Zbigniew Mucha

The use of multi-criteria analysis for selection of technology for a household WWTP compatible with sustainable development

Abstract This paper presents the use of multi-criteria analysis as a tool that helps choosing an adequate technology for a household wastewater treatment plant. In the process of selection the criteria of sustainable development were taken into account. Five municipal mechanical-biological treatment plants were chosen for the comparative multi-criteria analysis. Different treatment technologies, such as sand filter, activated sludge, trickling filter, a hybrid system - activated sludge/trickling filter and a hybrid constructed wetland system VF-HF type (vertical and horizontal fl ow) were taken into account. The plants’ capacities were 1 m3∙d-1 (PE=8) and they all meet the environmental regulations. Additionally, a solution with a drainage system was included into the analysis. On the basis of multi-criteria analysis it was found that the preferred wastewater treatment technologies, consistent with the principles of sustainable development, were a sand filter and a hybrid constructed wetland type VF-HF. A drainage system was chosen as the best solution due to the economic criteria, however, taking into consideration the primary (ecological) criterion, employment of such systems on a larger scale disagree with the principles of sustainable development. It was found that activated sludge is the least favourable technology. The analysis showed that this technology is not compatible with the principles of sustainable development, due to a lack of proper technological stability and low reliability. Streszczenie W pracy przedstawiono sposób wykorzystania analizy wielokryterialnej jako narzędzia pomocniczego do wyboru właściwego rozwiązania technologicznego przydomowej oczyszczalni ścieków. Przy wyborze uwzględniano kryteria zgodne z zasadami zrównoważonego rozwoju. Do porównawczej analizy wielokryterialnej wybrano 5 wariantów przydomowych, mechaniczno-biologicznych oczyszczalni ścieków. Porównywano systemy z filtrem piaskowym, z osadem czynnym, ze złożem biologicznym zraszanym, system hybrydowy - osad czynny ze złożem biologicznym oraz hybrydowy system hydrofi towy typu VF-HF (z pionowym i poziomym przepływem ścieków). Analizowano rozwiązania o przepustowości 1 m3∙d-1 (Równoważna Liczba Mieszkańców - RLM = 8), spełniające wymagania przepisów ochrony środowiska. Dodatkowo także rozwiązanie z zastosowaniem drenażu rozsączającego. Na podstawie analizy wielokryterialnej stwierdzono, że najbardziej korzystnymi rozwiązaniami technologicznymi, zgodnymi z zasadami zrównoważonego rozwoju, są systemy z filtrem piaskowym i hybrydowe systemy hydrofi towe typu VF-HF. Przy znacznej przewadze kryteriów ekonomicznych, jako najbardziej korzystne rozwiązanie wybrany został system z drenażem rozsączający, jednak biorąc pod uwagę kryterium nadrzędne (ekologiczne), aby zachować zasadę zrównoważonego rozwoju, należałoby wykluczyć możliwość stosowania tych rozwiązań na większą skalę. Stwierdzono, że najbardziej niekorzystnym jest rozwiązanie technologiczne z wykorzystaniem osadu czynnego. Wykonana analiza wykazała, że stosowanie tej technologii jest niezgodne z ideą zrównoważonego rozwoju. Jest to spowodowane brakiem odpowiedniej stabilności technologicznej i niewielką niezawodnością działania.

Long-term operation of Kickuth-type constructed wetland applied to municipal wastewater treatment in temperate climate

ABSTRACT The purpose of this paper is to discuss the problem of changes of effectiveness of Kickuth-type constructed wetland with subsurface flow applied to domestic wastewater treatment. This study is based on an example of a wetland 3000 m2 in surface, serving 800 inhabitants, located in Poland. The results of chemical analysis showed that after an initial year of ‘start-up time’, the efficiency of pollutant removal gradually increased to reach an apex in the 6th year of operation. Such maximum efficiency continued up to the 10th year of operation; afterwards it gradually dropped. Moreover, after 12 years of operation, a serious problem with overland flow was observed, which indicated the porous media clogging processes.

A simulation study of the energy-efficient options for upgrading and retrofitting a medium-size municipal wastewater treatment plant

ABSTRACT Many municipal wastewater treatment plants are retrofitted with membrane filtration that replaces secondary clarification. Such a solution saves space and improves overall treatment efficiency but at the cost of increased energy consumption and reduced potential for energy recovery from sewage sludge. Thus, the plant takes a step back from reaching energy self-sufficiency. In the presented case study, two alternative upgrade options were simulated for a medium-size municipal wastewater treatment plant in Poland: the first one assumed optimization of the existing bioreactor, and the other – installation of microfiltration membrane units inside the bioreactor. In both cases, anaerobic digestion of waste sludge with biogas utilization is planned. The results have shown that while under both upgrade options, the plants capacity can be effectively increased by approximately 50%, their effects on the plants energy balance will be very different. Although the installation of membrane modules accompanied by the construction of anaerobic digestion tanks improves the plants energy balance, it will remain negative. The option of optimizing the existing biological treatment system produces a positive energy balance with more energy produced from biogas than consumed. Thus, the plant is able to approach energy self-sufficiency. It has been concluded that retrofitting the plants with membrane filtration is not always the best option from the energy balance point of view and it should be preceded with a detailed analysis on a case-by-case basis.

Turbidity measurements as a tool of monitoring and control of the SBR effluent at the small wastewater treatment plant – preliminary study

Abstract The paper presents preliminary results of investigations on a relationship between turbidity and other quality parameters in the SBR plant effluent. The laboratory tests demonstrated a high correlation between an effluent turbidity and a total suspended solids (TSS) concentration as well as between TSS and COD. Such a relationship would help to continuously monitor and control quality of a wastewater discharge using turbidity measurement.

Wybór systemu usuwania i oczyszczania ścieków z wykorzystaniem analizy wielokryterialnej

The article describes the use of multi-criteria analysis to choose a solution removal system and wastewater treatment in the established agglomerations with a population of more than 10 000. Municipalities wishing to obtain funding for the expansion of the sewage system form the agglomeration of which all waste must be collected and treated in one or more high-efficiency wastewater treatment facility on their territory. It is also possible to transport wastewater to a larger plant. However, it requires carrying out technical and economic analysis taking also into account other equally important factors. The choice of disposal system and wastewater treatment in the urban area was based on sustainability criteria, using decision analysis. The proposed method can be used to choose the best variant disposal and wastewater treatment.

Threats of highly alkaline wastewater discharge to surface water

The paper discusses the discharge of highly concentrated alkaline wastewater from an industrial reservoir and its effect on surface waters. The discharge source is the Górka industrial reservoir, located in Trzebinia. The wastewater constitutes a threat to groundwater, which serves as a source of drinking water for surrounding villages. A detailed analysis of pH confirmed a high alkalinity of the tank content; the pH values were in the range of 12.5 to 13.5. Other water quality parameters (COD, sulfates, chlorides, TSS) were also very high. Initially, wastewater was discharged to the wastewater treatment plant (WWTP) in Chrzanów. Then, since the plant had refused further treatment due to operational disturbances, wastewater had to be discharged directly to the Chechło and Ropa creeks and finally to the Vistula river. A simultaneous monitoring of the water quality in these streams was provided. Wastewater discharged from the Górka reservoir was gradually diluted on its way to the Vistula river and therefore its impact on the Vistula river has been insignificant. The method turned out to be both effective and safe for the aquatic environment.