Cover Page
Table of Contents
Executive Summary
The CSU Energy Institute has sponsored Team 22 to create a COVID wastewater sampler. The sampler is used to collect small temperature-controlled samples of wastewater to send to a COVID testing facility, and the data informs public health data and decisions. The sampler currently in use at CSU is problematic because it uses ice as a primary cooling method. The sampler is heavy, has poor temperature control, has a non-ideal sample rate, and requires operators to manually shake a bucket of wastewater. Team 22 was sponsored in an effort to create a new sampler with a focus on solving these problems.
The initial design had three iterations. All three iterations use peristaltic pumps to transport sewage into a primary tank which is cooled by a vapor compression cycle, powered by a 12V battery. Peristaltic pumps were chosen due to their excellent performance in systems with particles or high viscosities, and vapor compression was chosen due to its high coefficient of performance.
The first and second iteration had a 10 L primary tank with drainage lines. It would use a set of timed valves to fill four sample storage containers, then drain the contents of the tank while still in the sewer. This idea was justified because 10 kg of water be subtracted from the weight of the system as handled by the operators. The difference between the first two iterations is the valve system. The second iteration used a trapped volume valve system that dispensed exactly the same volume to each sample container. This was justified by removing the need for sensors on each container.
The third iteration of design saw two major changes. The first change was the switch from 10 L tank to a 1 L tank. This was justified by the energy savings on cooling. The second change was a switch away from valves to transfer from the primary tank to a sample storage container. Instead, a peristaltic pump was chosen due to reliability gain over a solenoid valve.
Presently, the third design iteration will work as follows. The sewage will be pumped through a strainer, occasionally reversing the flow to dislodge debris. When it enters the primary tank, it will be cooled by the vapor compression cycle. The collection and cooling will continue for 24 hours, at which point, the macerator will engage. The homogenized sample will be pumped through a second peristaltic pump to the sample storage container at the prespecified volume. This iteration has potential to be linked to a wireless function for a more seamless operation via remote control and communication of errors.
Introduction and Background
After the first outbreak of polio in epidemic form in 1894 in USA, Vermont with 132 cases, public-health authorities and organizations understood the limitations of the conventional monitoring of the disease and proved that it is incapable of preventing outbreaks. Therefore, a wide applications of wastewater surveillance began in the 1990s to eradicate the poliovirus, where the goal was to survey transmission dynamics of entire communities to be monitored because it costs less than testing individuals randomly without a plan, as it collects data from people and reveal infection dynamics earlier than diagnostic testing [1].
Covid-19 (SARS-CoV-2) which is also called coronavirus is a global pandemic that started spreading in 2019. The symptoms of the virus can sometimes lead to Pneumonia (lung infection), respiratory failure, heart problems, liver problems, and death [2]. During the COVID-19 pandemic, measures have been taken by communities to detect early signs of COVID in order to more effectively begin quarantine and targeted testing. A very effective method taken by CSU is the monitoring of wastewater with genetic analysis. A sampling system is used to collect wastewater samples which are sent to the laboratories for Covid-19 test. These tests can detect outbreaks before the nasal swab tests, which were the other primary method of testing [3]. Figures 1 and 2 show a comparison between the number of samples with Covid-19 and the number of the reported cases at the same period of time [4].
Figure 1: COVID-19 Virus in Wastewater Samples [4]
Figure 2: Reported COVID-19 cases by Onset Date [4].
This engineering team is helping CSU’s Energy Institute to develop a new wastewater testing system. The need for an improved wastewater sampler is fairly new. Previously, wastewater sampling was done on a broader scale, sampling high flow sewer lines for bacteria. However, in the wake of COVID-19, wastewater sampling has been used as an early detection system [3]. The demand for sampling has changed. The demand is now for a sampling machine that does genetic analysis on lines with both high and low flow rates [5].
The current sampling devices used by CSU are ISCO-6712 portable sampler, ISCO-GLS compact sampler, and Geotech auto sampler. All these devices include a peristaltic pump which uses a suction tube to suck up the wastewater from the sewer line, and a 4 Ah battery that is used as a power supply [6]. The peristaltic pump is connected to a control system where the desired sampling interval and sample volume are chosen. The wastewater is then stored in a 10L plastic (polyethylene) container that is kept on ice to prevent heat that can break down the virus and make it undetectable [6]. The required temperature for the samples is from 4°C to 6°C. The sampling systems are kept collecting samples for over 24 hours, and the samples are grabbed two times a week [6]. However, there are some problems and issues that face the sampling team while using those devices. They are considered heavy and big in size by the sponsor and the sampling team with a total weight between 60 to 80 pounds [4]. They require two people to lift them, and sometimes a winch is needed to lower the devices in the sewer line [4]. A problem that affects collection in the lower flow rate lines is the presence of solid waste, especially waste which doesn’t belong in the lines like Q-tips, rags, and plastic cups. This waste clogs the pumping system (strainer) of the device which stops it from pulling the samples [5]. Although ice is used to cool the system, ice needs to have additional housing in the system, ice adds more weight to the system, and ice temperature is difficult to control in a 24-hours period which causes it to melt. According to the sampling team, the desired samples temperature cannot be achieved with current cooling method “ice”. Another issue with using those kinds of samplers is that there will be large pieces stored in the 10L container which requires one person to shake the container before grabbing the samples. This is considered hazardous since it will increase the possibility of contact between the sampling team member and the wastewater. Figures 3 and 4 represent one of the sampling devices used by CSU [6].
Figure 3: Current Wastewater Sampling System at CSU [6]
Figure 4: Surroundings at a wastewater sampling site at CSU [6].
On the other hand, there are other sampling systems that are used for other applications rather than the wastewater sampling for Covid-19. One of those sampling devices is called the automatic water sampler. The automatic water samplers are suitable for different applications such as stormwater sampling, river sampling, surface water sampling, wastewater sampling, etc. [7]. Figure 5 clarifies the use of two types of the automatic water samplers with two different applications [7]. Furthermore, those devices are fully automated where the desired time interval and the sample volume can be entered in the menu [7]. Also, the automatic samplers include analytical sensors which make them able to detect high loads in water, then the samples will be collected automatically [7]. The automatic water samplers are beneficial since they help in protecting surface water, identifying discharges into sewage systems, and collecting samples for water management authorities and industrial customers [7].
Figure 5 :Liquistation CSF48 Sampler in wastewater treatment plant (A) and Portable Liquiport CSP44 Sampler in river sampling (B) [7]
Another current auto-sampler used is YSI Pro Sampler (Figure 6) that helps in detecting COVID-19 outbreaks in communities. It is designed for use in surface water, stormwater, and wastewater applications. It includes a 5 and up to a 30 meters hose to pump wastewater to a 10 liters container. The sampler is double-walled and insulated for longer ice retention. The Pro Sampler should be installed in a location where the sample temperature is between 0 °C and 40 °C. This product costs $3,250.00, and it is not meant to be put in sewer lines through manholes [8].
Figure 6: YSI Pro-Sampler P-12 and Pro-Sampler PM-12 (A) and Application/Installation of P-12 (B) [8]
Furthermore, YSI provides the automatic WS700 Series which is used to collect the samples directly from the sewer lines for Covid-19 detection (Figure 7). The sampler should be placed upright as it will not work if placed on its back or side. It includes a 15’ sampling hose, 1 or 2.5 gallon of polymer bottle, and a rechargeable battery. It can be installed along any part of the wastewater network including buildings. The autosampler can collect samples by composite sampling, discrete sampling, or by both simultaneously. However, it must be used during peak usage hours [9].
Figure 7: WS705 and WS700R [9]
Wastewater-based surveillance has gained prominence and come to the forefront as a leading indicator of forecasting COVID-19 infection dynamics owing to its cost-effectiveness and its ability to inform early public health interventions. A university campus could especially benefit from wastewater surveillance, as universities are characterized by largely asymptomatic populations and are potential hot spots for transmission that necessitate frequent diagnostic testing [10].
Problem Statement
Wastewater sampling systems were designed for wide applications such as the detection of pathogenic viruses in sewages such as COVID-19. It provides early warnings of virus outbreaks days before it shows up in nasal swab testing in the general population. Current system is a PCR sampling system that uses an auto-sampler to collect an effluent sample from the wastewater network for a targeted population. However, the current auto-sampler is heavy and labor intensive, where it requires a winch to lower and retrieve the auto-sampler from the manhole and it is filled with 10 liters of ice to cool the collected samples during the 24-hour period. Furthermore, the current auto-sampler does not work well with low flow rates because in low flow rates the suction system does not collect homogenized samples and the suction line that is responsible for carrying the fluid from the sampling point to the device gets plugged by debris and rags. Also, the current device collects 10 liters of wastewater and only 3 samples of 100 milliliters are taken for lab testing after the 24-hour period. Correspondingly, the current auto-sampler is large and cannot fit in many sewer lines.
Currently, the customers are interested in studying COVID-19 pathogens present in a population and whether the transmission is increasing or declining. For this project the customers are professors and laboratory technicians in the Microbiology department and Energy Institute at Colorado State University (CSU) who plan to make this project useful and ideal in different industries and facilities across the States. The customer’s stake in the solution of this project is their resources, time, and money. The end-users of this solution are rarely the same as the customers, where the end-users are the CSU’s wastewater surveillance team, in collaboration with technicians from mechanical engineering and microbiology departments at CSU.
There are many stakeholders involved in this project including agencies such as The Center of Disease and Prevention (CDC) and the US Department of Health and Human Services (HHS). Where guidance and regulations are released for public health, environmental, and academic laboratories, as well as state, local, territorial health departments to implement wastewater-based disease surveillance to eradicate the virus safely. Another stakeholder in this project is Colorado State University (CSU) as it is funded by Energy Institute to success and achieve the project goals and objectives.
Figure 8: Federal Partnering Framework for Wastewater Surveillance[14]
The project currently in the preliminary testing and building phase with concrete approaches to be implemented in depth to meet our objectives. The first approach is having a powered refrigerating system for the collected samples that will substitute the current cooling system which is crushed ice. The idea behind this solution will solve two big issues that the current device has. The dispense of the 10 liters of crushed ice will allow us to reduce the size and weight of the auto-sampler and cool the collected samples to the ideal temperature (4C° – 6C°), so the virus does not break down and maintain that temperature for 24-hour period.
The second approach is having a mixing system inside the tank that will house 6 liters of sample during the 24-hour period of suction from the sewage network. This device will consist of mixing paddles (impellers) mounted with a shat which driven by a motor. This solution is a safety approach, where in the current auto-samplers the wastewater surveillance team take the tank out of the device and shake it with their hands to have good mixed sample for lab testing. Considering the wastewater as a biohazard, having a mixing system inside the auto-sample would reduce the contact between the working team and the collected sample because it contains different viruses and bacteria.
Figure 1: Mixer Impellers and Flow Pattern [2]
Lastly, a self-cleaning (draining) approach has been considered in this project as it is one of the objectives. The auto-sampler has a peristaltic pump that transfers the fluid from sewage to the tank. Usually, the surveillance team take couple samples of 100 milliliters each after mixing the collected sample and then manually discharge the unwanted liquid back to the sewer line. However, in our approach the peristaltic pump is reversed remotely, and we would be able to empty the tank from the unwanted sample without any contact from the wastewater surveillance team, and 400 milliliters out of the 6 liters will be collected for lab testing.
Figure 2: Pumping Back to Sewage (CCW Rotation) [1]
Figure 2: Pumping Back to Sewage (CCW Rotation) [1]
Figure 3: Pumping to Tank (Clockwise Rotation) [1]
Figure 3: Pumping to Tank (Clockwise Rotation) [1]Objectives and Constraints
There are eight constraints the new sampler must comply with, shown in Table 1. The first constraint states that the sampler must sample for 24 hours to match the performance expectations of the current sampling technology. The next constraint sets the maximum sample at 6 degrees Celsius as the upper acceptable limit for the target value, as shown in Table 2, of 4 degrees Celsius. The maximum diameter constraint exists to ensure the sampler can fit inside of the manholes found around CSU. The exposure criteria exists because many of the sewer lines exist near or on sidewalks and roads; a submerged system will not face automobiles, bicycles, or curious pedestrian tampering. The sample storage criteria exists because the lab technicians requested a maximum sample amount of 200mL for storage and sampling. The constraints for spark generation and maximum system temperature exist because of the possibility of fire hazards. The gasses of concern, listed in Appendix XXX, will not ignite if kept below 200 degrees Celsius and away from sparks. The final constraint is to not go over budget for the Energy Institute. The new constraints are exposure and max system temperature. These were added to address concerns of oversized and readily combustible systems, respectively.
Table 1: Constraints for the sampler
Constraints
Description
Metric
Limit
Operation time
Amount of time expected for continual sampling
Hours
24
Max Sample Temperature
Maximum allowable sample temperature
°C
6°C
Max Diameter
Max diameter to easily fit in the manhole cover
cm
50
Exposure
Amount of the sampler expected to be above ground
% Exposure
0%
Sample storage
Amount of sewage sample that must be stored at a low temperature
ml
200
Spark generation
Spark and flame are explosive hazards in a sewer line.
Number of sparks
0
Max System Temperature
The max temperature at any point is limited to avoid the autoignition of flammable gasses
°C
200°C
Budget
Maximum money spent
Dollars
2500
There are seven objectives for the new sampler, shown in Table 2. The size objective is in place to reduce awkward handling and transportation of the sampler. The weight objective is in place to reduce injury. Current OSHA regulations use an equation, shown in appendix XXX, to determine the maximum lifting weight of an item. The contact potential objective is in place to reduce safety hazards with sewage contact. The maceration objective is in place to eliminate the dangerous job of shaking the primary tank. The battery power objective is in place to reduce the cost and weight of the sampler. The only new objective is the battery objective, which was added to avoid spending large amounts of money on a battery.
Table 2: Objectives for the sampler
Objective
Description
Priority
Metric
Objective Direction
Target
Size
Size of the whole sampler
1
cm³
min
15x15x30
Weight
Weight of the whole sampler
5
kg
min
23
Contact potential
Operator contact with raw samples during use or misuse
5
Number of contacts
min
0
Timer resolution
The resolution of the digital timer
4
Seconds
min
30
Error storage
The amount of storable error codes
4
Number of codes
max
50
Has Maceration
Macerating homogenizes the sample
3
Y/N
max
Y
Battery power consumption
Amount of power consumed at steady state operation
5
W
min
10
Design Summary and Design Decisions
After obtaining the initial list of the objectives and constraints, the first iteration of design was performed using a combination of morphology and Pugh chart analysis. Emphasis was placed on the refrigeration aspect of the design, with the morphology chart (Appendix XXX) having six methods of cooling. A large goal in the design process at this stage was finding a suitable replacement for ice cooling, due to the unacceptable sample temperature with ice over a 24 hour period. In order to quantitatively compare the refrigeration methods, a new objective was added: Battery power consumption. The full Pugh analysis as seen in Appendix XXX-XXX yielded the system form as displayed in table 3.
The first iteration of design specified a 10L primary tank capacity, which presented problems in the weight objective. Assuming a density of sewage to be equal to the density water, the 10L tank would add roughly 10kg of weight to the system, accounting for nearly half of the 23kg weight objective. The solution for this was to include a redundant primary tank drain. After the 24 hour period, the primary tank would receive maceration, deposit samples to the smaller sample containers, and then open the primary tank drains. This design allowed the 10 kg sample to be excluded from the weight criteria because the operators would only remove the sampler from the manhole after the sampler had expelled the tank contents.
A peristaltic pump was selected for the pumping between the sewer and the tank. The peristaltic pump was chosen because it is a positive displacement pump which allows for precise intake control. The peristaltic pump also excels in pumping fluids with high viscosity or high particle count, which is the target sample for this sampling system
Table 3: The design decisions after the first design iteration
Function
Form
Cooling
Vapor compression refrigeration
Sample storage
Primary tank design with four-valve transfer and primary tank drain
Control of tank transfer
Combination: level sensor, camera, open loop valve control
Energy storage
12V Battery
The second iteration of design began with concerns relating to tank transfer control. The fundamental assumption of the first design iteration was that the sampler remained in the sewer until the primary tank drained. This presented a problem that the operators could not diagnose or fix any problems while the sampler was inside the manhole. The first design iteration attempted to fix this by having two redundant systems, namely a camera and a level sensor, but this added eight points of failure, more mass, and more of an energy demand. To fix this, a system of nozzles, as shown in figure 11, was implemented such that control of the valves became unnecessary.
Figure 11: The second iteration’s constant volume nozzle design. The cup is attached to a brace that moves vertically to seat the cup around the nozzle. When the cup is seated, the solenoid valve is opened until the system returns to rest, then the solenoid valve is closed. The cup is then slowly lowered, allowing the sewage in the nozzle to enter the cup.
During the second iteration, a focus of design was on strainer clogging. The proposed solution for strainer clogging was a reverse flow system where the peristaltic pump has its polarity switched in order to pump some sample backwards through the strainer, dislodging any large objects blocking a hole.
The battery was also sized during the second stage of design. Two thermodynamic equations were used to size the battery. Equation 1 dictates the energy required to lower the sample temperature
Q = m cₚ ∆T (1)
Where Q is energy to cool the sample [J]; m is the mass of the sample, assumed to be 10 [kg]; cp is the specific heat of the sample, assumed to be 1486 [J*kg-1*K-1]; and ΔT is the change in temperature, assumed to be 25 [K]. This yielded an energy of 371.5 kJ or 8.6Ah at 12V.
Equation 2 dictates the steady state cooling rate that must be applied to the sample to remain at the desired temperature
Q̇= h A ∆T (2)
Where Q is the cooling rate [W]; h is the overall convective coefficient, assumed to be 5 [W*m-2K-1]; A is the surface area [m2], calculated as a cylinder with a diameter of 40cm; and ΔT is the steady state temperature difference, assumed to be 25 [K]. This equation yielded a cooling rate of 43.9 W, which over a 24 hour period requires 87.8 Ah (at 12V) of energy storage. The overall energy storage demand was therefore calculated as 96.4 Ah for just the refrigeration needs, and the battery size for the second design iteration was consequently chosen at 100 Ah.
The second design iteration also saw a relocation of the battery. It was decided that the battery would reside at the top of the manhole, just underneath the sampler brace. Electrical lines would run along the length of the structural wire to the battery box, with an operator using a connector at the end. The purpose of this change was to exclude the unacceptable weight of a 100 Ah battery from the rest of the sampler. Some deep cycle batteries with 100 Ah capacities were hitting the 23kg objective, which would make the sampler unacceptable in terms of weight.
The third iteration of the design began with concerns over battery capacity and solenoid valve practicality. A battery undergoing full discharge will deteriorate much quicker than a battery that only hits 50% depth of discharge. The 100Ah battery would be prone to deterioration, especially when considering the extra loads from the pump and solenoids. A large goal of the third iteration was to reduce the energy load from refrigeration. This was accomplished by altering three factors: the mass of the tank, the surface area of the tank, and the heat transfer coefficient. The mass was reduced from 10kg to 1kg, the diameter of the tank was reduced from 40cm to 10cm, and the tank gained a criteria for insulation, reducing the heat transfer coefficient estimate from 5 [W*m-2K-1] to 2 [W*m-2K-1]. These changes reduced the cooling energy storage estimate from 96.4 Ah to 7.72 Ah.
The change to a smaller tank had other benefits. It removed the need for tank drain lines due to the lower mass an operator would be required to lift. It also reduces the average flow rate of the pump from 6.94 mL/min to 0.694 mL/min.
The concerns over solenoid valves were not limited to the electric power draw; there were concerns about valves closing in a fluid with small particles such as a sewage sample. This failure would present a safety hazard and a tedious cleanup effort, resulting in a score of 900 on a FMEA. A second peristaltic pump was chosen to fix that problem as well as give the operator a custom input for the desired sample quantity.
Final Design / Concept
Geometric Modeling
Each part in the assembly is shown in figure 12 and described in table 4. All models are shown without piping intact; instead, the piping routes are highlighted in matching colors. Figure 13 shows the sampler in the “ready” state, as it would be found inside the sewer. Figure 14 shows the components of the sampler without the housing or lid. Figure 15 shows the lower level components from the same angle with the tank removed to reveal the sample storage container and the expansion valve.
Table 4: The labeled parts from figure 12
Part
Description
1
Lock bar
2
Heat exchanging lid
3
Microcontroller
4
Macerator motor
5
Bracket for parts 3 and 4
6
Compressor
7
Sample storage container
8
Expansion valve
9
Tank lid
10
Tank
11
Pump brackets
12
Peristaltic pump (x2)
13
Housing unit
Figure 14: The sampler view with no lid or housing
Figure 12: The exploded assembly of the sampler, labeled in Table 4
Figure 13: The assembled sampler Figure 15: The lower level of the sampler with no tank
Most components in the sampler are available as ready-made components or assemblies. The housing can be purchased as a 10 gallon drink cooler; the refrigeration components can be purchased as an assembly and modified to fit the housing; the peristaltic pumps can be purchased; the 1L vacuum cooled tank can be modified from a readily available coffee container. The pieces that need custom fabrication are all the interior brackets, the lock bar, and the lid supports. The metal equipment can be formed with bending and drilling, and the brackets can be formed with a mill functioning as a drill press.
Preliminary Feasibility Analysis
The main concern regarding feasibility of the sampler is battery energy storage. The sampler should not exceed 50% depth of discharge on the 30 Ah battery. The sampler uses energy for the following functions: refrigeration, pumping, microcontroller and control panel, and maceration. The energy used by each process can be calculated by equations 3-7, with constants found in table 5. The energy is then converted to Amp Hours given a voltage of 12 V.
Qtotal = Qcooling + Qpumping + Qcontrol + Qmacerator (3)
Qcooling = m cₚ ∆T + ∆t (h A ∆T) = 44580 J + 66.8 Wh = 92.6 Wh = 7.72 Ah (4)
Qpumping = 2 m g z = 78.48 J = 0.0218 Wh = 0.0000231Ah (5)
Qcontrol = ∆t (0.6 [W]) = 14.4 Wh = 0.0810 (6)
Qmacerator = (10 seconds) (300 W) = 3000Ws = 0.833 Wh = 0.0694 Ah (7)
Qtotal = Qcooling + Qpumping + Qcontrol + Qmacerator = 7.87 Ah at 12 V (3)
Table 5: Constants used in the energy equations governing battery size. The surface assumes a 10cm diameter and a 1 L volume
Symbol
Meaning
Value
Unit
M
mass
1
kg
cₚ
specific heat of water
1486
J/ (kg K)
∆T
change in temperature
30
K
∆t
operation time
24
hours
H
overall convective coefficient
2
W/ (m²K)
A
surface area for 1L
0.0557
m²
G
gravitational constant
9.81
m/s²
z
height difference
4
m
This estimation is conservative for the following reasons. The cooling estimation assumes a coefficient of performance of one which is lower than standard vapor compression refrigerators; also the convective heat loss is calculated over the 24 hour period with the assumption of a full tank. The Arduino control estimation assumes a power draw of 0.6 W, which is roughly twice the power requirement of a standard Arduino. The macerator energy usage is calculated with a 300W residential blender motor designed to crush ice; it is unlikely the macerator motor in this application will require such power.
The energy consumption estimate of 7.87 Ah fulfills the depth of discharge recommendation, with enough spare battery energy to run again in an emergency scenario.
Design for X
The sampling device will be mainly used by the wastewater sampling team at CSU and possibly by other organizations that are interested in tracking Covid-19 using wastewater. Therefore, the system will be designed for being smaller in size compared to the current systems, lighter in weight, and easier to use. Also, the device will be fully automated where the users will have to only program the control system such as choosing the sampling time interval, the sampling volume, the time desired to start the sampling process, etc. The two peristaltic pumps will be programmed to function automatically during the 24 hours period. The first pump will continue collecting the wastewater samples depending on the desired sampling interval, where the second pump will automatically transfer the wastewater collected from the 1L container to the small centrifuge tube at the end of the 24 hours period. After 24 hours, the user will simply pick up the centrifuge tube that contains the homogenized representative sample which is ready to be tested in the lab. Finally, the product will be built so it can meet customers’ needs and requirements. This device is expected to be cheaper compared to the current sampling devices.
Primary Components and Budget
The budget for this project is $2500. Currently, the team only has only purchased two of the items on the budget estimation: the housing and the sample storage containers. There are no anticipated expenses related to research, competition registration, or travel. The budget allows approximately $1000 for unforeseen expenses.
Table 6: The projected expenses to make a sampler. The only items currently purchased are the plastic housing and the sample storage containers
Item
Cost [$]
Batteries
200
Wires
30
Sheet metal
150
Cleaning products
20
3d printing filament
25
Arduino
25
Hoses (vinyl)
50
CNC machining labor
300
Remote controls
30
Integrated circuits
50
Cables
20
Pump/motors
100
Peristaltic pump
100
Maceration blades
100
Refrigeration components
200
Insulated tank
50
Plastic housings
47.70
Sample storage containers
29.72
Total
1527.42
Risk Analysis and Management
Project Related Risks
There are some risks expected in the process of building the sampling system which can create challenges to the team and affect the completion of project on time. The first risk is related to the project budget provided by the sponsor. The team members should be concerned about not exceeding the designated budget. Before any purchase, the team members will discuss the item needed to be obtained, will make sure it is important and satisfies project goals, and finally inform the project sponsor about the purchase. Covid-19 is another risk that could be a threat to the group member’s health. All members are required to follow Covid-19 health guidelines provided by the state and CSU to achieve a safe working environment. Furthermore, time is considered as one of the main challenges associated with completing the project. The team is required to complete the project by the E-days. To be able to meet to the requirement, a project plan has been already created by the team members which consists of tasks and objectives for the two semesters with the expected time duration to complete each task. A preliminary Gantt chart was created to manage and monitor the project progress. The Gantt chart includes an estimation of the duration needed to complete each task. Also, the team is meeting with the assigned GTA weekly and the project sponsor bi-weekly to make the sure the project procedure is on track. On the other hand, building and dealing with the sampling system can be dangerous. The sampling system includes electrical components that could cause electric shock if not used properly. All group members should be conscious about some electrical hazards such as poor-quality wiring, working with wet hands, etc. Each group member will make sure to understand the connections between the electrical components and how they work to prevent electrical risks. Another risk related to the sampling device is wastewater. As known that the device will be used to collect wastewater and sewage samples that contain bacteria, viruses such as Covid-19, funguses which are harmful and can cause diseases. There are some health instructions will be followed by the group members when dealing with wastewater such as wearing gloves, wearing masks, etc. Finally, the lack of human resources could be a challenge to the team. The team should keep in mind that the loss of a team member is expected during the semesters. For example, a team member might drop the class or withdraw from college. As a result, an additional work will be expected from the rest of the team members in the project. Even if this situation happened, the tasks will be splitted equally among the team members while the members remain confident to complete their project as was planned. The team members are also expected to support and help each other when facing extra challenges due to the member loss. The project sponsor and the GTA will be informed by the team about any occurring problem to find a suitable solution.
Technical Failure Modes and Effect Analysis (FMEA)
The areas of highest risk in the design are all related to sewage transfer. This is mostly due to some of the complications in pumping sewage, including safety hazards and small particles in the transfer lines. A large safety margin is built in the fact that operators are still expected to arrive daily to collect samples. A brief inspection occurs during the retrieval process.
Table 7: FMEA for the sampler system
Validation / Test Plan
Work Plan
The work plan is needed in the procedure of designing and building our sampling system since it helps to organize the tasks required to achieve the project goal. However, as the project continues, some tasks and objectives are expected to change as group members have started to have a deep understanding about the project requirements. Also, the expected time durations to complete some tasks have been updated. The work plan for this project is still divided into three phases that are distributed in two semesters. A preliminary Gantt chart was also created to manage and monitor the project progress. The Gantt chart includes an estimation of the duration needed to complete each task. The three phases are listed below followed by the Gantt chart. The completed tasks in the work plan are labeled with the word “Complete” in the phases list.
Phase 1 (Complete)
Define problem statement [Complete]
Project background research [Complete]
Analyze the current sampling system [Complete]
Identify objectives and constraints [Complete]
Phase 2 (In progress)
Brainstorm for the new sampling design [In progress]
Build a design prototype [Not started]
Test the prototype (initial test) [Not started]
Evaluate the prototype during initial test [Not started]
Phase 3 (Not started)
Modify the design
Test the modified system
Make extra modifications if feasible
Final test
Iterative design
Figure 16: Wastewater Sampling System updated Gantt Chart
To make sure the project is on track and being completed on schedule, there are some methods used to encourage group members participations and decisions making. Google Drive is the main platform used by the group as a workspace and to share files. All work done related to project either it was a group or individual work is uploaded in google drive. Some examples of work uploaded include design diagrams, calculations tables, Pugh charts, class assignments, etc. In addition, during each meeting, a team meeting minutes form is used by the project manager to record the agendas discussed and the decisions made by the group which can be used as a reference in the future. Those meeting forms also include the jobs assigned to each team member and the deadline date to complete each job. The meeting minutes forms are included in the appendix section of the report. Furthermore, the group is scheduled to meet the assigned GTA weekly on Tuesdays to discuss the project progress including the tasks accomplished, project challenges, and what the group is planning to work on. Similarly, the team is expected to meet the project sponsor bi-weekly to get some feedback and to provide the sponsor an overview of the project progress.
In the first semester, the project’s problem statement has been identified by the group, and a background research was done to understand the history and the domain of the project. The next step of the plan was analyzing the current sampling system to understand how it functions and to identify its problems and disadvantages. After the analysis of the current sampling device, a list of objectives and constraints that should be considered to meet the project requirements was established by the group. Based on objectives and constraints, the team has started brainstorming for the new sampling design to finally end with the suitable design idea. During the brainstorming process for the design prototype, there are some tools and methods used for the engineering analysis such as design diagrams and energy estimations for the cooling system. Tables XXX and XXX show the calculations made for the energy estimation of the cooling system. Table XXX demonstrates the calculations made to estimate the heat energy required to keep the wastewater cool for a 24 hours period. While table XXX represents the calculations for the power required to keep the sample cool for a 24 hours period. Moreover, the team has started purchasing some components that will be used to build the sampling system such as the centrifuge tubes.
Table XXX: Calculations to cool a 1 L sample of water at a delta of 30 degrees K. A delta of 25 is highlighted because it is expected to be the most common cooling requirement.
Table XXX: Calculations to determine the cooling rate of 1 L sample of water at a delta of 30 degrees K. A delta of 25 is highlighted because it is expected to be the most common cooling requirement. The cooling rate is in Watts, but it is converted into 12V amp hours with the assumption of a 24 hour run time.
The team was not able to start building the design prototype this semester as planned. This is due to more time than expected being spent by the group brainstorming and iterating for new design prototypes. As a result, the building process will start next semester.
For the second semester, a design prototype will be built. The group will continue purchasing the required components for building the prototype including peristaltic pumps, a power supply “battery”, Arduinos, tubes (hoses), vacuum-insulated cooler, etc. The sampling system prototype will be prepared for an initial test, and then will be evaluated based on its performance during the test. After the performance analysis, the sampling device will be modified and tested until it meets the project requirements and sponsor standards. The group is expected to have a complete modified sampling system during the E-Days that can operate as needed. At the end of the semester, a final test will take place in a sewer line on campus to ensure the sampling system functions as desired.
Conclusion
An innovative solution is necessary for a better operation and sampling system of the auto-sampler. There are several constraints and objectives that must be considered to collect an ideal sample for lab testing and data analysis. The auto-sampler must keep the collection of samples during the 24-hour period in a cold temperature of 6°C to prevent the virus from breaking. Creating a safe refrigeration system is the most difficult part as the auto-sampler is exposed to flammable Hydrogen Sulfide with an autoignition of 232°C [13] and explosive Methane inside sewer lines which can result in an unsafe environment for the wastewater surveillance team.
References
(Bryce’s are labeled starting at 1001 for easy relabeling)
[1] “Watson-Marlow Pumps: Brands: WMFTG,” WatsonMarlow. Available: https://www.wmftg.com/en-us/brands/watson-marlow-peristaltic-pumps/.
[2] Peters, S., 2021. Introduction to Mixer Impellers & Flow Patterns. Blog.craneengineering.net. Available at:
Figure 10: [14] “Federal Coordination and partnering for wastewater surveillance,” Centers for Disease Control and Prevention, 23-Jun-2021. [Online]. Available: https://www.cdc.gov/healthywater/surveillance/wastewater-surveillance/federal-coordination-partnering-wastewater-surveillance.html. [Accessed: 03-Oct-2021].
[1001]
“Common Noxious or Dangerous Gases Encountered in Sewers,” Document Center, 20-May-2014. [Online]. Available: https://www.springfieldmo.gov/DocumentCenter/View/495/. [Accessed: 24-Nov-2021].
[1002]
“Fuels and chemicals – autoignition temperatures,” Engineering ToolBox, 2003. [Online]. Available: https://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html. [Accessed: 24-Nov-2021].
[1003]
Cincinnati Ohio 45226, T. R. Waters, V. Putz-Anderson, and A. Garg, Cincinnati, OH: U.S. Dept. of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Biomedical and Behavioral Science, 1994.
[1] D. A. Larsen and K. R. Wigginton, “Tracking covid-19 with wastewater,” Nature News, 21-Sep-2020. [Online]. Available: https://www.nature.com/articles/s41587-020-0690-1. [Accessed: 12-Sep-2021].
[2] N. Pathak, Coronavirus and COVID-19: What You Should Know, August 23, 2021. Accessed on: September 5, 2021. [Online]. Available: https://www.webmd.com/lung/coronavirus
[3] B. Roberts, “Proposed Projects,” in MECH 486 Engineering Design Practicum, 26-Aug-
2021.
[4] B. Roberts, “COVID Wastewater Sampling System,” presented to MECH 486A – Engineering Design Practicum 1, Colorado State University, Fort Collins, CO, USA, August 24, 2021. [PowerPoint slides]. Available: https://colostate.instructure.com/courses/129014/pages/project-showcase-preparation?module_item_id=3962506 , Accessed on: September 5, 2021.
[5] B. Wilson, “Sponsor Meeting,” 09-Sep-2021.
[6] CSU COVID Wastewater Sampling Team, Colorado Water Center, May, 2021. Accessed on: September 5, 2021. [Online]. Available: https://watercenter.colostate.edu/spotlights-csu-covid-wastewater-sampling-team/
[7] Automatic water samplers, Endress +Hauser USA. Accessed on: September 6, 2021. [Online]. Available: https://www.us.endress.com/en/field-instruments-overview/liquid-analysis-product-overview/automatic-water-samplers
[8] “Autosamplers for covid-19 outbreak detection,” Water Sampling for COVID-19 Detection. [Online]. Available: https://www.ysi.com/covid-wastewater-sampling#. [Accessed: 12-Sep-2021].
[9] xylem, “WS Series Autosamplers for COVID RNA.”
[10] Smruthi Karthikeyan, A. Nguyen, D. McDonald, Y. Zong, N. Ronquillo, J. Ren, J. Zou, S. Farmer, G. Humphrey, D. Henderson, T. Javidi, K. Messer, C. Anderson, R. Schooley, N. K. Martin, Rob Knight, School of Medicine, A., and D. McDonald, “Rapid, Large-Scale Wastewater Surveillance and Automated Reporting System Enable Early Detection of Nearly 85% of COVID-19 Cases on a University Campus,” mSystems, 31-Aug-2021. [Online]. Available: https://journals.asm.org/doi/full/10.1128/mSystems.00793-21. [Accessed: 13-Sep-2021].
Figures and Tables
Figures 1 & 2: [4] B. Roberts, “COVID Wastewater Sampling System,” presented to MECH 486A – Engineering Design Practicum 1, Colorado State University, Fort Collins, CO, USA, August 24, 2021. [PowerPoint slides]. Available: https://colostate.instructure.com/courses/129014/pages/project-showcase-preparation?module_item_id=3962506 , Accessed on: September 5, 2021.
Figures 3 & 4: [6] CSU COVID Wastewater Sampling Team, Colorado Water Center, May, 2021. Accessed on: September 5, 2021. [Online]. Available: https://watercenter.colostate.edu/spotlights-csu-covid-wastewater-sampling-team/
Figure 5: [7] Automatic water samplers, Endress +Hauser USA. Accessed on: September 6, 2021. [Online]. Available: https://www.us.endress.com/en/field-instruments-overview/liquid-analysis-product-overview/automatic-water-samplers
Figure 6: [8] “Autosamplers for covid-19 outbreak detection,” Water Sampling for COVID-19 Detection. [Online]. Available: https://www.ysi.com/covid-wastewater-sampling#. [Accessed: 12-Sep-2021].
Figure 7: [9] xylem, “WS Series Autosamplers for COVID RNA.”
Figure 16: M. Al Ghassani. “Wastewater Sampling System updated Gantt Chart.” Updated: November 17, 2021
Tables XXX and XXX: B. Christensen. “Energy estimations for cooling system.” Updated: November 22, 2021
Appendix
Table XXX: The autoignition temperatures [1002] given for gasses commonly found in sewers [1001]
Gas
Autoignition Temperature [C]
Ammonia
630
Carbon Dioxide
Non-combustible
Carbon Monoxide
609
Ethane
515
Gasoline vapor
246
Hydrogen
500
Hydrogen sulfide
232
Methane
580
Nitrous oxides
Non-combustible
Sulfur dioxide
Non-combustible
Table XXX: Maximum lifting weight for continual use, used by OSHA [1003]
Equation
RWL=(23 kg)*HM*VM*DM*AM*FM*CM.
Variable
Definition
RWL
Recommended weight limit
HM
Horizontal multiplier
VM
Vertical multiplier
DM
Distance multiplier
AM
Asymmetric multiplier
FM
Frequency multiplier
CM
Coupling multiplier
Table XXX: Morphology template
Function
Idea 1
Idea 2
Idea 3
Idea 4
Idea 5
Idea 6
Cooling
Ice
Compressor fridge
Thermoelectric fridge
Propane fridge
Liquid nitrogen
Dry ice
Energy source
Battery
Supercapacitors
Generator
Sample storage
One big tank only
Big tank feeding little bottles
Little bottles only
Tank transfer
4 separate valves
Rotating tank with 1 valve
Rotating bottles with 1 vavle
Pouring spout
Table XXX: Pugh analysis for cooling methods
Concept 1
Concept 2
Concept 3
Concept 4
Concept 5
Concept 6
Criteria
Weight
Baseline
Ice (current baseline)
Compressor fridge
Thermoelectric fridge
Propane fridge
Liquid nitrogen
Dry ice
Power consumption
4
0
0
-2
-5
-4
0
0
Size
1
0
0
-2
5
-3
2
0
Weight
5
0
0
-1
-2
-5
-3
-1
Contact potential
5
0
0
1
1
0
0
0
Timer resolution
4
0
0
0
0
0
0
0
Error storage
4
0
0
0
0
0
0
0
Maceration
3
0
0
0
0
0
-1
-1
Electrostatic filters
2
0
0
0
0
0
0
0
Constraints
Pass=0
Fail=-1
Operation time
50
0
0
0
0
0
0
0
Max Sample Temperature
50
0
-1
0
-1
0
0
0
Max Diameter
50
0
0
0
0
0
0
0
Sample storage
50
0
0
0
0
0
0
0
Spark generation
50
0
0
0
0
-1
0
0
Max System Temperature
50
0
0
0
0
-1
0
0
Total
-50
-10
-70
-144
-16
-8
Table XXX: Pugh analysis for sample storage
Concept 1
Concept 2
Concept 3
Criteria
Weight
Baseline
One big tank
Big tank feeding bottles
Little bottles
Power consumption
4
0
0
0
0
Size
1
0
0
-2
3
Weight
5
0
0
0
0
Contact potential
5
0
0
3
3
Timer resolution
4
0
0
0
0
Error storage
4
0
0
0
0
Maceration
3
0
0
0
-5
Electrostatic filters
2
0
0
0
0
Constraints
Pass=0
Fail=-1
Operation time
50
0
0
0
0
Max Sample Temperature
50
0
0
0
0
Max Diameter
50
0
0
0
0
Sample storage
50
0
0
0
0
Spark generation
50
0
0
0
0
Max System Temperature
50
0
0
0
0
Total
0
13
3
Table XXX: Pugh analysis for tank transfer control
Concept 1
Concept 2
Concept 3
Criteria
Weight
Baseline (N/A)
Level sensor
Camera footage
Open loop seconds control
Power consumption
4
0
0
-1
0
Size
1
0
0
-1
0
Weight
5
0
0
-1
0
Contact potential
5
0
0
0
1
Timer resolution
4
0
0
0
0
Error storage
4
0
0
0
0
Maceration
3
0
0
0
0
Electrostatic filters
2
0
0
0
0
Constraints
Pass=0
Fail=-1
Operation time
50
0
0
0
0
Max Sample Temperature
50
0
0
0
0
Max Diameter
50
0
0
0
0
Sample storage
50
0
0
0
0
Spark generation
50
0
0
0
0
Max System Temperature
50
0
0
0
0
Total
0
-10
5
Table XXX: Pugh chart for energy storage
Concept 1
Concept 2
Concept 3
Criteria
Weight
Baseline (4Ah)
Battery
Supercapacitors (x500)
Generator
Power consumption
4
0
0
0
0
Size
1
0
0
-5
-4
Weight
5
0
0
-4
-5
Contact potential
5
0
0
0
-3
Timer resolution
4
0
0
0
0
Error storage
4
0
0
0
0
Maceration
3
0
0
0
0
Electrostatic filters
2
0
0
0
0
Constraints
Pass=0
Fail=-5
Operation time
50
0
0
0
0
Max Sample Temperature
50
0
0
0
0
Max Diameter
50
0
0
0
-5
Sample storage
50
0
0
0
0
Spark generation
50
0
0
-5
-5
Max System Temperature
50
0
0
0
-5
Total
0
-275
-794
For each meeting there is a team meeting minutes form. One of the meetings forms is posted.
Team Meeting Minutes
Design Organization: MECH486 Senior Design
Date: 11/2/2021
Agenda:
Design prototype
Construction
Cooling system
Strainers
Discussion:
1- Using dry ice for one year — $430 / Dry ice can explode in closed systems.
2- A combination of electric ice chest and regular ice.
3- Is the battery inside or outside the system?
4- Battery life depends on the depth of discharge
5- Using 1 battery with a 100 Ah capacity for power supply — approx. $180.
6- All current strainers used are almost the same in design (stainless steel).
7- 3 strainers system / a strainer with impeller/ strainer with blade + motor combination (blender).
8- Strainer system — wastewater N-pump technology (Flygt impeller).
9- Housing shape — cylindrical (round) vs rectangular.
10 – Housing material — PE double walled (2 layers) for temperature control (insulator).
11- Autosampler with 3 sections is more organized.
12- The peristaltic pump is the suitable pump for the autosampler design.
13- Silicone hoses (tubes) are preferable to use with the peristaltic pump.
Decisions Made:
1- Continue the research for the design prototype.
Action Items
Person Responsible
Deadline
Strainers research
Wail Alkindi
11/4/21
Cooling system research
Bryce Christensen
11/4/21
Construction research
Mohamed Al Ghassani
11/4/21
Team member: Wail Alkindi
Date for next meeting: 11/4/21
Team member: Bryce Christensen
Team member: Mohamed Al Ghassani
Team member:
Team member:
The Mechanical Design Process Copyright 2018, David G. Ullman