The scope statement is divided in two main chapters: the project presentation and the project requirements. In that entrepreneurship part, our goals are:
Once all that points mentioned, the reflection about the design of the product can begin.
Cholera is a diarrhea-causing-disease that has affected the entire world through many epidemics throughout history. Today it still strikes developing countries, war-torn countries or those affected by natural disasters. It is contracted after ingestion of water contaminated with the pathogenic bacterium Vibrio cholerae. The main cause of a cholera epidemic is the lack of drinking water and sanitation resources in affected countries. According to the WHO, between 1.3 and 4 million cases are reported worldwide each year and 21,000 to 143,000 deaths.
Rehydratation is a very efficient treatment to cure the patients, however some people can not get this treatment early enough because they live in remote areas or can not have access to drinkable water. Thus a solution to treat water in these areas has to be found. Current preventive solutions (sterilizing filtration, water treatment by chlorination, etc.) are expensive or difficult to set up.
Our team wants to make a new system of detection and purification of water contaminated with the pathogenic bacterium Vibrio cholerae. This device will consist of two elements:
The device will be designed for local populations. Thus, the goal is to set up a system as suitable as possible to their users for the purification of water contaminated with cholera.
This project is run by a group of nine students from different universities: Paul Sabatier University (Toulouse), INSA Lyon and INSA Toulouse. It is supervised by Stéphanie Heux and Brice Enjalbert, researchers at LISBP (Toulouse), assisted by eleven other researchers. The team was formed in January 2017 and will work on this project until November 2017, date of the final restitution at the MIT, Boston.
Our system must detect the presence of Vibrio cholerae in water so that the antimicrobial peptides (AMPs) are spread in flow only if it contains Vibrio cholerae. In fact, the production of AMPs has to be controlled for two reasons. On the one hand, if water is drinkable, there is no need for AMPs production. On the other hand, other microorganisms (either from the user microbiota or the nearby environment) won’t develop peptide resistance.
To develop the disease, the minimal quantity of V. cholerae cells a human being must ingest is about 104 cells, in one dose of water
Detection is not the top priority of our system. Purification could work continuously but the implementation of this function is better for safety reason. Moreover, according to the testimonies, the detection function of our system is a new and strong point in the treatment of water contaminated with V. cholerae.
The other aim of our project is to wipe V. cholerae out of water. The system has to produce antimicrobial peptides when water is contaminated with V. cholerae, i.e. when water contains amounts of microorganism superior to the minimum toxic concentration (about 104 cells in one dose of water1). The AMPs used for the project have a broad spectrum of action against microorganisms, but they are particularly efficient against V. cholerae (Leucrocine I : MIC = 0.156 µg/mL3 (>52µg/mL4); D-NY15: MIC = 27 µg/mL4; cOT2: MIC = 29.22 µg/mL5). The goal is to produce these peptides until V. cholerae is wiped out and water becomes drinkable or usable without being dangerous.
Purification of water contaminated with V. cholerae is the central part of our project: the priority is high. Without it, which is the first goal of the project, the contract won’t be fulfilled.
The exchanges of molecules between the compartment containing GMMs and water must be feasible but the GMMs must not go into water. Actually, on the one hand, the CAI-1 molecule of the V. cholerae quorum sensing must diffuse to the compartment containing the detecting bacteria, V. harveyi. On the other hand, the AMPs produced by P. pastoris must go from the compartment containing the GMMs to the water contaminated with V. cholerae. However, class I GMMs must be kept out of the purified water.
GMMs must not be spread in the environment. The compartment containing them must be impact- and break-resistant. People need to be aware that GMMs should not be disseminated in the environment.
AMPs will be produced and released in water with the aim of wiping out V. cholerae. The amount of AMP remaining in water should not be toxic to humans. Experimentations must be done to know the quantity of AMPs in the water supposed to be drunk and especially their effects on epithelial cells (esophagus, stomach, intestines, etc.).
The proportion of nutrients should be correctly calculated so that they are all consumed during the lifetime of GMMs. An excess of nutrients in the compartment could then diffuse into the water and cause the emergence of new microorganisms.
As GMMs are used in this system, it is essential to think about their waste management. After the use of the GMMs for the detection of V. cholerae and the purification of water, they must be killed before throwing them away. The questions are: how to kill them and where to dump the GMMs?
In order to have an eco-friendly approach, the plastic used for the device must be recyclable.
GMMs (V. harveyi and P. pastoris) must be confined in the same compartment because they need to interact with each other. The microorganisms must be kept in this compartment. If they are freeze-dried, the water to be treated must be able to rehydrate the microorganisms. Therefore, water must be able to enter into the compartment.
To sum up, the compartment containing the microorganisms must hold them back but also, allow exchanges of CAI-1 molecules, AMPs and water between the two compartments of the device.
In developing countries, war-torn countries or those affected by natural disasters, people cannot possess a complex device from both a scientific and technical point of view.
The device must be easy to transport in order to reach the populations of remote villages or in conditions of natural disaster and armed conflict.
The treatment speed must be reasonable compared to the volume of treated water.
The water treatment capacity must be adapted to the device function and to the capacity of the microorganisms to detect and treat the water. According to Alama Keita (UNICEF), our device must be able to purify around 11,025 L of water in a week for a village.
The device has to be built with robust materials (refer to paragraph “Spreading of the GMMs”).
Water treatment must not modified its taste so that the product can be easily accepted.
The price must be adapted to similar options offered on the market.
Chloramine tablets are often used to treat water. In order to be competitive on the market, it is necessary to bring our price into line with our competitors. Therefore, to give us an order of magnitude, cost of chloramine tablets to treat the same volume of water as our product can be calculated.
The product “Chloramine 60 Tablets from SANOFI AVENTIS BELGIUM”6 contains 60 tablets of chloramine and costs 3.69€. According to the instructions, 1 to 4 tablets must be dissolved in 25L of water, depending on the water pollution degree. One tablet costs 3.69/60=0.0615€. Thus, treating 25 L of water costs up to 246cts (4 tablets) and up to 9.84cts for 1L.
To conclude, treating water with our system should not cost more than 10cts per L.
To conclude, the system must be able to detect V. cholerae and release AMPs from a threshold concentration of pathogenic bacterium in water. The water treatment aspect thanks to AMPs is essential.
The device that we have to create must gather technical criteria from an environmental, safety, material and economic point of view that we have listed in the scope statement. These specifications were defined taking into account the advice we received from the people we met throughout our project.
The design of the device will have to best fit these constraints to be accepted by our potential future customers.
Scope statement
Chapter 1 - Project presentation
Context
Purpose of the project
Organization of the project
Chapter 2 - Project requirements
Functional specifications
Detection of Vibrio cholerae
Description
Constraints
Priority
Purification of water
Description
Constraints
Priority
Technical specifications
Safety
Ingestion of the GMMs
Spreading of the GMMs
Human toxicity of the AMPs
Limiting media leaks
Environmental
Waste management of the GMMs
Recyclable plastic
Material
GMMs storage
Easy to use
Transportable
Treatment speed
Water treatment capacity
Strength
Water taste
Economical
Conclusion about the scope statement
References