Disinfection by The Portable Natural Biological System – a completely Nature – Based sustainable solution for clean water supply

Abstract: The portable Natural Biological System™ (P-NBS), developed in Israel by Ayala Water & Ecology, is a cost-effective, easy-to-install, stable, energy-free, nature-based solution to purify contaminated water. The PNBS solves freshwater scarcity in rural and remote areas; provides alternatives for sustainable urban development while rapidly providing quality water, meeting strict regulatory demands. The PNBS can be immediately supplied to any location based on shipping container dimensions. Results show that the NBS consistently removes 3-5 log10 Fecal Coliforms (MPN/100 mL) beginning with raw sewage, sufficient for unrestricted irrigation according to World Health Organization guidelines. To comply with drinking water regulations for the purification of contaminated source water, the NBS must be combined with a solid-state disinfectant that compares to chlorine in effectiveness, safety, and residual disinfectant. Since chlorine needs to be constantly replenished and dosed according to flow rate, it may be untenable for application in a remote village. Hence the current research proposal aims at tailoring various disinfection agents, such as nano- silver/copper, quaternary cations, doped Granulated Activated Charcoal, and Expanded Clay Aggregate, for use in the PNBS to provide drinking water in underserved rural areas with maximal efficacy and safety, minimal maintenance, replacement, and energy needs.

The Portable NBS

Background: 80% of all people without access to safe drinking water worldwide live in rural and remote areas. In 2015, 2.1 billion people lived without safely managed drinking water services, including:

  • 3 billion people with essential services, a clean water source located within a round trip of 30 minutes
  • 263 million people with limited services or a clean water source requiring more than 30 minutes to collect water
  • 423 million people taking water from unprotected wells and springs
  • 159 million people collect untreated surface water from lakes, ponds, rivers, and streams.


Lack of clean water seriously affects health; 1.8 million children under five die yearly from a water-related disease every 20 seconds. Over half of the world’s hospital beds are occupied by people suffering from illnesses due to contaminated water. More people die due to polluted water than are killed by all forms of violence, including wars. The pollution can be attributed to inadequate infrastructure and management systems for wastewater and, consequently, to contaminated drinking water. Ninety percent of sewage in developing countries is discharged untreated directly into rivers, lakes, or the oceans, contaminating freshwater sources and polluting the seas. This pollution reaches the drinking water supplies that are often consumed without treatment.

In recent years, increased connectivity to social networks coupled with political unrest has led to unprecedented amounts of political refugees and migrants seeking a stable life. Migration challenges achieving the availability and sustainable management of water and sanitation for all globally (UN, 2017). Migrants face significant barriers to accessing WASH services, especially in transit and informal areas. Service providers face numerous technical and financial challenges in meeting the needs of migrants, as the provision of safely-managed services requires significant capital investment and is usually designed to be delivered to a household. These challenges are compounded by large and abrupt flows of migrants and refugees, and where migrants are living in informal, unincorporated, or temporary accommodations. This tragic situation is visible throughout the Middle East and Europe as a consequence of Syria’s long civil war and Africa due to the Sub-Saharan states’ economic conditions. The effect has become a significant challenge in Europe with the influx of refugees over the last few years and is significantly impacting the political climate. Hence the need to supply clean water is also a strategically important issue with implications for health, the environment, and society.

While it may seem that the issue of clean drinking water is a problem in the developing world, even in Europe, 60% of the rural population lacks adequate access to water services1. In Europe, 1 in 10 citizens obtains their drinking water from small-scale systems. Small-scale system water sources are very vulnerable to contamination. In many rural settings, groundwater is used for drinking without disinfection, regardless of its contamination level2. In the Mediterranean Basin, a substantial proportion of wastewater is discharged into the sea untreated. In this area, 5110 diarrhea deaths per year are attributable to inadequate water sanitation, a severe threat to public health, notwithstanding the environmental impact and the negative economic impact on the sustainability of these areas. This lack of water security can cause unstable political scenarios and continues pushing immigration to the cities.

The main reason for inequality in water sanitation services is low economic capacity, low population density, and inaccessible orography of these regions. The main driver of investments in water treatment is efficiency relative to the Population covered; therefore, small communities lack the necessary resources to build water treatment facilities and provide adequate operation and maintenance to existing facilities and networks.

It is essential to provide a reliable, onsite water purification system capable of treating any nearby contaminated water source to the appropriate hygienic quality for human consumption. In addition, the system needs to function independently, with minimal human intervention (workforce, chemicals, energy), and have minimal infrastructural needs to apply to remote or inaccessible places where it is most needed. Finally, the solution should not only supply clean water from a polluted source but also manage wastewater and protect clean sources from future contamination. The portable Natural Biological System (PNBS) answers all these demands.

 Microbial Pathogens: 

When referring to microorganism concentration and removal in contaminated water, it is helpful to use a logarithmic scale since huge numbers and ranges can be encountered (Bitton, 2011). The removal efficiency for various pathogens differs by orders of magnitude and is affected by Physico-chemical parameters such as the type of cells’ envelope (cyst, protein coat, lipid), the density of the particle (e.g., most helminth eggs are removed by gravity during primary clarification) and subtle biochemical effects involving DNA integrity and repair under stress conditions (USEPA/USAID, 2012). For the sake of illustration, typical removal rates of the fecal indicator, Escherichia coli, by secondary treatment and chlorination (a common combination for agricultural reclamation) is up to 6-log units, while for the fecal protozoa Cryptosporidium parvum and Giardia lamblia, the removal is only up to 3-log units (USEPA/USAID, 2012).

Pathogens in wastewater (WW) include members of various taxa within the bacteria, virus, protozoa, and helminth groups. Many of the pathogens that can be found in WW are characterized by high initial concentrations and low minimal


World Health Organization. (2010). Small-scale water supplies in the pan-European region. Geneva: The Regional Office for Europe of the World Health 2 Organization.

An infectious dose (MID) is the number of cells or particles that cause illness in approximately 50% of people exposed, sometimes indicated as ID50 (Schmid-Hempel and Frank, 2007). Thus, the disease is almost inevitable by exposure to even small amounts of raw WW. Pathogens with MID as few as 101 cells or particles include Shigella spp, E. coli O157:H7, many viruses, the protozoan parasites C. parvum and G. lamblia, and the helminthic parasites Ascaris, Necator, and Strongyloides. Most diarrheal illnesses are due to the ingestion of pathogens (fecal-oral route) (Bolbol, 1991). Still, direct contact with contaminated WW can also result in helminthic penetration through the skin (PHAC, 2010a, 2012), and inhalation of aerosols can lead to viral and some bacterial infections, notably Leptospira and Legionella (Medema et al., 2004; PHAC, 2001a).

Surveillance of WW sources for debilitating and easily spread pathogens such as poliovirus is routine in many developed countries (Anis et al., 2013). However, traditional detection methods are time-consuming and expensive. Thus, the presence of most pathogens is not routinely monitored (Bitton, 2011; USEPA/USAID, 2012; WHO, 2006), and precise concentrations are not always available. Instead, the FIB test generally verified the possibility of fecal contamination, which is the enumeration or mere presence of not necessarily pathogenic enteric bacteria (USEPA/USAID, 2012; Bitton, 2011; WHO, 2006).

The ideal indicator species possess the following characteristics: 1) It occurs where pathogens do, 2) it cannot grow in the environment, 3) it is more resistant to disinfection than pathogen, 4) it is easy to isolate and count, 5) it can be isolated from all types of water, 6) it is not subject to antibiosis, 7) it is specific to fecal matter, 8) it is found in higher numbers than pathogens, 9) the density of the indicator should relate to the degree of contamination, 10) the density of the indicator should relate to a health hazard (Griffin et al., 2001). Of course, a single ideal indicator organism does not exist (Blumenthal et al., 2000). However, using indicator organisms, such as E. coli and total coliforms, to monitor drinking water quality is, in most cases, a good approach (Edberg et al., 2000). There are several different organisms currently in use as FIB: mainly E. coli, but also Enterococcus (Noble and Weisberg, 2005; USEPA, 1986), Bacteroidetes (Gawler et al., 2007), and C. perfidiens spores (Payment et al., 2001a). However, fecal coliforms and E. coli are the most popular. Consequently, the fecal contamination tests are often reported as FC and E. coli colony-forming units (CFU) 100 mL-1 (WHO, 2006).

Disinfection options: Disinfection is usually performed by chlorination (or similar oxidative chemicals), which chemically disrupts the cellular integrity of pathogens (and other cells). Chlorine is abundant, dissolves easily in water, and persists for a long time as a residual, exhibiting disinfection properties at around 0.1-0.5 mg/L, which is safe for humans to consume. While chlorine is the gold standard of disinfection, it is a toxic chemical that can form gaseous chlorine at high pH, can create carcinogens in the presence of amines and organic matter (chloramines, organo- halides) and dosing levels may be hard to regulate in a decentralized setting (Sun et al., 2009; Zhang et al., 2011).

Ultraviolet (UV) disinfection is well-established for effluent treatment in large WWTPs (Nasser et al., 2006). The efficacy of UV disinfection is a function of the radiation that cells are exposed to since UV destroys linkages in DNA and other macromolecules. Clearwater (low turbidity) is more susceptible to UV disinfection. Previous studies using UV for disinfection combined with the NBS™ technology showed that 100% of Fecal Coli can be inactivated from NBS effluent when the radiation was at or above 10 mJ/cm2 (Fig. 1, Azaizeh et al., 2009).

Fig.1 - Effect of UV radiation on bacterial counts from NBS effluent. 3 log inactivation is the assay limit based on influent concentration

On the other hand, UV requires a delicate and expensive light bulb, a constant energy source, and a special housing chamber that could be broken or stolen in a rural setting.

Silver has been known to have antibacterial properties since Roman times; however, the increased. use of Nanosilver in a range of (as yet essentially) experimental drinking-water treatment systems, its Use in conjunction with ceramic filters and their perceived potential as a water disinfectant.

Silver and Ag nanoparticles (NP) have been shown to have general (i.e., not specifically water disinfection related) anti-bacterial properties against a range of both Gram-negative (e.g., Acinetobacter, Escherichia, Pseudomonas, Salmonella, and Vibrio) and Gram-positive bacteria (e.g., Bacillus, Clostridium, Enterococcus, Listeria, Staphylococcus, and Streptococcus) – Wijnhoven et al. (2009). Some researchers have also demonstrated that fungi, such as Aspergillus niger, Candida albicans, and Saccharomyces cerevisiae, are sensitive to silver (reviewed by Marambio-Jones and Hoek, 2010). In addition, several studies have suggested a biocidal action of AgNP against the hepatitis B virus (Lu et al., 2008), HIV-1 (Elechiguerra et al., 2005), syncytial virus (Sun et al., 2008), and murine norovirus (De Gusseme et al., 2010).

In terms of water-disinfection-related applications, silver is most commonly used in domestic water. filters (either to reduce the level of biofilm growth within the filter or as an additional level of Treatment). It is also quite commonly used in conjunction with copper ionization as a preventative Measure against colonization of Legionella spp. in hospital hot water systems. AgNP are currently Being tested in several experimental point-of-use (POU) treatment systems, ionic silver has been investigated for its potential for use as a secondary disinfectant (to reduce levels of chlorine) in Drinking-water supplies. Silver ions (in combination with both copper and chlorine) have also been She was investigated for use in swimming pool disinfection.

Quaternary Ions

The use of quaternary ions is accepted as a safe disinfection method by the Israeli Ministry of Health. It works by binding and disrupting bacterial cell membranes and is safe for human consumption. It can be produced as a granular material and a slow-release disinfectant.

The Natural Biological System™ is the most suitable technology for water treatment in small remote settlements due to its low construction cost, negligible operation and maintenance costs, no need for an electrical supply, easy adaptation to the environment, and no generation of byproducts and ability to stand fluctuations in quality and quantity of incoming water. The Natural Biological System fills the gaps in the remote and rural water treatment networks. To date, the NBS™ has been deployed in various settings ranging from industrial waste to polluted surface water and surpasses regulatory demands. The PNBS is the packaged, engineered version of the NBS. It is ready for point-of-use tailoring by adding dedicated fill suitable for final disinfection and taste improvement, according to prevailing regulations. The P-NBS gives a fast, efficient and economical solution even in places where it was thought that no other solutions were feasible. P- NBS is a modular water treatment technology based on the combined action of a tailored substrate, differing

Hydrologic profiles and biological components such as microbes and macrophytes. Through a thermodynamic cycle of solar, gravity, and biochemical energy, the overall process transforms the pollutants in the wastewater into sequestered and inactive forms, e.g., biomass, adsorption products of plants, and minerals. The result is a cutting-edge, “out of the box” competitive system that surpasses standard water treatment plant schemes.

Rapid deployment and Installation of the PNBS within one day in the Sacaba region, Bolivia.

  • The treatment system is designed to function without mechanical or human intervention, resulting in meager maintenance costs.
  • P-NBS can simultaneously treat a full range of contaminants (organics, nitrogen, phosphorous, metals, minerals, pathogens) and is a powerful buffer, absorbing high fluctuations in sewage quality.
  • Given its modular and portable nature, sewage can be treated as close to its source as possible, with minimal pipe systems and Contaminated drinking water sources can be treated on-site to supply unlimited clean water via a unique, efficient, and flexible hydrology regime.
  • The P-NBS™ is tailored to optimally treat water in a wide range of environmental conditions, including the level of potable water.

P-NBS needs neither aeration nor sludge removal systems, thus having a lower CAPEX than other water treatment systems. For the same reason, the OPEX of M-NBS is significantly lower than that of standard decentralized plants. This operational “simplicity” gives us advantages over any rival, especially in rural areas where they become “white elephants.”

Preliminary Results:

In 2014, an NBS™ was established to treat sanitary sewage from a power plant in Israel and is under continuous observation. The NBS™ removes contaminants from raw sewage to the tertiary treatment level, including a four Log removal of Fecal Coliforms. Hence the NBS™ effluent can be polished to drinking level by a short step consisting of taste improvement and disinfection.

Current Operations and investments:

Through more than 30 years of experience, Ayala has provided holistic solutions for urban and rural water treatment and supply and watershed rehabilitation through hundreds of projects worldwide. These include water harvesting and treatment for the supply of water to rural farms, villages, and homesteads, industrial wastewater treatment (textiles, refinery, olive, and wine mills, dairy farms, Landfills leachate, cosmetics, pharmaceuticals, and more), municipal wastewater treatment, “active” landscape engineering, flood prevention, lake rejuvenation, reservoir buffering. Ayala is a pioneer in modular, pre-fabricated Natural Biological System Technology and employs a multidisciplinary team with expertise in thermodynamics engineering, landscape architecture, biotechnology, agriculture, civil works, health, and financial planning. The company is led by Eli Cohen (CEO and commercial director of Ayala), a nature-based technology expert. Ayala serves as a consultant to the Inter-American Development Bank and the National Green Tribunal (Supreme Court of India) in Sustainable Wastewater Treatment and Water reclamation projects.

The PNBS has received preliminary funding to customize the internal aggregates from BRIGAID as part of the Horizon 2020 initiative to support innovations with a high promise to mitigate challenges posed by climate change. A broader description is available here:


A full-scale demonstration system was established at Ayala’s R&D headquarters in Zipori, Israel.

Ayala has joined with the industry in India to produce customized, expanded clay aggregate that can be used as a lightweight carrier for active supplements, such as pH modification and AgNP.