Multiphase CFD modeling to evaluate and to improve mixing in Chinese dome digester

Household or domestic biogas plants constitute a growing sub-sector of the anaerobic digestion industry worldwide, but had received low research attention for improvements. The Chinese dome digester (CDD), a major type of domestic biogas plant, is a naturally mixed, unheated and low tech system that is mainly used in rural areas. In this study, a multiphase computational fluid dynamics (CFD) model was applied to evaluate and subsequently improve mixing in a lab scale Chinese dome digester. The normal Chinese dome digester (CDD1) and two baffle configurations were investigated to improve the hydraulic mixing in the digester (CDD2 and CDD3 respectively) . 2-D time dependent numerical simulations were done with the three-phase, phase field model in COMSOL Multiphysics in a CDD geometry. Residence time distribution (RTD) curves were derived for all the configurations to evaluate and compare performances. In addition, three hydraulic indicators were also studied to evaluate mixing improvement. The Anaerobic digestion model No. 1 (ADM1) was used to evaluate biogas production. The effects of the addition of baffles to the CDDs did not significantly improve mixing, however about 16 % of dead zones was reduced in the two-baffle configuration

Efficiency of additives and internal physical chemical factors for pit latrine lifetime extension

Pit latrines are the most common form of on-site sanitation, but are blighted by the problem of pit fill-up. Little is known about what factors and conditions affect decomposition of pit content and thus govern pit filling, but the liquid-mass balance is the key factor. Under laboratory conditions the effect of inorganic and biological additives and the effect of physical chemical factors on solids hydrolysis of black water and human faeces were investigated to establish the potential of these to extend pit latrine lifetime. Additives did little or nothing to enhance net solids hydrolysis in batch tests or to reduce pit fill height in miniature simulated pit latrines. Physical chemical factors such as redox condition and initial pH increased solids hydrolysis, whereas temperature and substrate moisture did little. Since additives need contact with the substrate to act, measurements on faeces crust formation speed and strength were performed and showed that crusts formed within three hours and persisted after covering with fresh faeces or water

Diversity and enrichment of nitrite-dependent anaerobic methane oxidizing bacteria from wastewater sludge

Recently discovered microorganisms affiliated to the bacterial phylum NC10, named “Candidatus Methylomirabilis oxyfera”, perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO2− per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature

Closing domestic nutrient cycles using microalgae

This study demonstrates that microalgaecan effectively recover all P and N from anaerobically treated black water (toilet wastewater). Thus, enabling the removal of nutrients from the black water and the generation of a valuable algae product in one step. Screening experiments with green microalgae and cyanobacteria showed that all tested green microalgae species successfully grew on anaerobically treated black water. In a subsequent controlled experiment in flat-panel photobioreactors, Chlorella sorokiniana was able to remove 100% of the phosphorus and nitrogen from the medium. Phosphorus was depleted within 4 days while nitrogen took 12 days to reach depletion. The phosphorus and nitrogen removal rates during the initial linear growth phase were 17 and 122 mg·L−1·d−1, respectively. After this initial phase, the phosphorus was depleted. The nitrogen removal rate continued to decrease in the second phase, resulting in an overall removal rate of 80 mg·L−1·d−1. The biomass concentration at the end of the experiment was 11.5 g·L−1, with a P content of approximately 1% and a N content of 7.6%. This high algal biomass concentration, together with a relatively short P recovery time, is a promising finding for future post-treatment of black water while gaining valuable algal biomass for further application

A review of nature-based solutions for resource recovery in cities

Our modern cities are resource sinks designed on the current linear economic model which recovers very little of the original input. As the current model is not sustainable, a viable solution is to recover and reuse parts of the input. In this context, resource recovery using nature-based solutions (NBS) is gaining popularity worldwide. In this specific review, we focus on NBS as technologies that bring nature into cities and those that are derived from nature, using (micro)organisms as principal agents, provided they enable resource recovery. The findings presented in this work are based on an extensive literature review, as well as on original results of recent innovation projects across Europe. The case studies were collected by participants of the COST Action Circular City, which includes a portfolio of more than 92 projects. The present review article focuses on urban wastewater, industrial wastewater, municipal solid waste and gaseous effluents, the recoverable products (e.g., nutrients, nanoparticles, energy), as well as the implications of source-separation and circularity by design. The analysis also includes assessment of the maturity of different technologies (technology readiness level) and the barriers that need to be overcome to accelerate the transition to resilient, self-sustainable cities of the future

Biomethane from industrial and municipal wastewater

<p>Remains of drainage systems to remove waste and latrines have been found in houses from the Mesopotamian Empire (3500-2500 BC); ancient Rome had its Cloaca Maxima, and there still exists a working 4000-year-old sewer system in Greece. Nevertheless, it was not until the late nineteenth century, and after a fourteenth-century long dark age, that it was recognized that municipal waste water needs to be removed from its origin and treated to prevent the outbreak of diseases (Lofrano and Brown 2010). Until then, wastewater had been discharged in surface water or so-called “night soil” (toilet waste) and collected and used for fertilization. Later, in the early twentieth century, biological oxygen demand (BOD) was introduced as a measure of pollution and the first wastewater treatment systems were installed. Recently, the recovery of nutrients, reuse of water, production of intermediates, and generation of energy have become important incentives for the treatment of wastewater from both industrial and municipal origins. This may be more feasible through separation at the source and improved design of water usage and treatment systems (Guest et al. 2009; Larsen et al. 2009). Aerobic treatment was and still is the main technology used for the treatment of municipal wastewater in the north and cold climate areas. In the twentieth century, the possible application of anaerobic systems for the treatment of industrial wastewater and municipal wastewater in warmer climates was recognized after the development of the upflow anaerobic sludge bed (UASB) system in Wageningen in the 1970s (Lettinga 2014; van Lier et al. 2015). Nowadays, with new treatment designs and the paradigm shift toward seeing wastewater as a source of valuable resources, the application of anaerobic technology may be expanded toward treating municipal sewage in cold climates as well. Anaerobic treatment has its advantages, for example, lower excess sludge production, high applicable loadings, and lower energy demands, combined with biogas production. Initially, those were the reasons for the application of anaerobic treatment. Nowadays, the fact that nutrients (N and P) are not destroyed (e.g., emitted as N2) but released as recoverable ions is considered an additional advantage, since this facilitates recovery. Therefore, anaerobic technology has a central role in existing and newly developed waste treatment systems (Figure 3.1). It is, however, important to consider that in most cases, posttreatment of anaerobic effluent is warranted to guarantee that limits for safe discharge of the effluent are met (von Sperling and de Lemos Chrenicharo 2002).</p

Biomethane from industrial and municipal wastewater

<p>Remains of drainage systems to remove waste and latrines have been found in houses from the Mesopotamian Empire (3500-2500 BC); ancient Rome had its Cloaca Maxima, and there still exists a working 4000-year-old sewer system in Greece. Nevertheless, it was not until the late nineteenth century, and after a fourteenth-century long dark age, that it was recognized that municipal waste water needs to be removed from its origin and treated to prevent the outbreak of diseases (Lofrano and Brown 2010). Until then, wastewater had been discharged in surface water or so-called “night soil” (toilet waste) and collected and used for fertilization. Later, in the early twentieth century, biological oxygen demand (BOD) was introduced as a measure of pollution and the first wastewater treatment systems were installed. Recently, the recovery of nutrients, reuse of water, production of intermediates, and generation of energy have become important incentives for the treatment of wastewater from both industrial and municipal origins. This may be more feasible through separation at the source and improved design of water usage and treatment systems (Guest et al. 2009; Larsen et al. 2009). Aerobic treatment was and still is the main technology used for the treatment of municipal wastewater in the north and cold climate areas. In the twentieth century, the possible application of anaerobic systems for the treatment of industrial wastewater and municipal wastewater in warmer climates was recognized after the development of the upflow anaerobic sludge bed (UASB) system in Wageningen in the 1970s (Lettinga 2014; van Lier et al. 2015). Nowadays, with new treatment designs and the paradigm shift toward seeing wastewater as a source of valuable resources, the application of anaerobic technology may be expanded toward treating municipal sewage in cold climates as well. Anaerobic treatment has its advantages, for example, lower excess sludge production, high applicable loadings, and lower energy demands, combined with biogas production. Initially, those were the reasons for the application of anaerobic treatment. Nowadays, the fact that nutrients (N and P) are not destroyed (e.g., emitted as N2) but released as recoverable ions is considered an additional advantage, since this facilitates recovery. Therefore, anaerobic technology has a central role in existing and newly developed waste treatment systems (Figure 3.1). It is, however, important to consider that in most cases, posttreatment of anaerobic effluent is warranted to guarantee that limits for safe discharge of the effluent are met (von Sperling and de Lemos Chrenicharo 2002).</p

Biomethane from industrial and municipal wastewater

Remains of drainage systems to remove waste and latrines have been found in houses from the Mesopotamian Empire (3500-2500 BC); ancient Rome had its Cloaca Maxima, and there still exists a working 4000-year-old sewer system in Greece. Nevertheless, it was not until the late nineteenth century, and after a fourteenth-century long dark age, that it was recognized that municipal waste water needs to be removed from its origin and treated to prevent the outbreak of diseases (Lofrano and Brown 2010). Until then, wastewater had been discharged in surface water or so-called “night soil” (toilet waste) and collected and used for fertilization. Later, in the early twentieth century, biological oxygen demand (BOD) was introduced as a measure of pollution and the first wastewater treatment systems were installed. Recently, the recovery of nutrients, reuse of water, production of intermediates, and generation of energy have become important incentives for the treatment of wastewater from both industrial and municipal origins. This may be more feasible through separation at the source and improved design of water usage and treatment systems (Guest et al. 2009; Larsen et al. 2009). Aerobic treatment was and still is the main technology used for the treatment of municipal wastewater in the north and cold climate areas. In the twentieth century, the possible application of anaerobic systems for the treatment of industrial wastewater and municipal wastewater in warmer climates was recognized after the development of the upflow anaerobic sludge bed (UASB) system in Wageningen in the 1970s (Lettinga 2014; van Lier et al. 2015). Nowadays, with new treatment designs and the paradigm shift toward seeing wastewater as a source of valuable resources, the application of anaerobic technology may be expanded toward treating municipal sewage in cold climates as well. Anaerobic treatment has its advantages, for example, lower excess sludge production, high applicable loadings, and lower energy demands, combined with biogas production. Initially, those were the reasons for the application of anaerobic treatment. Nowadays, the fact that nutrients (N and P) are not destroyed (e.g., emitted as N2) but released as recoverable ions is considered an additional advantage, since this facilitates recovery. Therefore, anaerobic technology has a central role in existing and newly developed waste treatment systems (Figure 3.1). It is, however, important to consider that in most cases, posttreatment of anaerobic effluent is warranted to guarantee that limits for safe discharge of the effluent are met (von Sperling and de Lemos Chrenicharo 2002).</p

Biomethane from industrial and municipal wastewater

Remains of drainage systems to remove waste and latrines have been found in houses from the Mesopotamian Empire (3500-2500 BC); ancient Rome had its Cloaca Maxima, and there still exists a working 4000-year-old sewer system in Greece. Nevertheless, it was not until the late nineteenth century, and after a fourteenth-century long dark age, that it was recognized that municipal waste water needs to be removed from its origin and treated to prevent the outbreak of diseases (Lofrano and Brown 2010). Until then, wastewater had been discharged in surface water or so-called “night soil” (toilet waste) and collected and used for fertilization. Later, in the early twentieth century, biological oxygen demand (BOD) was introduced as a measure of pollution and the first wastewater treatment systems were installed. Recently, the recovery of nutrients, reuse of water, production of intermediates, and generation of energy have become important incentives for the treatment of wastewater from both industrial and municipal origins. This may be more feasible through separation at the source and improved design of water usage and treatment systems (Guest et al. 2009; Larsen et al. 2009). Aerobic treatment was and still is the main technology used for the treatment of municipal wastewater in the north and cold climate areas. In the twentieth century, the possible application of anaerobic systems for the treatment of industrial wastewater and municipal wastewater in warmer climates was recognized after the development of the upflow anaerobic sludge bed (UASB) system in Wageningen in the 1970s (Lettinga 2014; van Lier et al. 2015). Nowadays, with new treatment designs and the paradigm shift toward seeing wastewater as a source of valuable resources, the application of anaerobic technology may be expanded toward treating municipal sewage in cold climates as well. Anaerobic treatment has its advantages, for example, lower excess sludge production, high applicable loadings, and lower energy demands, combined with biogas production. Initially, those were the reasons for the application of anaerobic treatment. Nowadays, the fact that nutrients (N and P) are not destroyed (e.g., emitted as N2) but released as recoverable ions is considered an additional advantage, since this facilitates recovery. Therefore, anaerobic technology has a central role in existing and newly developed waste treatment systems (Figure 3.1). It is, however, important to consider that in most cases, posttreatment of anaerobic effluent is warranted to guarantee that limits for safe discharge of the effluent are met (von Sperling and de Lemos Chrenicharo 2002).</p

Harvest to harvest : Recovering nutrients with New Sanitation systems for reuse in Urban Agriculture

To maintain the city as a viable concept for human dwelling in the long term, a circular metabolism needs to be adopted that relies on recovering, reusing and recycling resources, in which output ('waste') from one metabolic urban conversion equals input for another. Urban Agriculture (UA) and source-separation-based New Sanitation (NS) are gaining momentum as measures for improved urban resource management. UA aims to localize food provisioning while NS aims to reorganize wastewater and organic waste management to recover valuable and crucial resources. The objective of this paper is to assess the match between the supply by NS systems and the demand from UA for nitrogen, phosphorus and organic matter, in terms of quantity and quality, to foster a circular metabolism. The research is contextualized in the city of Rotterdam. The methodology used is based on the Urban Harvest Approach (UHA), developed previously for the urban water cycle. Novel to this research is adapting the UHA to nitrogen, phosphorus and organic matter loads for two practiced UA typologies (ground-based and rooftop) and four NS concepts for the treatment of domestic urine, feces and organic kitchen waste. Results show that demand for nutrients and organic matter from UA can be minimized by 65-85% and a self-sufficiency of 100% for phosphorus can be achieved, while partial self-sufficiency for nitrogen and organic matter. This research reveals that integration of NS and UA maximizes urban self-sufficiency.</p