Ultrafine bubbles as an augmenting agent for ozone-based advanced oxidation.

In this study, the influence of nanobubbles (NBs) application in ozone (O3) based advanced oxidation processes (AOP) is investigated. The results demonstrate the potential of NBs application to O3 - based AOP. It was observed that NBs suppress the negative influence of pH and operating temperatures on the efficiency of ozonation. In addition, the application of NBs tends to improve the solubility of O3 and the rate of mass transfer under the influence of a broad range of temperature and pH conditions. The results of this research indicate that application of NBs minimized the reduction in concentration of dissolved O3 with an increase in temperature. Furthermore, application of NBs highly improved the OH radical formation in acidic conditions. The results of this research depicted for first time that the application of NBs strongly encourages the initiation of reactions involving OH radicals. It was found by this research that NBs can boost the concentration of OH radicals up to 3.5 fold compared to equivalent MB-supported ozonation systems. This is assumed to improve the efficiency of currently existing conventional bubble supported O3 - based AOP systems.

The effect of number of tanks on water quality in rainwater harvesting systems under sudden contaminant input.

Rainwater harvesting (RWH) is a sustainable solution for curbing existing urban water crises. Many countries have implemented various design guidelines for RWH systems, but water quality issues persist, especially with respect to particulate matter and soluble contaminants entering the RWH system after a prolonged dry period. A first-flush unit in an RWH system can partially manage this sudden influx of pollutants, provided that rainfall conditions are favorable for its optimal operation. Therefore, a significant proportion of these pollutants reach the storage tank. The most common single storage tank RWH systems accumulate particulate matter, and allow soluble and particulate contaminants to reach the outlet quickly at undesirably high concentrations. To overcome these issues pertaining to single tank systems, multiple tank systems with similar volumes have been implemented globally. However, limited research has been conducted to assess the effect of the number of tanks on harvested water quality under a sudden pollutant input. Hence, the authors have investigated the effect of the number of tanks on particulate matter distribution in multi-tank systems, and observed that more than 60% of the particle mass input was retained in the first tank. By increasing the number of tanks, the particle mass reaching the final tank becomes constant despite changes in the flowrate and influx particle mass. Furthermore, a soluble contaminant entering a multi-tank system was observed to reside within the system for a prolonged time by approximately a factor of two, which is favorable for developing a response strategy. It is recommended by the authors that at least three tanks should be used to gain the benefits of a multiple-tank RWH system.

On-site rainwater harvesting and treatment for drinking water supply: assessment of cost and technical issues.

This study assessed the performance of rainwater-harvesting systems installed for selected public utilities in the northern provinces of Vietnam where rainwater was collected, stored in stainless steel tanks, and treated with a complex filtration unit and Ultraviolet (UV) disinfection system (full system). Results from an operation of over 5 years show that the untreated rainwater could not be used directly for drinking purposes as it was contaminated with bacteria (total coliforms TC = 200-300 CFU/100 ml, Pseudomonas aeruginosa PA = 40-160 CFU/100 ml), and turbidity = 2-4 NTU. Most of the heavy metals detected were found below the standard limits. Phenol and its derivatives were detected occasionally as higher than the standard value (1 µg/L). After treatment, all parameters met the drinking water standards. The capital costs of the rainwater systems were approximately US$200/m3 and US$180/m3 for a full system and simplified system (without complex filtration unit), respectively, while the operation and maintenance (O&M) costs were 3 cents/L and 0.8 cents/L on average for a full system and simplified one, correspondingly.

Evaluation of different natural additives effects on the composting process of source separated feces in resource-oriented sanitation systems.

In most resource-oriented sanitation (ROS) systems, the composting process has been a sustainable treatment method for source separated feces. Nonetheless, a slow and low degradation efficiency-combined with hygienic concerns, especially for the high amount of waste produced -makes the selection of the composting bulk additives a critical decision for the process. This study presents the efficiency improvement of adding different natural additives to enhance the composting process of the source separated feces in ROS systems. Three different natural additives, including sawdust, rice husk, and rice husk charcoal were utilized for the composting process of fresh feces with an additive w/w ratio of 2:1. To evaluate the impact of additives on compost properties, chemical, physical, and biological characteristics of composting materials were measured. Results indicated that using rice husk charcoal as an additive of the process was effective and generated a degradation of more than 40% of total organic carbon (TOC), reduced the nitrogen loss to less than 0.2%, and improved the germination index (GI) to more than 80%. Moreover, in terms of fecal indicators, the Escherichia coli (E. coli) stains were totally removed after five weeks. The efficacy of utilizing rice husk charcoal as a composting matrix in resource oriented sanitation systems can be, therefore, demonstrated as a nature-based treatment for source separated feces.

A new approach for modeling flux variation in membrane filtration and experimental verification.

It is important to model flux variation during the membrane filtration process, particularly in the early stage of filtration where severe fouling causes rapid flux decay in a short period of time. The objective of this study was to develop a combined fouling mathematical model based on energy head loss principle for prediction of flux variation in the membrane filtration. The complete-cake model was employed in the model in order to describe the loss of membrane available area due to pore clogging, while, the classical cake model was used for cake filtration. A new dimensionless parameter, namely the filter number (FN) was proposed in this study to account for the unmeasurable properties of the membrane in the model. The application of the proposed model was tested and compared with the existing models using experimental data for the filtration of wastewater sludge, microalgae suspension and sodium alginate solution with different membranes and pressures. The results showed that the flux calculated values of the new model had good agreements with the experimental data under different conditions. According to statistical analyses, the model improved the representing accuracy of flux variation in the early stage of filtration. In addition, the model provides better performance and efficiency in comparison to the existing models for high flux operations which is more conventionally applied in the industry and is expected to be more in the future.

Field evaluation of the fertilizing potential of biologically treated sanitation products.

Among different approaches of treating source-separated urine and feces for agronomic utilization, the treatment by addition of nitrifying bio-seeds seems to be useful in increasing the fertilizing potential of these sanitation products by modifying and stabilizing the nitrogen profile. In this study, biological treatment was applied to an onsite resource-oriented sanitation system by adding nitrifying microorganism bio-seeds. Further, the potential of the sanitation products to be utilized as fertilizer for white radish (Raphanus sativus var. longipinnatus) cultivation was examined and compared with that of a commercial fertilizer. This was done through the measurement of nutrients released in soil samples as well as measurements of root mass, root length, and the measurement of accumulated nitrogen, sugar, and water content in plant tissues. Our results show that soil fertilized with a mixture of biologically treated urine and feces exhibits a statistically similar nutrient release trend to soil fertilized using a commercial fertilizer. Moreover, soil fertilized with a mixture of biologically treated urine and feces yielded larger white radishes with a higher sugar and water content, as well as a higher accumulation of nutrients in the plant tissues, than soil fertilized with a commercial fertilizer.

The effects of surfactants (sodium dodecyl sulfate, triton X-100 and cetyl trimethyl ammonium bromide) on the dewaterability of microalgae biomass using pressure filtration.

The application of pressure filtration in microalgae harvesting requires chemical pretreatment in order to reduce membrane fouling and to increase water flux. Surfactants have shown potential to enhance microalgae dewaterability by charge neutralization, bridging and releasing extracellular polymeric substances (EPS) and bound water. In this study, the effect of three surfactants including anionic sodium dodecyl sulfate (SDS), non-ionic triton X-100 and cationic cetyl trimethyl ammonium bromide (CTAB) on the dewaterability of Chlamydomonas sp. was investigated. Filtration fluxes and biomass concentrations were used to evaluate the microalgae dewaterability. Based on the results, SDS and Triton X-100 had a negative effect on the dewaterability of microalgae biomass. However, CTAB improved the dewaterability by decreasing the reversible and irreversible fouling resistance. The optimum dosage of CTAB was found to be 1500 mg/L, and resulted in 95.8% and 140% improvement on average water flux and biomass recovery efficiency, respectively.

Design parameter estimations for adjustable bubble size in bubble generating system.

In this study, we developed a customized low cost and low energy bubble generator that can control bubble size. Hence, it can be used not only in the water treatment process but also in various other processes. This device was able to generate bubbles with a very simple system using only a general pump and a mixing chamber. Increasing the number of partition walls in the mixing chamber reduced the bubble size. Furthermore, bubbles of a few hundred nanometers were produced by the shear stress caused by increasing the thickness of the partition wall. Although the generated sub-micron bubbles were too small for their exact size to be measured using an image analysis and particle counting method, it was possible to confirm their existence indirectly through the coalescence arising from ultrasonic irradiation. The device used in this research is simple and allows bubble size to be adjusted easily by controlling the design of the mixing chamber. Therefore, it can be applied to a water treatment process, as well as a variety of other processes.

Fate of Fecal Indicators in Resource-Oriented Sanitation Systems Using Nitrifying Bio-Treatment.

Hygienic fecal treatment in resource-oriented sanitation (ROS) systems is an important concern. Although the addition of nitrifying microorganisms is a sustainable fecal treatment method in ROS systems, it is essential to examine the cleanliness of this method. In this study, we investigated the fate of fecal indicators in source-separated fecal samples through tracking Escherichia coli and total coliforms. The effects of adding different amounts of Nitrosomonas europaea bio-seed, along with a constant amount of Nitrobacter winogradskyi bio-seed, were studied. In intact feces samples, the pathogen population underwent an initial increase, followed by a slight decrease, and eventually became constant. Although the addition of nitrifying microorganisms initially enhanced the pathogen growth rate, it caused the reduction process to become more efficient in the long-term. In addition to a constant concentration of 10,000 cells of N. winogradskyi per 1 g feces, a minimum amount of 3000 and 7000 cells of N. europaea per 1 g feces could completely remove E. coli and total coliforms, respectively, in less than 25 days. Increasing the amount of bio-seeds added can further reduce the time required for total pathogen removal.

Harvesting nutrients from source-separated urine using powdered rice straw.

As a principle of resource-oriented sanitation practice, urine should be separated from the source and utilized for other purposes such as producing fertilizer. This is because urine is rich in nutrients; therefore, sending it directly to wastewater treatment plants causes problems in the regular treatment process. The addition of solid additives such as powdered rice straw can help with harvesting nutrients from urine. In this study, the procedure and efficiency of using powdered rice straw for nutrient harvesting were investigated by tracking the reductions in ammonia, phosphate, magnesium, and calcium ions, and the harvested nutrients were identified using crystallography methods. Results show that the ammonia, phosphate, and magnesium ions showed similar reduction trends. However, the reduction process was limited by the magnesium and phosphate availability, which reduced the nutrient harvesting efficiency. The nutrients harvested with the rice straw were identified to be mostly struvite. Balancing the phosphate and magnesium ions with ammonia is recommended to improve the efficiency of nutrient harvesting. The treated powdered rice straw can serve as a good solid fertilizer, while the remaining urine, which includes fewer nutrients, can be utilized for irrigation or sent to wastewater treatment plants.

Optimizing source-separated feces degradation and fertility using nitrifying microorganisms.

Resource-oriented sanitation (ROS) systems play an important role in handling source-separated human sanitary wastes intended to be used for other purposes. Usually, the purpose of employing such systems is to render the source-separated human feces suitable as fertilizer or soil conditioner. However, the high volume, low degradation rate, and lack of fertility management pose challenges to such enterprises. Accordingly, treatment by applying controlled amounts of nitrifying microorganisms could be useful. The effect of adding different amounts of Nitrosomonas Europaea bio-seed, along with a certain amount of Nitrobacter Winogradskyi bio-seed, to source-separated human feces was investigated. The results show that adding 7000-8000 or more N. Europaea cells, along with 10,000 N. Winogradskyi cells, to 1 g feces, resulted in up to 90% degradation of the organic matter by enhancing the growth of heterotrophic microorganisms. Moreover, the nitrogen composition and pH of the degraded feces were optimized to meet the criteria for standard fertilizer. The results can be useful for managing source-separated feces in ROS systems in accordance with the specific aims of such systems, i.e., reducing feces volume by bio-degradation and increasing the fertility to meet the standard criteria for fertilizer.

Micro and nanobubble technologies as a new horizon for water-treatment techniques: A review.

This review article organizes the studies conducted on the areas of microbubbles and nanobubbles with a special emphasis on water treatment. The basic definitions of bubble types and their size ranges are also presented based on the explanations of different researchers. The characterization parameters with state-of-the-art measuring and analysis techniques of microbubble and nanobubble technologies are summarized. Some major applications of these technologies in water-treatment processes are reviewed and briefly discussed. Based on the reviews, various potential areas for research and bubble application gaps in water and wastewater treatment technologies are identified for further study. The article is prepared in such a way that it provides a step-by-step acquaintance to the subject matter with the objective of focusing on the application of microbubbles and nanobubbles in water-treatment technology.

Consideration of rainwater quality parameters for drinking purposes: A case study in rural Vietnam.

Rainwater, which is used for drinking purposes near Hanoi, Vietnam, was analysed for water quality based on 1.5 years of monitoring data. In total, 23 samples were collected from different points within two rainwater harvesting systems (RWHSs). Most parameters met the standard except micro-organisms. Coliform and Escherichia coli (E. coli) were detected when the rainwater was not treated with ultraviolet (UV) light; however, analysis of rainwater after UV sterilisation showed no trace of micro-organisms. The RWHSs appear to provide drinking water of relatively good quality compared with surface water and groundwater. The superior quality of the rainwater suggests the necessity for new drinking rainwater standards because applying all of the drinking water quality standards to rainwater is highly inefficient. The traditionally implemented standards could cause more difficulties for developing countries using RWHSs installed decentralized as a source of drinking water, particularly in areas not well supplied with testing equipment, because such countries must bear the expense and time for these measures. This paper proposes the necessity of rainwater quality guideline, which could serve as a safe and cost-effective alternative to provide an access to safe drinking water.

Urban rainwater harvesting systems: Research, implementation and future perspectives.

While the practice of rainwater harvesting (RWH) can be traced back millennia, the degree of its modern implementation varies greatly across the world, often with systems that do not maximize potential benefits. With a global focus, the pertinent practical, theoretical and social aspects of RWH are reviewed in order to ascertain the state of the art. Avenues for future research are also identified. A major finding is that the degree of RWH systems implementation and the technology selection are strongly influenced by economic constraints and local regulations. Moreover, despite design protocols having been set up in many countries, recommendations are still often organized only with the objective of conserving water without considering other potential benefits associated with the multiple-purpose nature of RWH. It is suggested that future work on RWH addresses three priority challenges. Firstly, more empirical data on system operation is needed to allow improved modelling by taking into account multiple objectives of RWH systems. Secondly, maintenance aspects and how they may impact the quality of collected rainwater should be explored in the future as a way to increase confidence on rainwater use. Finally, research should be devoted to the understanding of how institutional and socio-political support can be best targeted to improve system efficacy and community acceptance.

Optimization of fertilization characteristics of urine by addition of Nitrosomonas europaea bio-seed.

BACKGROUND: Because of the high concentration of nutrients in human urine, its utilization as an organic fertilizer has been notable throughout history. However, the nitrogen compounds in urine are not stable. Therefore, to convert urine into a suitable fertilizer, it is important to stabilize and adjust unstable nitrogen compounds such as ammonia. Because nitrification can influence the nitrogen profile, the use of nitrifying microorganisms can be useful for stabilizing the nitrogen profile of urine. This study investigated the changes in nitrogen compounds in pure urine and examined the effect of adding Nitrosomonas europaea bio-seed solution on these changes. RESULTS: It was found that the addition of bio-seed could reduce nitrogen loss as well as the time required to stabilize the nitrogen profile. Furthermore, the optimum concentration of bio-seed (6 × 10(5) N. europaea cells L(-1) ) that not only leads to the least nutrient loss but also results in an adequate nitrate/ammonium ratio and regulates the amount of nitrate produced, thereby preventing over-fertilization, was determined. CONCLUSION: At this concentration, no dilution or dewatering is required, thus minimizing water and energy consumption. Usage of the optimum of concentration of bio-seed will also eliminate the need for inorganic chemical additives. © 2016 Society of Chemical Industry.

The Waterless Portable Private Toilet: An Innovative Sanitation Solution in Disaster Zones.

Catastrophes can occur without warning and inevitably cause short-term and long-term problems. In disaster zones, having an action plan to alleviate difficulties can reduce or prevent many long-lasting complications. One of the most critical and urgent issues is sanitation. Water, energy, personnel, transportation, and the allocation of resources in disaster areas tend to become very limited during emergencies. Sanitation systems suffer in the process, potentially leading to crises due to unsafe and unhygienic surroundings. This article explores the problems of current sanitation practices in disaster areas and identifies the essential characteristics of sustainable sanitation systems. This study also presents a plan for an innovative and sustainable sanitation system using a waterless, portable, private toilet, in addition to a procedure for collecting and disposing waste. The system is agronomic, is socially acceptable, prevents contact with human waste, and can be used for individuals or families. Environmental pollution and social problems (such as sexual harassment) can be reduced both during and after restoration.

The effect of material and flushing water type on urine scale formation.

One of the important challenges with current sanitation practices is pipe blockage in urinals caused by urine scale formation. Urinal material and flushing water type are the two most important factors affecting scale formation. This paper examines the scale formation process on different materials which are commonly used in urinal manufacturing and exposed to different urine-based aqua cultures. This study shows that urine scale formation is the greatest for carbon steel material, and the least for PVC. Additionally, material exposure to the urine-rainwater mixture resulted in the smallest amount of scale formation. Based on these results, two new methods for improving sanitation practices are proposed: (1) using PVC as production material for urinals and pipelines; and (2) using rainwater for flushing systems.

A pilot study to evaluate runoff quantity from green roofs.

The use of green roofs is gaining increased recognition in many countries as a solution that can be used to improve environmental quality and reduce runoff quantity. To achieve these goals, pilot-scale green roof assemblies have been constructed and operated in an urban setting. From a stormwater management perspective, green roofs are 42.8-60.8% effective in reducing runoff for 200 mm soil depth and 13.8-34.4% effective in reducing runoff for 150 mm soil depth. By using Spearman rank correlation analysis, high rainfall intensity was shown to have a negative relationship with delayed occurrence time, demonstrating that the soil media in green roofs do not efficiently retain rainwater. Increasing the number of antecedent dry days can help to improve water retention capacity and delay occurrence time. From the viewpoint of runoff water quality, green roofs are regarded as the best management practice by filtration and adsorption through growth media (soil).

Solar disinfection of Pseudomonas aeruginosa in harvested rainwater: a step towards potability of rainwater.

Efficiency of solar based disinfection of Pseudomonas aeruginosa (P. aeruginosa) in rooftop harvested rainwater was evaluated aiming the potability of rainwater. The rainwater samples were exposed to direct sunlight for about 8-9 hours and the effects of water temperature (°C), sunlight irradiance (W/m2), different rear surfaces of polyethylene terephthalate bottles, variable microbial concentrations, pH and turbidity were observed on P. aeruginosa inactivation at different weathers. In simple solar disinfection (SODIS), the complete inactivation of P. aeruginosa was obtained only under sunny weather conditions (>50°C and >700 W/m2) with absorptive rear surface. Solar collector disinfection (SOCODIS) system, used to improve the efficiency of simple SODIS under mild and weak weather, completely inactivated the P. aeruginosa by enhancing the disinfection efficiency of about 20% only at mild weather. Both SODIS and SOCODIS systems, however, were found inefficient at weak weather. Different initial concentrations of P. aeruginosa and/or Escherichia coli had little effects on the disinfection efficiency except for the SODIS with highest initial concentrations. The inactivation of P. aeruginosa increased by about 10-15% by lowering the initial pH values from 10 to 3. A high initial turbidity, adjusted by adding kaolin, adversely affected the efficiency of both systems and a decrease, about 15-25%; in inactivation of P. aeruginosa was observed. The kinetics of this study was investigated by Geeraerd Model for highlighting the best disinfection system based on reaction rate constant. The unique detailed investigation of P. aeruginosa disinfection with sunlight based disinfection systems under different weather conditions and variable parameters will help researchers to understand and further improve the newly invented SOCODIS system.