Low-flush Toilets Research Articles

Toilet effluent separation and brown water treatment: Survey and initial feasibility testing in Mexico

Separation of domestic effluents at the source and the utilization of low-flush toilets offer alternative approaches for developing efficient wastewater treatment systems while promoting energy generation through anaerobic digestion. This study focused on assessing toilet usage in Mexico and exploring the potential of anaerobic co-digestion of brown water (feces) and toilet paper as influential factors in wastewater treatment systems. A survey was conducted on a representative sample of Mexicans to gather information on toilet usage frequency, toilet paper use and disposal practices, as well as the type and quantity of commercial disinfectants and pharmaceutical compounds they use or consume. The survey revealed that per capita toilet paper consumption is 2.9 kg annually, that 58 % of respondents do not dispose used paper in the toilet, and that about 47 % use two to three cleaning and disinfection products. Notably, 97 % of the sampled Mexican population expressed a willingness to transition to more eco-friendly toilet options. Subsequently, in a second step, the anaerobic co-digestion of brown water with toilet paper was evaluated, demonstrating a relatively high production of volatile fatty acids but low methane production. This suggests an efficient hydrolysis/acidogenesis process coupled with restrained methanogenesis, probably due to pH decrease caused by acidogenesis. This study underscores that toilet paper and brown water are potential suitable substrates for anaerobic co-digestion. Furthermore, it sheds light on the behaviors of Mexican society regarding bathroom use and cleaning, contributing to the establishment of foundations for wastewater treatment systems with effluent separation at the source.

Promotion of low flush toilets in urban Mozambique from innovation idea to social enterprise

The Pia Fantastica toilet flushes with just one cup of water under an angle of 45 degrees and has no water seal. It has the convenience of a pedestal like a conventional ceramic toilet, and, if well installed, has no smell or fly problem. It is a toilet made out of concrete which can be produced for a price of just US$ 6.50 and is therefore attractive to the local sanitation market.The Pia Fantastica was developed as part of the Biological Urban Sanitation Project (2016–2019) where Black Soldier Fly larvae were used for environmental friendly pit emptying.The project has been translated into a social enterprise “Susamati” run by young professionals in Maputo, Mozambique. Setting up an enterprise is about building a team as well as marketing and sales. At this point, making a financially sustainable enterprise remains a challenge.

Efficient and facile integrated biological-electrocatalytic process for treating highly concentrated toilet wastewater

Low-flush toilets have received increasing attention in relation to the water crisis in water-scarce regions because the vacuum flushing system (VFS) can reduce the amount of water required for flushing by approximately 80%. However, low-flush toilet wastewater exhibits the characteristics of high pollutant concentrations and cannot be directly discharged into urban pipe networks; therefore, decentralized wastewater treatment is necessary. Traditional control process (mainly consisting of hydrolysis acidification tank (HAT), anaerobic-anoxic–oxic (AAO) tank, coagulation sedimentation filtration tank and UV disinfection) was unsatisfactory for treating this type of wastewater. Therefore, a newly designed integrated biological-electrocatalytic (AAIE) process (mainly consisting of anaerobic baffled reactor (ABR), alternating internal circulation activated sludge process (AICS), and electrocatalytic oxidation (EC)) was introduced. ABR achieved large amounts of organic matter removal, the organic biodegradation kinetics revealed that the maximum specific degradation rate of the ABR was 0.050 to 0.082 d−1; AICS further removed COD and nitrogen, the denitrification rate and growth rate of nitrifying bacteria in the AICS were in the range of 0.079–0.121 kg/(kg·d) and 0.32–1.54 d−1, respectively. The temperature and organic loading rate were identified as two key parameters for ABR and AICS to remove pollutants, therefore, EC was the guarantee to make the effluent quality met the directly discharge standard of China (GB 18918-2002), especially in winter. The results showed that the AAIE process presented COD, colority, ammonia and total nitrogen removal rates of 98.5 ± 0.7%, 98.8 ± 0.6%, 97.0 ± 0.4% and 93.4 ± 2.6%, respectively, which were considerably higher than those of the control process. Furthermore, the economic analysis indicated that the AAIE process was feasible and may help to pave the way for wide application of biological-electrocatalytic processes for highly concentrated toilet wastewater treatment.

Drainage and sewage system performance – Consequences of reductions in toilet flush volume

This study aims to evaluate impacts of reducing toilet flush volume from 6.8 to 4.8 Lpf with laboratory and field studies. In laboratory, 260 tests were performed including water consumption, waste removal and solid transport tests, in 20 different toilets produced by national and international manufacturers. These tests demonstrated that a simple reduction in flush tank water level was not a viable solution for reducing flush volume, due to flush energy loss. Toilets are designed to work with certain water volume, and reducing this volume without studying the consequences that this could cause, can make with the toilet fail. Toilets approved according the standards ABNT NBR15097, ABNT NBR15491 and ASMEA112.19.2 were installed in 10 houses. The monitoring of water consumption and sewage system videos were conducted during eight months. When 6.8-Lpf toilets were installed, the average toilet water consumption was 16.6L/inhabitant/day. For 4.8-Lpf toilets, this value increased to 17.6. The number of flushes/person/day increased after toilets replacement, indicating that users applied successive flushes. Videos showed blockages in sewage system horizontal pipes. Findings from this study suggest that low-flush toilets do not decrease total water use, and may result in increased water use. In addition, they can cause clogging and solid deposit on sewage system. Practical application: Many management failures have affected the world water availability. Water demand has increased with population growth, and unless the equilibrium between water demand and supply is restored, the world will face increasing water shortage. However, it is essential to study the way of reducing water consumption. Without an effective analysis, instead of bringing benefits to population, water consumption reduction can lead to clogging and negative consequences on sewage system performance, causing disorder to them. It is recommended that manufacturers did not reduce the toilet water consumption without a study on the impact caused on the sewage systems, as well as designers should be careful when specifying sanitary appliances.

Clogging potential of low-flush toilet branch drain system

Water scarcity is a global issue. In residential buildings, water closet appliances share the biggest portion of water consumption. Therefore, they are targeted for improvements to consume less water while keeping acceptable performance. Low-flush toilets consume a significantly smaller amount of water compared to their predecessors. However, lower water flows pose challenges like unreliable waste transportation and frequent clogging in old drainage systems. Furthermore, it is not economic to upgrade an entire drainage system to adapt to the new generation of toilets. In this study, the clogging potential for two toilet modules is investigated and the effect of hydraulic parameters on clogging is quantified. Finally, the results of this investigation are used to develop clogging potential charts for the toilets under study. Real-world application of such charts is presented.

Water Resource Management Practices of Food Establishments in Siquijor Province

Water is one of the basic needs of human beings and is imperative for sustaining the quality of life on earth (Brooks, 2006). However, its unbalanced and unmanaged use makes its scarce. Hence, this study assessed the water resource management practices of the 53 food establishments in Siquijor Province. The study utilized the descriptive survey using a self- made questionnaire which yielded that majority of the respondents are females and are in the age brackets of 18-40 and 41-62. A greater majority of the establishments were in the operation for more than ten years. As to respondents’ water resource management practices, they Often do not let water flow while cleaning or rinsing, check the water supply system for leaks and turn off unnecessary flows, and adjust water flow by the type of cleaning to be undertaken, but they Never install self-closing faucets. However, reading water meter regularly, washing only full loads in the dishwasher, and installing low flush toilets were sometimes done while installing automatic water volume controls, reusing the rinse water from the dishwasher and installing flow regulators on the faucet heads were seldom practiced. The respondents’ sex, age and number of years in operating the business had no significant relationships to their extent of water resource management practices. Thus, it is concluded that better management coupled with effective policy, awareness and efficient system is vital to enhance water resource management.

Ammonia sanitization of blackwater for safe use as fertilizer.

Source-separated blackwater from low-flush toilets contains plant-available nutrients and can be used as a fertilizer. The aim of the study was to evaluate the impact on pathogen inactivation when treating blackwater with urea and/or lime. Blackwater was spiked with Salmonella typhimurium, Escherichia coli O157, Enterococcus faecalis, and Ascaris suum eggs, and treated with urea and/or lime in concentrations up to 0.1% w/w. The bottles were kept in a storage facility (manure slurry tank) for 102 days while monitoring the pathogen concentrations. The treatment time needed to meet the requirement for Salmonella and E. coli reduction could be reduced at least six-fold. The enterococci were more persistent, and only the highest treatment doses had a significantly higher inactivation than the controls. The Ascaris egg viability was only reduced by around 50%, so higher urea/lime doses and/or longer treatment times are required to fulfill the treatment requirements of 3 log10 reductions of parasite eggs.

The Green Library Planner: What Every Librarian Needs to Know Before Starting to Build or Renovate

The librarian who is fortunate enough to be embarking on the construction of a new library space or renovation of an older library would not find a more comprehensive and thorough book than The Green Library Planner: What Every Librarian Needs to Know Before Starting to Build or Renovate, nor a more qualified author than Mary M. Carr, a librarian for forty years and a Leadership in Energy and Environmental Design (LEED)–accredited professional. Aside from websites and articles, this title is a unique reference on the topic of green building. Each of the eight chapters in this thoroughly researched book includes background information on the chapter's topic, explaining in layperson's terms the importance of the concept to be discussed. For instance, the “Energy and Lighting” chapter discusses where energy comes from, climate change, types of energy, and heat transfer before delving into how a building can be designed to have a sustainable energy system. Also included are easy-to-copy checklists to use while decisions are made during the planning and implementation processes. Each chapter concludes with a series of questions and space for project notes. The above referenced chapter asks the question: “How will the functional and the physiological needs of your employees and patrons factor into the library's energy system design?” (p. 46). The “Notes” following each chapter are comprehensive and inclusive, and the “Resources” are annotated for easy reference. The overall content of The Green Library Planner focuses on building sustainable library communities and considering economy, environment, and social equity in the process. The author begins by explaining the fundamentals of sustainable building in the first chapter and follows with a discussion of the sense of place that is distinctive to libraries whether a patron is doing research, checking email, or simply seeking a quiet space. Various types of tools are recommended throughout the book for help in decision making. Green Footstep, a carbon emissions tool developed by the Rocky Mountain Institute, is referenced in “The Importance of Place” chapter. This tool is helpful in understanding a building's potential effect on climate change and emphasizes the importance of connecting all phases of building from design to operation. Whenever necessary, the author includes definitions of terms that may be unfamiliar to librarians. The “Green Materials” chapter provides complete explanations for terms such as embodied energy, greenwashing, life cycle analysis, and pre-consumer recycled material. Also included in this chapter is an annotated and comprehensive list of directories, standards, and certifications that may be useful when researching green materials for a library construction project. Beyond discussing the library construction project itself, the author emphasizes the importance of green building design. The “Indoor Environmental Quality” chapter lists the benefits of green building to library staff and patrons as improved health and mood as well as increased productivity. In turn, the benefits to the library's bottom line include decreased absenteeism, lower turnover in staffing, and improved stakeholder relationships. Carr's expertise is evident throughout the book, making the librarian aware of the potential impact of each decision in the construction process. She points out that the level of occupancy of the library space can and does affect the air quality within the space. Water, a seemingly simple concept, is explained in detail to show the potential impact that a building can have on surrounding areas. Sustainable water solutions such as low-flush toilets and xeriscaping are discussed. The book concludes with a discussion of commissioning, a relatively new concept. Commissioning is a collaborative process that ensures that the library functions and operates as intended to be a truly green library. The Green Library Planner proves to be a valuable resource for any librarian who is an integral part of or simply desires to understand the process of building or renovating a library so that it is sustainable for the future.

The Water Short List: The Most Effective Actions U.S. Households Can Take to Curb Water Use

The long-term sustainability of many urban water supply systems in the United States is under assault from a confluence of forces. Climate change, an aging and increasingly obsolete water infrastru...

Shared Urban Greywater Recycling Systems: Water Resource Savings and Economic Investment

The water industry is becoming increasingly aware of the risks associated with urban supplies not meeting demands by 2050. Greywater (GW) recycling for non-potable uses (e.g., urinal and toilet flushing) provides an urban water management strategy to help alleviate this risk by reducing main water demands. This paper proposes an innovative cross connected system that collects GW from residential buildings and recycles it for toilet/urinal flushing in both residential and office buildings. The capital cost (CAPEX), operational cost (OPEX) and water saving potential are calculated for individual and shared residential and office buildings in an urban mixed-use regeneration area in the UK, assuming two different treatment processes; a membrane bioreactor (MBR) and a vertical flow constructed wetland (VFCW). The Net Present Value (NPV) method was used to compare the financial performance of each considered scenario, from where it was found that a shared GW recycling system (MBR) was the most economically viable option. The sensitivity of this financial model was assessed, considering four parameters (i.e., water supply and sewerage charges, discount rate(s), service life and improved technological efficiency, e.g., low flush toilets, low shower heads, etc.), from where it was found that shared GW systems performed best in the long-term.

Modelling the effects of on-site greywater reuse and low flush toilets on municipal sewer systems

On-site greywater reuse (GWR) and installation of water-efficient toilets (WET) reduce urban freshwater demand. Research on GWR and WET has generally overlooked the effects that GWR may have on municipal sewer systems. This paper discusses and quantifies these effects. The effects of GWR and WET, positive and negative, were studied by modelling a representative urban sewer system. GWR scenarios were modelled and analysed using the SIMBA simulation system. The results show that, as expected, the flow, velocity and proportional depth decrease as GWR increases. Nevertheless, the reduction is not evenly distributed throughout the day but mainly occurs during the morning and evening peaks. Examination of the effects of reduced toilet flush volumes revealed that in some of the GWR scenarios flows, velocities and proportional depths in the sewer were reduced, while in other GWR scenarios discharge volumes, velocities and proportional depths did not change. Further, it is indicated that as a result of GWR and installation of WET, sewer blockage rates are not expected to increase significantly. The results support the option to construct new sewer systems with smaller pipe diameters. The analysis shows that as the penetration of GWR systems increase, and with the installation of WET, concentrations of pollutants also increase. In GWR scenarios (when toilet flush volume is not reduced) the increase in pollutant concentrations is lower than the proportional reduction of sewage flow. Moreover, the results show that the spatial distribution of houses reusing GW does not significantly affect the parameters examined.

A review of wastewater handling in the Arctic with special reference to pharmaceuticals and personal care products (PPCPs) and microbial pollution

Treatment of wastewater is often inadequate or completely lacking in Arctic regions. Wastewater contains different kinds of substances that can be harmful for the environment and human health, including residues of pharmaceuticals and personal care products. Bioaccumulation and biomagnifications of chemicals in the food web are of concern. This can affect fishery that is a significant industry in many Arctic coastal regions. Wastewater from human settlements may also contain antibiotic resistant bacteria and pathogens that can cause negative impacts on human health and the environment. In the Arctic, especially, the direct release of untreated sewage may have severe consequences for the receiving environment due to low biological diversity, low ambient temperatures and consequently high vulnerability of the Arctic ecosystem to environmental contaminants.Bucket toilets are common in remote settlements but are also used in towns. In settlements having inadequate sanitary facilities the risk of contracting diseases, such as hepatitis A, is unacceptably high. Conventional centralized wastewater collection systems and treatment plants are a challenge to build in the Arctic and expensive to operate. Thus alternative methods are needed. Possible solutions are improved dry or low flush toilets with collection of toilet waste at the household level and subsequent centralized treatment by dry composting or anaerobic digestion. Both treatment methods facilitate co-treatment of wastewater along with other organic waste fractions and provide a by-product that is environmentally safe and easy to handle. Combining the above with decentralized greywater treatment will reduce the costs for expensive infrastructure.

Bad for the environment, good for the farmer? Urban sanitation and nutrient flows

Due to poor urban sanitation farmers in and around most cities in developing countries face highly polluted surface water. While the sanitation challenge has obvious implications for environmental pollution and food safety it can also provide ‘free’ nutrients for irrigating farmers. To understand the related dimensions, a box-flow model was used to identify the most important water and nutrient flows for the Ghanaian city of Kumasi, a rapidly growing African city with significant irrigation in its direct vicinity. The analysis focused on nitrogen and phosphorus and was supplemented by a farm based nutrient balance assessment. Results show that the city constitutes a vast nutrient sink that releases considerable nutrients loads in its passing streams, contributing to the eutrophication of downstream waters. However, farmers have for various practical reasons little means and motivation in using this resource of nutrients. This might change under increasing fertilizer prices as the nutrient load will continue to increase by 40% till 2015 assuming a widening gap between population growth and investments in water supply on one side and investments in sanitation on the other. However, even a strong investment into flushing toilets would not reduce environmental pollution due to the dominance of on-site sanitation systems, but instead strongly increase water competition. Key options to reduce the nutrient load would be via optimized waste collection and investment in dry or low-flush toilets. The latter seems also appropriate for the city to meet the water and sanitation Millennium Development Goals (MDGs) without increasing water shortages in toilet connected households.

“New” Water

We are continually inundated with news and views about the demand for water outpacing supply. Our unsustainable development along rivers that do not reach the sea, declining ground water levels, damage to wetlands, high costs associated with acquiring new sources of water, and potential shortages related to global climate change are common news items. In most developed economies, there is little or no unallocated fresh water left to exploit. So, the question becomes: Where do we find “new” water for our burgeoning population? The answer may lie in the treatment of both shallow, brackish ground water and postconsumer water. Recent advances in reverse-osmosis membranes have reduced operational costs and established a linear correlation between total dissolved solids and operational cost of desalination; thus, there is increased interest in brackish water as input source. In the Southwest, the El Paso, Texas, Water Utilities Public Service Board recently dedicated a 100 million L/d desalination plant. Surprisingly, Florida with its high rainfall of more than 100 cm a year and many lakes and rivers is commonly thought of as a water-“rich” state; yet it has more water desalination plants than any other state: the city of Tampa Bay has the largest active desalination plant in the United States and uses brackish water from Tampa Bay. It is estimated that the state of New Mexico contains 16,000 billion m3 (13 billion acre-feet) of shallow brackish ground water (total dissolved solids greater than 500 mg/L and less than sea water, which is 35,000 mg/L). I suspect that development of brackish water aquifers would, in general, have less impact on the ecology than development of fresh water aquifers. That being said, we know little about the extent and chemistry of brackish water aquifers and almost nothing about their boundary conditions. Thus, I propose a federal 10-year sunset assessment of 1‰ per 250 gallons on all the ground water that municipalities extract, or about $1.00 each year for the average household using ground water. It is envisioned that this study would quantify the regional hydrology of these aquifers following the USGS’s Regional Aquifer System-Analysis model for fresh water aquifers. It would also identify any potential deeper formations capable of sequestering desalination concentrate. This small investment coupled with reduced consumption from increased rate changes and conservation measures such as low-flush toilets, low-flow showerheads and watering restrictions will prolong our existing resources and give us time to install the necessary infrastructure. We need to wean ourselves from our “once through, throw it out” philosophy that dominates current water resource management. We also need to reframe the linguistic argument away from “sewerage” or “waste water” toward the more societally acceptable “postconsumer” or “surplus municipal water.” (Remember, it is not a “used” car, it is a “previously owned” car!) Cities will soon no longer have the luxury of passing their used municipal water downstream. “Dilution is the solution to pollution” is a dated and unfair concept of passing water quality problems to the aquatic environment and cleanup expenditures to downstream users. Newly engineered membranes in desalination plants are excellent at removing not only salts but also pharmaceuticals, endocrine disruptors, prions, and other undesirable products left untouched by conventional waste treatment facilities. Combining membrane-treated water with aquifer storage and recovery (ASR) offers some interesting water management possibilities. That is, by recharging refreshed water, which is generally of better quality than native ground water, into aquifers, one can control the blending ratio of refreshed to native ground water in producing well fields. Furthermore, the aquifer provides a unique environment to adjust the temperature and chemistry and continue filtering the recharged water, adding insurance against the transport of many undesirable contaminants. Desalination and ASR are, however, energy-intensive processes; thus, greenhouse gas–free energy is likely to be integrated in any future energy scenario. Currently, approximately 28% of all electrical power generated in the United States is greenhouse gas–free (nuclear 19.3%, hydro 6.5%, biofuels 1.6%, wind less than 1%, and solar less than 1%), so these are likely to be the energy sources for desalination. Because both the membrane and the ASR technologies are mature and well established, development of new water from brackish ground water and postconsumer water could be a rapid and straightforward resolution to many of the domestic and industrial demands of our nation’s water resources well into the future.

Wastewater management integrated with farming –an environmental systems analysis of a Swedish country town

Recycling of plant nutrients in sewage products to arable land is considered to be a step towards a more sustainable society. Sewage sludge is the predominant sewage fertiliser product available today, but the use of sewage sludge in agriculture has been questioned as regards hazardous substances. In this respect, blackwater from separating systems seems to better fulfil agricultural requirements regarding fertiliser products. The objective of this paper was to analyse the environmental impact and resource use in a life cycle perspective for three systems, each including both wastewater handling and agricultural production. In the reference system, food waste disposers were installed in houses. Milled food waste and wastewater were treated in a wastewater treatment plant and the sewage sludge was used for producing a soil conditioner. In the sludge utilisation system, food waste from households was composted, wastewater was treated conventionally and sewage sludge was used in oat production. In the blackwater system, toilet water from low-flush toilets and milled organic waste were digested together and spread in growing oats. Data on the wastewater system were derived from simulations by the substance-flow model URWARE/ORWARE. The blackwater system required slightly more primary energy than the other two systems. In particular, construction of storage facilities contributed considerably to energy use. The emissions of greenhouse gases and SO 2 were of the same magnitude for all three systems, while the eutrophying emissions were reduced significantly in the blackwater system. As regards NH 3 and NO X , the emissions were highest for the blackwater system. High substitution of mineral fertiliser, optimal spreading technique and well-designed collection and storage facilities were important factors for the environmental outcome in the blackwater system.

MODELLING THE IMPACTS OF DOMESTIC WATER CONSERVATION ON THE SUSTAIN ABILITY OF THE URBAN SEWERAGE SYSTEM

A computer model was developed to evaluate the impact of various technologies for water conservation in domestic households, in terms of the impact on the operation of downstream infrastructure. These technologies, which include (a) low-flush toilets, (b) greywater re-use, and (c) re-use of rainwater from roof runoff for toilet flushing, were compared using indicators of sustainability to measure water consumption, sewerage-system operational performance and process treatment efficiency. The results demonstrated that rainwater re-use is potentially the most sustainable strategy in terms of the benefits associated with water conservation and reduction in sewage discharges from combined-sewer overflows (CSOs). The benefits were observed without the problems associated with increased sedimentation in sewers during dry weather, associated with other water-conservation strategies such as reduced-flush toilets, greywater re-use and the resultant increase in pollutants from CSOs during wet weather.