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Sustainable Wastewater Treatment Using Microalgae Technology
Published in Akinola Rasheed Popoola, Emeka Godfrey Nwoba, James Chukwuma Ogbonna, Charles Oluwaseun Adetunji, Nwadiuto (Diuto) Esiobu, Abdulrazak B. Ibrahim, Benjamin Ewa Ubi, Bioenergy and Environmental Biotechnology for Sustainable Development, 2022
Emeka G. Nwoba, John N. Idenyi, Christiana N. Ogbonna, James C. Ogbonna, Mathias A. Chia
The effluent from primary treatment is subjected to secondary treatment. The aim of secondary treatment is to use physical phase to remove settleable materials and biological process to remove suspended and dissolved organic compounds. After the secondary treatment, the water has some degree of effluent quality and is called secondary treated water. During secondary treatment, dissolved and colloidal compounds whose concentrations are determined by a measure of their biochemical oxygen demand are removed by the activities of microorganisms such as bacteria and protozoa that degrade biodegradable and soluble organic pollutants like sugars, fats and short-chain carbon compounds from various sources. Waste stabilization pond is the most widely used facility for secondary treatment of wastewaters.
Influence of the photoperiod on carbon dioxide, methane and nitrous oxide emissions from two pilot-scale stabilization ponds
Published in Juan Pablo Silva Vinasco, Greenhouse Gas Emissions from Ecotechnologies for Wastewater Treatment, 2021
Waste stabilization ponds (WSPs) are efficient, low-cost and low-tech options for sewage treatment mainly in developing countries (Arthur, 1983; Peña et al., 2002; Mara, 2005). WSPs use little or no electrical energy, are more appropriate than energy-intensive processes, such as activated sludge, and they are cheaper to construct, operate and maintain. However, WSPs may generate secondary negative environmental impacts because they may generate greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) related to the intrinsic metabolic processes that occur whilst achieving the desired degree of treatment (Van der Steen et al., 2003b).
Leachate Treatment
Published in Syed R. Qasim, Walter Chiang, Sanitary Landfill Leachate, 2017
In a stabilization pond, solids settle to the bottom. A wide variety of microscopic plants and animals find the environment a suitable habitat. Organic matter is metabolized by bacteria and protozoa as primary feeders. Secondary feeders include protozoa and higher animals such as rotifers and crustaceans. The nutrients released are utilized by algae and other aquatic plants. The main sources of oxygen are natural reaeration and photosynthesis. In the bottom layer, the accumulated solids are actively decomposed by anaerobic bacteria. Stabilization ponds are usually classified as aerobic, facultative, and anaerobic. This classification is based on the nature of the biological activity taking place. Design factors such as depth, detention time, organic loading, and effluent quality also vary greatly for the three types of lagoons. These values are provided in Table 9.5. Waste stabilization ponds have been widely used for sanitary sewage and dilute industrial wastes, mostly to provide final effluent polishing.
The design for wastewater treatment plant (WWTP) with GPS X modelling
Published in Cogent Engineering, 2020
In this wastewater treatment plant design, the characteristics of effluent of wastewater are adopted based on Iraqi National Standards for Discharge of Treated Municipal Wastewater to surface water courses. Based on these guidelines, the treatment processes must reduce BOD5 by more than 90%, ammonia by more than 80% and total nitrogen by more than 50% (nitrification/denitrification) (Marc et al., 2018). There are three specific treatment processes have been acknowledged as being feasible options for implementation, these are the Conventional Activated Sludge Process, Extended Aeration process and the Waste Stabilization process. Only the first two can meet the established effluent discharge criteria to River Tigris. The first process, mentioned to as the activated sludge/nitrification/denitrification process, is a conventional treatment process used successfully at sites in Iraq and throughout the world for treatment of domestic wastewaters. The second process, the Extended Aeration Activated Sludge system, although, now, commonly used in Iraq, is a well-known technology with less extensive sludge treatment requirements, which makes the capital and operational costs less than those required by the conventional activated sludge process. Waste Stabilization Ponds have the lowest capital and operational costs that can treat the domestic wastewater to the level that complies with the WHO and FAO guidelines for effluent reuse. Because this process is unable to meet the standards, so the extended aeration processes will be adopted for this purpose.
Combining planted drying beds to maturation ponds at pilot scale for a comprehensive treatment of faecal sludge in sub-Saharan Africa
Published in Environmental Technology, 2022
Ebenezer Soh Kengne, Wilfried Arsène Letah Nzouebet, Guy Valerie Djumyom Wafo, Pegui Douanla Maffo, Christian Wanda
Using two maturation pilot-scale ponds in series, the average removal performance of 73.07%, 83.86%, and 91.16% (2 log units) for faecal coliforms was obtained respectively at HRT4, 7, and 10 days. This was found to be lower than the results obtained by Garcia et al. [33] were a 99.98% (4 log units) reduction was obtained with a series of ponds treating domestic wastewater at 27.5 °C. In France and Spain, Gratziou and Chalatsi [37] reported a succession of anaerobic- facultative and 2 maturation ponds, a removal of 99.99 and 99.80% respectively. There was a significant difference (p< 0.05) between performances at the different HRT with the HRT 10 days having the highest removal, thus showing the positive effect of HRT on the removal efficiency. Such an effect of HRT on pond performances was already demonstrated by Von Sperling [29] and Crites et al. [28]. The removal of faecal bacteria is considered to be a much more complex mechanism involving interactions between the physical, chemical, and biological systems present in the lagoon [29,38]. Numerous mechanisms have been mentioned to be responsible for pathogen removal in waste stabilization ponds [12,28]. In this study, the temperature averaged 24°C, a value at which most chemical and biological factors that account for first order removal mechanism operate. Sunlight was also high during this study and might have contributed to the die-off of faecal bioindicators in the sense of Curtis [39]. However, the high algal density (7.4 × 107; 6.92 × 107; 7.94 × 107 cell.ml−1 respectively for 4,7 and 10 days HRT) as observed by Soh Kengne et al. [30], resulting in high SS (183.7, 79.55 and 117.75 mg.L−1 at HRT 4, 7 and 10 respectively) may have reduced the detrimental effect of solar radiations on pathogens. Nevertheless, Gray [40] argued that algal growth increases pH thus compensating for the reduced sunlight radiation within the pond. This argument could not be applied in this study since pH rarely exceeded 8. This could explain why faecal bioindicator removal in this study was lower than that obtained in design studies Mara [31] in maturation ponds (about 98%) as well as in sub-Saharan works [41]. Chemical processes such as oxidation of bacteria seemed to be more likely observed in this study than physical ones. The HRT positively affected the removal. For instance, 10 days of HRT was the most efficient retention time, corroborating Metcalf and Eddy [42] who considered HRT as a first order removal factor. Contrary to 30–60 days HRT recommended by Feachem [43] for a good removal in WSP, 10 days HRT at pilot scale presented a 2 log unit reduction for faecal coliforms, giving values that comply with both the MINEPDED [26] guidelines for discharge and the WHO [27] guidelines for safe reuse of wastewater and excreta in non-restricted agriculture. The reduced number of ponds giving comparable values with classical waste stabilization ponds (more ponds) constitutes the asset of this study as it helps reduce the footprints and investment cost of treatment plants.