Achieve Energy Neutrality Research Articles

High-rate aerobic and anaerobic technologies for carbon management and achieving energy neutrality

High-rate aerobic and anaerobic technologies for carbon management and achieving energy neutrality

Reverse flexing as a physical/mechanical treatment to mitigate fouling of fine bubble diffusers.

Achieving energy neutrality has shifted focus towards aeration system optimization, due to the high energy consumption of aeration processes in modern advanced wastewater treatment plants. A study on fine bubble diffuser fouling and mitigation, quantified by dynamic wet pressure (DWP), oxygen transfer efficiency and alpha was carried out in Blue Plains, Washington, DC. Four polyurethane fine bubble diffusers were installed in a pilot reactor column fed with high rate activated sludge from a full scale system. A mechanical cleaning method, reverse flexing (RF), was used to treat two diffusers (RF1, RF2), while two diffusers were kept as a control (i.e., no reverse flexing). There was a 45% increase in DWP of the control diffuser after 17 months of operation, an indication of fouling. RF treated diffusers (RF1 and RF2) did not show significant increase in DWP, and in comparison to the control diffuser prevented about 35% increase in DWP. Hence, reverse flexing potentially saves blower energy, by reducing the pressure burden on the air blower which increases blower energy requirement. However, no significant impact of the RF treatment in preventing a decrease in alpha-fouling (αF) of the fine pore diffusers, over time in operation was observed.

Strategies for achieving energy neutrality in biological nutrient removal systems - a case study of the Slupsk WWTP (northern Poland).

The paper presents a model-based evaluation of technological upgrades on the energy and cost balance in a large biological nutrient removal (BNR) wastewater treatment plant (WWTP) in the city of Slupsk (northern Poland). The proposed upgrades include chemically enhanced primary sludge removal and reduction of the nitrogen load in the deammonification process employed for reject water treatment. Simulations enabled to estimate the increased biogas generation and decreased energy consumption for aeration. The proposed upgrades may lead the studied WWTP from the energy deficit to energy neutrality and positive cost balance, while still maintaining the required effluent standards for nitrogen. The operating cost balance depends on the type of applied coagulants/flocculants and specific costs of electric energy. The choice of the coagulant/flocculent was found as the main factor determining a positive cost balance.

Towards energy neutrality by optimising the activated sludge process of the WWTP Bochum-Ölbachtal.

As a result of Ruhrverband's regularly performed energy audits the wastewater treatment plant (WWTP) Bochum-Ölbachtal shows substantial deficits concerning energy efficiency. Due to the energy consumption of internal recirculation, mixers and return activated sludge (RAS) pumping the existing pre-denitrification process configuration offers a specific energy consumption for biological treatment of 23 kWh (PE · a)(-1). In order to optimise the energy situation and to improve the treatment efficiency, the process layout was changed completely to a three-stage step-feed process. By optimising the hydraulic conditions, it was possible to reconstruct the plant with a free flow throughout the whole biological treatment system without any additional pumping. The total investment costs for this process scheme were 3.9 million €. These costs could be partly offset against the wastewater charge paid (2.9 million €). Compared to the overall energy consumption before the process modification, today the energy consumption for biological treatment amounts to 12.4 kWh (PE · a)(-1). The highest saving potential has been achieved by optimising mixing and reducing the energy demand for internal recirculation and RAS pumping. In the case of the WWTP Bochum-Ölbachtal, the modification of the treatment process not only results in an improved energy situation but also increased the treatment efficiency in such a way that the nitrogen concentration in the effluent could be constantly kept below 5 mg L(-1) N(tot), which provides the basis for being exempted from the wastewater discharge for nitrogen. As a result of all these measures, the rate of self-sufficiency by using biogas from the digester in combined heat and power units has been increased substantially from 60% before process modifications to 97%. With the upcoming optimisation measures, a further increase of self-sufficiency is expected to finally achieve energy neutrality based on yearly averages. The example of the WWTP Bochum-Ölbachtal clearly shows that it is worthwhile to consider further measures for improving the energy and treatment efficiency, although most of the machinery was not fully depreciated at the time of implementing the new concept. It is also evident that the regular energy monitoring is essential for identifying potential for improvement. In this context and based on Ruhrverband's experience, it is highly suggested that energy audits are performed regularly for larger WWTPs.

Effects of dissolved organic matters (DOMs) on membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater

Anaerobic membrane bioreactors (AnMBRs) have been regarded as a potential solution to achieve energy neutrality in the future wastewater treatment plants. Coupling ceramic membranes into AnMBRs offers great potential as ceramic membranes are resistant to corrosive chemicals such as cleaning reagents and harsh environmental conditions such as high temperature. In this study, ceramic membranes with pore sizes of 80, 200 and 300 nm were individually mounted in three anaerobic ceramic membrane bioreactors (AnCMBRs) treating real domestic wastewater to examine the treatment efficiencies and to elucidate the effects of dissolved organic matters (DOMs) on fouling behaviours. The average overall chemical oxygen demands (COD) removal efficiencies could reach around 86–88%. Although CH4 productions were around 0.3 L/g CODutilised, about 67% of CH4 generated was dissolved in the liquid phase and lost in the permeate. When filtering mixed liquor of similar properties, smaller pore-sized membranes fouled slower in long-term operations due to lower occurrence of pore blockages. However, total organic removal efficiencies could not explain the fouling behaviours. Liquid chromatography-organic carbon detection, fluorescence spectrophotometer and high performance liquid chromatography coupled with fluorescence and ultra-violet detectors were used to analyse the DOMs in detail. The major foulants were identified to be biopolymers that were produced in microbial activities. One of the main components of biopolymers – proteins – led to different fouling behaviours. It is postulated that the proteins could pass through porous cake layers to create pore blockages in membranes. Hence, concentrations of the DOMs in the soluble fraction of mixed liquor (SML) could not predict membrane fouling because different components in the DOMs might have different interactions with membranes.

Adaptive control of the packet transmission period with solar energy harvesting prediction in wireless sensor networks.

A number of research works has studied packet scheduling policies in energy scavenging wireless sensor networks, based on the predicted amount of harvested energy. Most of them aim to achieve energy neutrality, which means that an embedded system can operate perpetually while meeting application requirements. Unlike other renewable energy sources, solar energy has the feature of distinct periodicity in the amount of harvested energy over a day. Using this feature, this paper proposes a packet transmission control policy that can enhance the network performance while keeping sensor nodes alive. Furthermore, this paper suggests a novel solar energy prediction method that exploits the relation between cloudiness and solar radiation. The experimental results and analyses show that the proposed packet transmission policy outperforms others in terms of the deadline miss rate and data throughput. Furthermore, the proposed solar energy prediction method can predict more accurately than others by 6.92%.

Sustainable wastewater treatment – ways to achieve energy neutrality

Increasing emission of greenhouse gases intensifies global warming. To tackle the problem, major economies in the world need to implement policy on energy saving. The wastewater treatment industry, being one of the energy consumers, has developed various technologies to improve energy efficiency and has started to use renewable energy with the aim of achieving energy neutrality in the wastewater treatment process. A literature review found that there is a series of energy-saving methods that can reduce the electricity consumption by 20% in wastewater treatment. Majority of the energy saving comes from energy conservation measures in pumping and aeration systems. In wastewater treatment works, two kinds of renewable energy are usually available, namely solar energy and biogas. The recent development of photovoltaic cells makes it a more practical and financially viable energy source which may cover 40% of the electricity consumption of a wastewater treatment works. Biogas, a by-product generated from the anaerobic digestion process in a wastewater treatment works, can also generate 40% of the electricity required. To achieve energy neutrality, the remaining electricity consumption can be generated through co-digestion of wastewater sludge and organic fraction in municipal solid waste.

Eco-Friendly Buildings: the central factor in transitioning to a Green Economy

The building sector is the largest contributor to global greenhouse gas emissions. More than 33% of global energy use is consumed in offices, homes, and other buildings. This figure is expected to double to more than 60% by 2030. It is a vital requirement, therefore, that new construction projects and renovations to existing construction, are focused on eco-friendly building designs. Such consideration is a low-cost means to battling climate change, reducing energy bills, and diminishing our reliance on fossil fuels. However, a failure to act immediately will compound and multiply the costs associated with climate change. This paper will present building designs and techniques, the goal of which will be to achieve energy neutrality. That is to say that the building’s energy demand will be offset by power generated from renewable energy sources. For instance, in a country such as the UAE, there are high numbers of sunshine hours and a considerable amount of wind potential. It would therefore be best to incorporate solar panels into new building designs. Micro wind turbines, distributed in an aesthetically pleasing way, could supplement the solar panels. Many factors need to be considered when creating an energy efficient building in such a sunny climate. These include: making the best technical use of local resources to avoid the costly (financially and ecologically) long-distance transportation of construction materials; determining the most optimum balance between harnessing the natural sunlight and insulating the inside of the structure from its accompanying heat; and creating natural ventilation and air filtering through design rather than focusing on energy draining air conditioning systems. Of these three, the last may be the most important, as the highest percentage of household energy consumption is associated with cooling/heating living spaces and with heating water. These are two aspects that greatly affect quality of life and that people will not forsake. Their ecological adaptation is therefore necessary in order for populations to adopt more sustainable lifestyles. The focus of this paper will then be about balance: balancing the planet’s and our communities’ future needs with sustainment of home comforts and quality of life. Balance of future urban development with the ecological integrity of our land and water. Balance of ecological building design with natural resource capitalisation. A balance between people and nature. This paper will explore how these goals can be realised through concepts such as incorporation of renewable energies into design; green rooftops; holistic and life cycle approaches to consumption, waste, and recycling; reduced traffic through intelligent pedestrian community design; means of renewable energy transportation; and the reduction of urban heat island effect.

Building Integrated Photovoltaics (BIPV): Review, Potentials, Barriers and Myths

AbstractTo date, none of the predictions that have been made about the emerging BIPV industry have really hit the target. The anticipated boom has so far stalled and despite developing and promoting a number of excellent systems and products, many producers around the world have been forced to quit on purely economic grounds. The authors believe that after this painful cleansing of the market, a massive counter trend will follow, enlivened and carried forward by more advanced PV technologies and ever-stricter climate policies designed to achieve energy neutrality in a cost-effective way. As a result, the need for BIPV products for use in construction will undergo first a gradual and then a massive increase. The planning of buildings with multifunctional, integrated roof and façade elements capable of fulfilling the technical and legal demands will become an essential, accepted part of the architectonic mainstream and will also contribute to an aesthetic valorisation. Until then, various barriers need to be overcome in order to facilitate and accelerate BIPV. Besides issues related to mere cost-efficiency ratio, psychological and social factors also play an evident role. The goal of energy change linked to greater use of renewables can be successfully achieved only when all aspects are taken into account and when visual appeal and energy efficiency thus no longer appear to be an oxymoron.