New German Guideline DWA-A 262 at Conference in Nantes
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.
Bavarian Innovation Award on Wastewater Treatment 2016
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)
First African Biogas Forum
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.