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Nowadays, the energy efficiency represents a general interest worldwide. The energy savings and increase of its intensity use constitutes a main objective in the development of urban communities. The wastewater treatment plants represent an important energy consumer in the existing power systems and focus is given on technological development of wastewater treatment plants and use of their output products, like sludge and biogas. The present paper deals with the energy optimization of a wastewater treatment plant located in the seaside, nearby a hotel complex, such that to achieve positive energy communities through better energy harvesting. The proposed optimization model minimizes the overall operating costs by using the biogas produced from the sewage plant and the photovoltaic installations within the area such that to obtain positive energy balance. The case study is carried on a wastewater treatment plant and hotel located in south-east of Romania, on the seaside.

In this paper carbon footprint is estimated for wastewater treatment plant Constanta South, Romania, by using a combined model from the available protocols for carbon footprint calculation. Off-site and on-site emissions were taken into account. The carbon footprint calculations were based on the operational data regarding power consumptions, sludge, chemicals and biogas production. A prediction for carbon footprint is done for upgrading wastewater treatment plant. For the current plant technology it is found that 0.44-0.54 kg CO2 eq have been released per cubic meter of treated wastewater for 2010-2013 years or 33.08-37.68 [kg CO2eq/PE and year]. For the upgraded plant, taking into account design data and the credit for biogas usage, it is found that the GHG emissions will be reduced at 0.17 kg CO2 eq per m3 treated wastewater or 32.33 [kg CO2eq/PE and year].

At European Union level, 10 million tons of sludge were generated per year as of 2008, 11.5 million tons recorded in 2015, with an expected rise to 13 million tons per year in 2020. Coupled with recent technological developments that have increased the efficiency of the processes through which biogas is obtained, the wastewater treatment industry has experienced increased competitiveness in sustainable developments. However, although the respective research field would benefit from the input of as many research centers as possible, the lack of highly specialized laboratories limits the participation of many actors. Finding a methodology for carrying out biochemical methane potential assays, that correlate the organic content of a substrate to a potential methane output, was thus targeted, with a focus on applicability in non-highly specialized laboratories. Such a procedure was determined through tests carried out for industrial and municipal wastewater applications, with a focus on the compatibility between the sludge and wastewater (inoculum and substrate).

Sustainable resource management is one of the world’s current challenges. Increasing of global population, economic growth, changes in lifestyle and habits, industry reforms and climate change have resulted in higher water and energy demand, leading to a competition between energy and water sector. Wastewater treatment plants (WWTPs) operators have to face with the problems related to reduce the energy consumption, but achieving process efficiency to comply with pollutants’ limitations set in legislation. Wastewater treatment generates significant amount of greenhouse gases (GHG). The carbon footprint of WWTP deeply depends on the technology and the size of the plant. To provide insight into the very close link between carbon footprint and power consumption, this paper presents an analysis of power consumption and carbon footprint during one year in eightujy WWTPs with different technologies for wastewater and sludge treatment.

Among the industries fundamental for modern life, wastewater treatment receives increasing interest for its potential to recuperate valuable resources. The biogas obtained through anaerobic digestion, more specifically, the methane it contains, often represents a powerful asset in operating a WWTP (wastewater treatment plant) economically. However, the microbiological processes that lead to obtaining methane are quite hard to model, and the results might not reflect the situations encountered during operation. One of the ways to estimate the methane yield of the substrate is based heavily on COD and its bioavailability. In this paper, an attempt was made to calibrate a more complex model to a situation where the extensive amount of data, usually required for accurate methane production estimations, is not available. The data obtained from simulations was compared to data obtained experimentally.

The energy used for biological process in a wastewater treatment plant depends on aeration equipment and hydraulic parameters in aeration tank. Gas bubbles flow into bioreactor determines an extra turbulence into the mixture. This paper presents the results obtained using the volume of fluid (VOF) mathematical model to determine the velocities generated by bubbles into an upward flow air-water mixture in a column of water. Also, it was identified vertexes center in the ascending air bubbles movement and the number and the diameter of the bubbles were determined. The theoretical results were compared to experimental and theoretical data from the literature and it was found a good correlation.