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"ACTIVATED SLUDGE"
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Photo-Activated Sludge : a novel algal-bacterial biotreatment for nitrogen removal from wastewater
Ammoniumrijk afvalwater wordt veelal geproduceerd door gemeentelijk, industrieel en landbouwafval, en effluent uit anaerobe afvalwaterzuiveringsmethoden. Dit vormt een risico voor het milieu vanwege de hoge concentratie aan voedingsstoffen (stikstof en fosfor), wat eutrofièering in waterpartijen kan bevorderen en daarmee de kwaliteit van ecosystemen kan aantasten. Als innovatieve oplossing hierop is een nieuw biologisch verwerkingsmechanisme genaamd Photo-Activated Sludge (PAS) geèevalueerd, wat gebruik maakt van een consortium van microalgen en bacterièen voor de zuivering van ammoniumrijk afvalwater.
Book
Anticipating the next century of wastewater treatment
Advances in activated sludge sewage treatment can improve its energy use and resource recovery Rapid urbanization and industrialization in the 19th century led to unhealthy environments and wide-spread epidemic diseases. In response, research was undertaken that led to the development of sanitation technology. Exactly 100 years since the activated sludge process was presented ( 1 ), it is still at the heart of current sewage treatment technology. Activated sludge is a mixture of inert solids from sewage combined with a microbial population growing on the biodegradable substrates present in the sewage. The settling and recycling of sludge inside treatment plants was the invention of Ardern and Lockett. The current demands from a rapidly growing human population and the need for a more sustainable society are pushing forward new developments for sewage handling. These developments have two main drivers: general process improvements and the contribution to the recycling of resources ( 2 , 3 ).
Journal Article
Synthesis of metal-doped nanoplastics and their utility to investigate fate and behaviour in complex environmental systems
Research on the distribution and effects of particulate plastic has intensified in recent years and yet, due to analytical challenges, our understanding of nanoplastic occurrence and behaviour has remained comparatively elusive. However, process studies could greatly aid in defining key parameters for nanoplastic interactions within and transfers between technical and environmental compartments. Here we provide a method to synthesize nanoplastic particles doped with a chemically entrapped metal used as a tracer, which provides a robust way to detect nanoplastics more easily, accurately and quantitatively in complex media. We show the utility of this approach in batch studies that simulate the activated sludge process of a municipal waste water treatment plant and so better understand the fate of nanoplastics in urban environments. We found that the majority of particles were associated with the sludge (>98%), with an average recovery of over 93% of the spiked material achieved. We believe that this approach can be developed further to study the fate, transport, mechanistic behaviour and biological uptake of nanoplastics in a variety of systems on different scales.Analytical challenges in detecting nanoplastics have hindered the understanding of their behaviour in environmental systems, but these difficulties can be circumvented by synthesizing metal-doped nanoplastics (where the metal can be measured as a proxy for the plastic) to undertake mechanistic investigations of particle fate, transport and biological interactions in lab and pilot-scale studies.
Journal Article
The Advancement in Membrane Bioreactor (MBR) Technology toward Sustainable Industrial Wastewater Management
The advancement in water treatment technology has revolutionized the progress of membrane bioreactor (MBR) technology in the modern era. The large space requirement, low efficiency, and high cost of the traditional activated sludge process have given the necessary space for the MBR system to come into action. The conventional activated sludge (CAS) process and tertiary filtration can be replaced by immersed and side-stream MBR. This article outlines the historical advancement of the MBR process in the treatment of industrial and municipal wastewaters. The structural features and design parameters of MBR, e.g., membrane surface properties, permeate flux, retention time, pH, alkalinity, temperature, cleaning frequency, etc., highly influence the efficiency of the MBR process. The submerged MBR can handle lower permeate flux (requires less power), whereas the side-stream MBR can handle higher permeate flux (requires more power). However, MBR has some operational issues with conventional water treatment technologies. The quality of sludge, equipment requirements, and fouling are major drawbacks of the MBR process. This review paper also deals with the approach to address these constraints. However, given the energy limitations, climatic changes, and resource depletion, conventional wastewater treatment systems face significant obstacles. When compared with CAS, MBR has better permeate quality, simpler operational management, and a reduced footprint requirement. Thus, for sustainable water treatment, MBR can be an efficient tool.
Journal Article
Mathematical Modelling and Computer Simulation of Activated Sludge Systems
This book provides, from the process engineering perspective, a comprehensive and up-to-date overview regarding various aspects of the mechanistic (\"white box\") modelling and simulation of advanced activated sludge systems performing biological nutrient removal. In the new edition of the book, a special focus is given to nitrogen removal and the latest developments in modelling the innovative nitrogen removal processes. Furthermore, a new section on micropollutant removal has been added.The focus of modelling has been shifting in the last years to models that can describe the performance of a whole plant (plantwide modelling). The expanded part of this new edition introduces models describing the most important processes interrelated with the mainstream activated sludge systems as well as models describing the energy balance, operating costs and environmental impact. The complex process evaluation, including minimization of energy consumption and carbon footprint, is in line with the present and future wastewater treatment goals.By combining a general introduction and a textbook, this book serves both intermediate and more experienced model users, both researchers and practitioners, as a comprehensive guide to modelling and simulation studies. The book can be used as a supplemental material at graduate and post-graduate levels of wastewater.
eBook
Activity enhancement of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in activated sludge process: metabolite reduction and CO2 mitigation intensification process
The interaction of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) is of considerable importance in nitrification process. Ecophysiological interactions between the communities of AOB and NOB were investigated by monitoring NO2− as the intermediate compound in an organic carbon-depleted nitrifying activated sludge fed only NH4+ as a nitrogen source (40 mg/L). The presence of boom and bust (feast and famine) cycle successfully indicates the activity cycles of AOB and NOB through cultivation-dependent method. The maximum growth rate and yield for AOB in nitritation-dominant period were (0.67 day−1, 0.17 gVSS gN−1) and for NOB in nitratation-dominant period were (0.71 day−1, 0.072 gVSS gN−1). Soluble microbial products (SMP) and extracellular polymeric substances (EPS) generated by AOB were 1.2 and 1.8 mg/L, respectively, while NOB produced 0.6 mg/L of SMP and 1 mg/L of EPS. While NOB were low in utilization-associated products (UAP) (0.07 mg/L) and biomass-associated products (BAP) (0.12 mg/L), AOB were higher in UAP (0.15 mg/L) and BAP (0.3 mg/L). The continuation presence of zero C/N ratio, in either inlet ratio or net available ratio for the microbial community, can prolong and enhance nitratation process. NOB enrichment and nitratation intensification strategy through zero C/N ratio are able to reduce remarkably microbial metabolites 50% lower than conventional process and enhance nitrification efficiency in activated sludge-involved processes.
Journal Article
COD capture: a feasible option towards energy self-sufficient domestic wastewater treatment
Although the activated sludge process, one of the most remarkable engineering inventions in the 20
th
century, has made significant contribution to wastewater reclamation in the past 100 years, its high energy consumption is posing a serious impact and challenge on the current wastewater industry worldwide and is also inevitably linked to the issue of global climate change. In this study, we argued that substantial improvement in the energy efficiency might be no longer achievable through further optimization of the activated sludge process. Instead, we should devote more effort to the development or the adoption of novel treatment configurations and emerging technologies. Of which an example is A-B process which can significantly improve the energy recovery potential at A-stage, while markedly reduces energy consumption at B-stage. Various configurations of A-B process with energy analysis are thus discussed. It appears highly possible to achieve an overall energy gain in WWTPs with A-B process as a core.
Journal Article
Carbon capture for blackwater: chemical enhanced high-rate activated sludge process
Blackwater has more benefits for carbon recovery than conventional domestic wastewater. Carbon capture and up-concentration are crucial prerequisites for carbon recovery from blackwater, the same as domestic wastewater. Both chemical enhanced primary treatment (CEPT) and high-rate activated sludge (HRAS) processes have enormous potential to capture organics. However, single CEPT is subject to the disruption of influent sulfide, and single HRAS has insufficient flocculation capacity. As a result, their carbon capture efficiencies are low. By combining CEPT and HRAS with chemical enhanced high rate activated sludge (CEHRAS) process, the limitations of single CEPT and single HRAS offset each other. The carbon mineralization efficiency was significantly influenced by SRT rather than iron salt dosage. An iron dosage significantly decreased chemical oxygen demand (COD) lost in effluent. Both SRT and iron dosage had a significant influence on the carbon capture efficiency. However, HRT had no great impact on the organic mass balance. CEHRAS allowed up to 78.2% of carbon capture efficiency under the best conditions. The results of techno-economic analysis show that decreasing the iron salt dosage to 10 mg Fe/L could promise profiting for blackwater treatment. In conclusion, CEHRAS is a more appropriate technology to capture carbon in blackwater.
Journal Article
Bacterial community and filamentous population of industrial wastewater treatment plants in Belgium
The discharge of industrial water requires the removal of its pollutants, where biological wastewater treatment plants (WWTPs) are the most used systems. Biological WWTPs make use of activated sludge (AS), where bacteria are responsible for the removal of pollutants. However, our knowledge of the microbial communities of industrial plants is limited. Understanding the microbial population is essential to provide solutions to industrial problems such as bulking. The aim of this study was to identify at a high taxonomic resolution the bacterial population of 29 industrial WWTPs using 16S rRNA amplicon sequencing. Our results revealed that the main functional groups were dominated by
Thauera
and
Zoogloea
within denitrifiers,
Dechloromonas
in phosphate-accumulating organisms, and
Defluviicoccus
in glycogen-accumulating organisms. The activated sludge characterization indicated that 59% of the industrial plants suffered from bulking sludge, with DSVI values of up to 448 mL g
−1
. From the bulking cases, 72% corresponded to filamentous bulking with
Thiothrix
as the most abundant filament; meanwhile, the other 28% corresponded to viscous bulking sludge in which
Zoogloea
was the most abundant genus. Furthermore, the bacterial population did not share a core of taxa across all industrial plants. However, 20 genera were present in at least 50% of the plants comprising the general core, including
Thauera
,
Ca. Competibacter
, and several undescribed microorganisms. Moreover, statistical analysis revealed that wastewater salinity strongly affected the microbial richness of the industrial plants. The bacterial population across industrial plants differed considerably from each other, resulting in unique microbial communities that are attributed to the specificity of their wastewaters.
Key points
• The general core taxa of industrial plants were mostly made up of undescribed bacterial genera.
• Filamentous bacteria constituted on average 4.1% read abundance of the industrial WWTPs.
• Viscous bulking remains a significant type of bulking within industrial WWTPs.
Journal Article
Cost minimization in a full-scale conventional wastewater treatment plant: associated costs of biological energy consumption versus sludge production
Energy consumption and sludge production minimization represent rising challenges for wastewater treatment plants (WWTPs). The goal of this study is to investigate how energy is consumed throughout the whole plant and how operating conditions affect this energy demand. A WWTP based on the activated sludge process was selected as a case study. Simulations were performed using a pre-compiled model implemented in GPS-X simulation software. Model validation was carried out by comparing experimental and modeling data of the dynamic behavior of the mixed liquor suspended solids (MLSS) concentration and nitrogen compounds concentration, energy consumption for aeration, mixing and sludge treatment and annual sludge production over a three year exercise. In this plant, the energy required for bioreactor aeration was calculated at approximately 44% of the total energy demand. A cost optimization strategy was applied by varying the MLSS concentrations (from 1 to 8 gTSS/L) while recording energy consumption, sludge production and effluent quality. An increase of MLSS led to an increase of the oxygen requirement for biomass aeration, but it also reduced total sludge production. Results permit identification of a key MLSS concentration allowing identification of the best compromise between levels of treatment required, biological energy demand and sludge production while minimizing the overall costs.
Journal Article