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High energy consumption is an important issue affecting the operation and development of wastewater treatment plants (WWTPs). This paper seeks energy-saving opportunities from three aspects: energy application, process optimization, and performance evaluation. Moreover, effective energy-saving can be achieved from the perspective of energy supply a...
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The current study focuses on understanding municipal wastewater constituents and assessing technological options to harness the energy content of wastewater in developing countries. There are numerous research studies related to water treatment technologies and wastewater energy value. However, it remains to be seen which perspectives actually make technology adoption feasible. This study explores and presents the potential for some viable and innovative municipal wastewater treatment plant (WWTP) systems as a paradigm shift towards resource recovery, energy neutrality, and the production of renewable energy by WWTPs. Various cost effective opportunities related to operational strategies, plant’ redesign, and the upgrading of current WWTPs that can foster self-reliant communities were visualized. Thermal (TH) and chemical pretreatments (CEPTs), sequential batch reactors (SBRs), anaerobic membrane fluidized bioreactors (MBR), Ammonia-Based Aeration Control (ABAC), and combined heat and power (CHP) systems can collectively contribute to energy recovery by WWTPs, with variability ranging from 85% to 111%. The study suggests that upgrading the system to become an energy self-reliant water treatment system outweighs the multimode costs associated with health and ecological damages by reducing diseases, pollution, and poor productivity regimes.
As the primary inorganic by-product species of ClO2, chlorite is believed to have negative toxicological effects on human health and therefrom greatly limits the wide application of ClO2 in water treatment. The synergistic trimethoprim (TMP) removal concerning degradation efficiency, energy consumption and disinfection by-products (DBPs) formation in the UV activated chlorite process accompanied by the simultaneously elimination of chlorite was comprehensively evaluated. UV/chlorite integrated process removed TMP far more rapidly than UV (1.52%) or chlorite (3.20%) alone due to the endogenous radicals (Cl•, ClO• and •OH), the contributing proportions of which were 31.96%, 19.20% and 44.12%. The second-order rate constants of TMP reaction with Cl•, ClO• and •OH were determined to be 1.75 × 1010, 1.30 × 109 and 8.66 × 109 M-1 s-1. The effects of main water parameters including chlorite dosage, UV intensity, pH as well as water matrixes (nature organic matter, Cl- and HCO3-) were examined. Kobs obeyed the order as UV/Cl2˃UV/H2O2≈UV/chlorite˃UV, and the cost ranking via electrical energy per order (EE/O, kWh m-3 order-1) parameter was UV/chlorite (3.7034) > UV/H2O2 (1.1625) ˃UV/Cl2 (0.1631). The operational scenarios can be optimized to achieve the maximum removal efficiencies and the minimum energy costs. The destruction mechanisms of TMP were proposed by LC-ESI-MS analysis. The overall weighted toxicity in subsequent disinfection was assessed as UV/Cl2>UV/chlorite > UV, the values of which in post-chlorination were 6.2947, 2.5806 and 1.6267, respectively. Owing to the vital roles of reactive chlorine species (RCS), UV/chlorite displayed far higher TMP degradation efficiency than UV, and concurrently presented much less toxicity than UV/Cl2. In an effort to determine the viability of the promising combination technology, this study was devoted to reduce and reuse chlorite and synchronously realize the contaminants degradation efficiently.
This review covers the technological measures of a self-sustainable anaerobic up-flow sludge blanket (UASB) system compared with an aerobic activated sludge process (ASP) for wastewater treatment plants (WWTPs). The ASP requires a huge amount of electricity and chemicals and also results in the emission of carbon. The UASB system, instead, is based on greenhouse gas (GHG) emission reduction and is associated with biogas production for cleaner electricity. WWTPs including the ASP system are not sustainable due to the massive financial power required for clean wastewater. When the ASP system was used, the amount of production was estimated to be 10658.98 tonnes CO2eq-d- of carbon dioxide. Whereas it was 239.19 tonnes CO2eq-d-1 with the UASB. The UASB system is advantageous over the ASP system as it has a high production of biogas, needs low maintenance, yields a low amount of sludge, and is also a source of electricity that can be used as a power source for the WWTPs. Also, the UASB system produces less biomass, and this helps in reducing costs and maintaining work. Moreover, the aeration tank of the ASP needs 60% of energy distribution; on the other hand, the UASB consumes less energy, approximately 3-11%.
The excess availability of wastewater and reduction in the energy resources has initiated a new thought process of ‘waste to energy’. The green technology like solar and wind system utilises natural unending resources for production of valuable energy. To utilise waste as a source of energy we require process that a convert the chemical energy trapped in waste to green energy. The conventional technologies like anaerobic digestor produce methane, but the purity of product and time duration taken for the production makes the system unsustainable. The new bio-electrochemical system has been rectified as a potential process that can utilise waste, produce valuable products and is being optimised towards sustainability. This chapter presents a comparative review with respect to this new technology and its ability for resource recovery.
The present special issue collected articles that address the very important topic of innovative approaches in water and wastewater treatment technologies. Thirteen articles are published, ten research paper and three review articles. The papers can be divided in four major categories, namely, membrane treatment, adsorption studies, advanced oxidation processes and wastewater treatment optimization. In the editorial, a brief description of the findings of each paper is presented along with a critical assessment.
The continuous reduction in water resource availability is one of the major global societal challenges. Wastewater treatment plants (WWTP) play an important role in this, as they can provide water recovery. Furthermore, effective sanitation services lead to a significant reduction of health risks and protect the environment. However, WWTPs consume large amounts of energy to comply with discharge standards. At the same time, wastewater contains resources, which can be recovered for secondary uses, if treated properly. This is particularly useful for rural South Africa where challenges associated with water-based pollution, declining nutrients and water shortage, require a paradigm shift. This involves the transition of wastewater treatment plants into water, sanitation and resource (nutrients and energy) recovery facilities, leading further to social, economic and environmental sustainability. This process will involve the implementation of engineering tools for predictive modelling of the waste resource recovery systems. This review identifies the conceptual need for such a systematic shift from wastewater treatment to waste recovery facilities in rural South Africa. The targeted impact is to promote and help the uptake of the conversion of wastewater treatment systems into low cost and environmentally sustainable water and resource recovery facilities. Overall, the outlook is positive for the future use of these systems in South-Africa.
The improvement of energy efficiency ensuring high nutrients removal is a great concern for many wastewater treatment plants (WWTPs). The energy balance of a WWTP can be improved through the application of highly efficient digestion or its intensification, e.g., through the introduction of the co-substrates with relatively high energy potential to the sewage sludge (SS). In the present study, the overview of the energetic aspect of the Polish WWTPs was presented. The evaluation of energy consumption at individual stages of wastewater treatment along with the possibilities of its increasing was performed. Additionally, the influence of co-digestion process implementation on the energy efficiency of a selected WWTP in Poland was investigated. The evaluation was carried out for a WWTP located in Iława. Both energetic and treatment efficiency were analyzed. The energy balance evaluation of this WWTP was also performed. The obtained results indicated that the WWTP in Iława produced on average 2.54 GWh per year (7.63 GWh of electricity in total) as a result of the co-digestion of sewage sludge with poultry processing waste. A single cubic meter of co-substrates fed to the digesters yielded an average of 25.6 ± 4.3 Nm3 of biogas (between 18.3 and 32.2 Nm3/m3). This enabled covering the energy demand of the plant to a very high degree, ranging from 93.0% to 99.8% (98.2% on average). Importantly, in the presence of the co-substrate, the removal efficiency of organic compounds was enhanced from 64% (mono-digestion) to 69–70%.
Hydrodynamic cavitation (HC) has been extensively studied for the Advanced Oxidation of organic compounds in wastewaters since it physically produces an oxidative environment at ambient conditions. This process is simple and economical since it can be realized through a properly designed restriction in a pipeline, even in retrofit solutions. Several experimental works individuated similar values of the optimal operating conditions, especially with regard to the inlet pressure. Up to now, the available modeling works rely on a single-bubble dynamics (SBD) approach and do not consider the actual process configuration and pollutant transport in proximity to the oxidizing environment. This work describes different experimental results (from this research group and others) and applies a novel mathematical model based on a transport-phenomena approach, able to directly simulate the effect of HC on the pollutant degradation. The novel proposed model is able to reproduce well a large number of experimental data obtained in different conditions, with different apparatus and different molecules, and allows to interconnect both SBD, fluid-dynamics, and physio-chemical variables in order to deeply study the interaction between the transport of pollutants and the reactive environment. This paper includes collection and discussion of several experimental results with the related main process parameters, description of the novel model and validation against the cited experimental results (to explain the effect of the operating pressure), sensitivity analysis, and the performance limit of the HC with the proposed modeling approach.
