Search

In this research capability of biological treatment method via active sludge and aquatic fern evaluated in different operating conditions and they were optimized in order to remove Zn (II). A simple reactor performance for treatment of model and real wastewater on laboratory and semi-industrial scale was investigated. This refining process proceeded with special attention to the effect of solution pH-value, pollutant concentration, absorbent concentration and reaction time. The batch semi-industrial scale reactor represented over 90 % removal efficiency under pH-value of 6 and 5-5.5 for aquatic ferns and active sludge, respectively. Effective reaction times represented various durations for aquatic ferns and active sludge with respect of 120 minutes and 90 minutes. The two biological masses had the best performances with 6 g/l for aquatic ferns and 5 g/l for active sludge. In the presence of 5 ppm of Zn (II) as the objective heavy metal, both absorbents had over 93.2 % removal efficiencies. While obviously laboratory-scale attempts introduced higher acceptable reduction efficiencies via this economic applicable treatment method. Additionally, economic considerations clarified feasibility of this recommended simple method.

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.

The necessary oxygen concentration for the biological process depends on the organic matter present in wastewater characterized by organic matter reaction rate with oxygen, k. This article highlights the impact of the reaction coefficient on oxygen dispersion in water. The first stage of the research led to the determination of the ratio between the coefficient of reaction and the coefficient of dispersion on the vertical of the tank as k/ez . [0.066 - 0.79]. Starting from this ratio, the specific oxygen flow required for the aeration process was determined to obtain a minimum oxygen concentration of 2 mg/L in the bottom zone of the tank: for k=3, specific gas flow qg=1.37 [m3/s*m], for k=0.2, qg=0.77 [m3/s*m] and for k=1.5, qg=1.03 [m3/s*m]. Value of gas flow rate has an important impact on reduction of the costs of wastewater treatment plants. This value has an important impact on the reduction of costs for wastewater treatment plants.

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).

The worldwide concerns have been raised for removal of heavy metals via environmentally friendly approaches. In this study biological removal of Fe metal ions from effluent was studied and individual effects of operating factors investigated in laboratory. Moreover effectiveness of non-living aquatic plants and activated sludge that used as bio-adsorbents was evaluated. Removal of heavy metal ions in batch reactors containing the laboratory and real effluent was carried out according to the results of pilot-scale optimization. Acidic environment with pH-value of 3.5 with 6 g/l Aquatic ferns had a removal efficiency of 81.2% while 5 g/l active sludge showed 78.2% performance. Also residence time of 90 and 120 minutes represented the best results for active sludge and aquatic ferns usage in removal of 50 ppm pollutant, respectively.

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.

Aerobic granular sludge technology can be one of the solutions to extend wastewater treatment plant when a limited space is available, besides Sequential Batch Reactor or biofilm carrier media technologies. This paper presents a comparative study between two types of technologies, Sequential Batch Reactor (SBR) and Granular Sequencing Batch Reactor (GSBR), using BioWin simulations based on the designed data of a wastewater treatment plant. Efficiencies of both technologies are studied regarding organic load and nutrients.

Sedimentation is one of the most important phenomena applied in wastewater treatment. The paper presents the CFD techniques used in teaching students the influence of the inlet baffle on the primary settling tank hydrodynamics. Different sizes and dimensions of the baffle are studied in order to highlight the optimum configuration that assures uniform flow in the settling area and prevents dead zones. By this mean the students have the possibility to evaluate multiple configurations in short time intervals and with low costs, when compared to hands-on experiments.

Teamwork skills become increasingly a pre-requisite for employment success. All employers want to recruit graduates who are able to cooperate, share ideas and knowledge, solve problems, quickly adapt to new situation and work in teams. Romanian educational system is mainly based on the individual study, but it has to adapt to this request. The paper presents two different extra curricular activities that were organized in University POLITEHNICA of Bucharest, Faculty of Power Engineering, in order to develop these skills on the students. The students had to work together two weeks to develop a project, but in one of them they worked without having to physically be together at all times, by using the internet as the main communication method. Both events involved students or young graduates from different countries. The Romanian students never had an experience like these before, they were very enthusiastic and they really appreciated the skills and knowledge gained in these events.

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.

In Romania, the hydropower is the main form of renewable source with an important share in energy mix. Despite their valuable advantages on supplying energy and balancing the energy system, public acceptance, environmental, social and economic impact has become a common challenge in development of hydropower projects. Increasing of water consumption and raising awareness regarding available water resources leads to an integrated management approach of them. In this paper the water footprint is estimated for one of the largest Romanian hydropower project, namely Hydropower Plant Vidraru. The water footprint from hydroelectricity is evaluated considering electricity production of the hydropower plant, water footprint of dam construction and three different approaches to quantify water footprint of the reservoir: gross water consumption, net water consumption and water balance. Also, water footprint is assessed based on economic value of the reservoir using allocation coefficients for various purposes of the reservoir. It is estimated that economic benefit of the reservoir is 81.92·106 €/y, with hydroelectricity major contributor.

The main goal of the wastewater treatment plant management consists in reducing the annual electricity costs by trying to supply the load demand using renewable energy sources (RES) (such as photovoltaic panels and biogas-based cogeneration engine). Based on real case measurements and carried on design process of the stochastic sources and cogeneration engine for covering the load demand, an optimization model is implemented to minimize the annual electricity costs. The model is tested on a characteristic day of each year season, under various load profile and intermittent sources production.