AKUT is active on the Kenyan market. Intensive demand for an adjustment of the feed-in tariff for electricity from biogas has been emphasized. A working group of members of the biogas industry and customers is in charge to find solutions concerning this. The required increase to 15 US cents per kWh will allow a variety of projects that are not financially viable until now. Currently the market is limited only to customers with both: high volumes of waste and high energy demands as well. Through an appropriate feed-in tariff it will become more reasonable to produce power from biogas for the general market.
At the same time it became clear that the benefits of biogas in particular towards solar PV are not adequately addressed and promoted by policy makers.
It has been pointed out that compared to other Sub-Saharan African Countries the Kenyan market is already well developed – despite all limitations.
Starting in June 2016 our latest research project will investigate the benefits of various combinations of engineered treatment steps with constructed wetlands. In order to analyze additional elimination of trace organic compounds in the effluent of a wastewater treatment plant a pilot plant is going to be built at the wastewater treatment plant Schönerlinde (Berlin) in collaboration with Kompetenzzentrum Wasser Berlin (KWB – Berlin Centre of Competence for Water) and Berliner Wasserbetriebe (BWB). In this case an upstream ozonation stage will be combined with two different types of constructed wetlands. This combination has the objective to eliminate and reduce those persistent pharmaceutical residues which – without additional pre-treatment in wastewater treatment plants – would pass subsurface and surface flow treatment wetlands.
The project is part of a European research network named AquaNES. 30 partners in 10 countries will investigate on different focuses. Next to wastewater treatment systems the recycling of waters for drinking purposes through bank filtration and groundwater recharge are main components.
At the same time innovative measurement methods for quick detection of E.coli and antibiotic resistances shall be applied within the project. With new assessment methods and the development of decision-making tools including Life Cycle Assessment (LCA) and Ecosystem Services Analyses (ESA) planners and operators shall be supported.
At the first project meeting of all AquaNES participants, Valérie Bénard, Project Officer in the Environment & Resources Unit of the Executive Agency for Small and Medium-sized Enterprises (EASME), pointed out that high expectations are related to the project. After the ambitious and more than a year lasting procurement procedure with the identifier “Water-1b-2015” for innovative demonstration and pilot plants in the program Horizon2020 only 8 out of 160 proposals have been awarded and will be realized. The total budget of this project is going to be 10.7 million EUR, 73 % sourcing from public funding. The project is coordinated by Prof. Dr.-Ing. Thomas Wintgens, Institute for Ecopreneurship at the University of Applied Sciences and Arts Northwestern Switzerland.
Results of all sub-projects will be disseminated within the next three years (project timeframe until May 2019) in different publications which shall lead to broader application of best practices in the water sector.
AKUT is assigned to elaborate guidelines and manuals for planning and operation of well-functioning combinations of engineered wetlands with technical systems. Pilot plants of other partners are located in Rheinbach (Germany), Packington (England) and the Greek islands Antiparos and Thirasia.
From May 30 to June 3, 2016, our customers and business partners have the opportunity to meet us personally on the world`s leading fair for environmental technologies in Munich.
You find our exhibition booth in hall A 5 at the joint area of “Berlin Partner for Business and Technology” (booth No. 227/326). We are happy to present our latest products and innovations regarding treatment, recovery and drainage of rainwater and of wastewater from various sources (municipal, domestic and industrial). Once again this year’s focus is put on adapted, decentralized and small scale solutions in urban and rural areas.
A special highlight will be the live presentation of a self-priming siphon. This siphon works through hydraulic elevation (floating and sinking) without any external energy demand. A reliable start of a cycle doesn’t require auxiliary constructions and the siphon is designed for big amounts of potentially highly polluted sewage. This product may be an essential component of ideal solutions, e.g. in the reinforcement of sewage pond systems.
In order to fulfill latest requirements for the treatment of combined sewage most applied solutions are highly complicated in technological terms. The combination of a robust constructed wetland for combined sewage (regarding DWA-A 262, draft version 2016) with this siphon leads to optimized hydraulic efficiency whilst cleaning performance ranges from good to highly satisfying results. This solution makes it possible to comply with high requirements for the treatment of combined sewage. AKUT has developed this solution as an alternative to expensive and laborious network separation as the conventional solution for this challenge.
In case you are interested in these or similar, simple, cost-efficient and therefore (in the long run) sustainable solutions, we are happy to consult you at our corner booth No. 227/326 in hall A5.
We offer consultancy about our broad range of services, including the generation and capture of biogas out of domestic wastewater or organic substrates, energy saving and energy input of electricity and heat into semicentral grids, SBR technology as an upgrade of pond systems and last but not least sustainable sanitation systems (e.g. ECOSAN or NASS: DWA-A 272). You may feel free to arrange an appointment with us at IFAT beforehand. In this case we can issue entrance tickets to visit our stand. Contact us for appointments and tickets: 0049-30-52000950
In the framework of the program “Energetic utilization of urban waste – EnRes” AKUT has been awarded by the GIZ to develop concepts in the field of biogas generation out of sewage sludge. The timeframe of this project is approximately 2 years. AKUT collaborates in Mexico with its local partner engineering companies IBtech and UCY.
In addition to the elaboration of a manual for sewage gas utilization in wastewater treatment plants as well as to creating new teaching material for courses and workshops in this field a pilot project is going to be planned, implemented and evaluated. 8 out of 27 wastewater treatment plants with flow rates of more than 250 l/s have been selected for detailed assessment and investigation regarding economic and technological feasibility as a pilot project for sewage gas utilization. These studies shall be completed within the short timeframe of the project.
For further planning the wastewater treatment plants León, Colima and Paso Limón have been chosen. Plant designs shall be completed in the beginning of 2017.
Final workshop on rainwater harvesting in South Morocco
A circular path has been completed in order to present measures for strengthening the agricultural sector in the region Souss-Massa-Draâ in December 2015. Rainfalls are less frequent and single events often heavier in these oases that are highly affected by climate change.
Due to poor and infrequent water supply traditional agricultural activities have declined significantly and heavy rainfall events are cause of erosion in many areas. A combination of various decentralized and small-scale measures was set up to improve the situation. One example is the construction of several ground sills / small dams that have been built in the long branched valleys above the oasis Tidrheste to reduce erosion.
Water retention measures increase the infiltration rate and usable water is directed into small channels. As a result of the collection of water in Negarim microcatchments and decentralized cisterns the olive tree cultivation is now possible without usage of (scarce) groundwater.
The successful international cooperation of AKUT Umweltschutz Ingenieure Burkard und Partner, Schulze-Matthes Ingenieure, the Association Ennacer de Développement (AED) of Tidrheste and the GIZ shall be continued. Further information about the project, irrigation, erosion protection and Rainwater Harvesting in arid climate zones may be obtained from Heribert Rustige.
The 1,8 km long river arm “Kupergraben” in Berlin’s central district will be awakened after a deep sleep. The river arm will undergo renaturalization measures and parts of the section between Fischerinsel and the Bode Museum will be used as a swimming pool. The conversion will revitalize this UNESCO World Heritage Site as one of Berlin’s historic lifelines whilst the ecological rehabilitation of urban waters yields the way to a general sustainable urban transformation.
AKUT is assigned to draft and plan a pilot plant for a treatment of the river waters in a constructed wetland. AKUT will work on this assignment in cooperation with Dr.-Ing. Pecher und Partner Ingenieurgesellschaft mbH and Kompetenzzentrum Wasser Berlin gGmbh.
Final dimensioning and site-specific adaptions will be possible after different filter types (constructed wetlands) are analyzed in the pilot plant. Starting off with the construction of the plant in the first half of 2016, sampling and optimization is going to terminate in the end of 2018.
On behalf of GIZ in Brazil AKUT is commissioned to develop a new framework for improved energy efficiency in urban water supply systems.
Water resources management in Brazils is one of the sectors with a energy demand in relation to other public services. The water supply system is characterized by low efficiency. Supply systems are mostly outdated and in ailing condition.
The project is structured into four fields of activities: (1) support of the Brazilian Ministry of Cities (MCid) in developing new funding instruments with the goal of energy efficiency; (2) organization of interinstitutional and intersectoral dialogues; (3) Elaboration and application of technical and economical energy efficiency instruments and measures and (4) Extension and qualitative improvement of consultancy services for the water management sector concerning energy efficiency.
The project timeline is scheduled from beginning of 2016 until the end of 2018. AKUT has organized a close collaboration with the swiss engineers “Skat Consulting AG” (specialized on energy efficiency measures) and the Portuguese Laboratory for Civil Engineering (LNEC, Laboratório Nacional de Engenharia Civil) whose experience in the national initiative for loss control (iPerdas, Iniciativa Nacional para o Controle Eficiente de Perdas) will be essential for the success of this project.