Rhys E. Probyn
Ecological Sanitation
Unit 2 Assignment
11/12/2012
Unit 2.1
1. Helminths are parasitic __________ .
a. Mites
b. Flies
c. Worms
d. Protozoa
2. Which of the following does not contribute to pathogen reduction during urine storage?
a. Natural increase in pH as urea is degraded
b. Natural increase in temperature as urea is degraded
c. Time away from host organism
d. Increasing ammonia concentration over time
3. How long should source separated urine from centralized sanitation systems be stored at
temperatures between 4-19 C prior to fertilizing food crops for raw consumption?
a. No storage necessary
b. 1-3 weeks
c. 3-5 weeks
d. 1-6 months
e. 7-12 months
4. Which of the following statements about urine storage is incorrect
a. At temperatures below 20 C some pathogens are reduced at a very slow rate.
b. Lowering ammonia concentrations below 40 mM will reduce the rate of pathogen
inactivation.
c. Some losses of nitrogen are possible during storage.
d. All of the above statements are correct.
e. All of the above statements are incorrect.
5. Which of the following is neither a primary or secondary aim of urine treatment
a. To remove nitrogen by volatilizing ammonia to the atmosphere.
b. To kill viruses and pathogens.
c. To enable safe reuse without polluting or endangering public health.
d. To generate economic returns from reuse practices.
6. Struvite is__________.
a. An environmentally toxic byproduct of urine storage.
b. A corrosive compound in urine that attacks metal pipes and vessels used for transport
and storage.
c. A slow release fertilizer that precipitates naturally in stored urine but can be produced
in greater quantities by adding magnesium.
d. None of the above.
7. Which of the following “Exotic” uses of urine was not presented in this lecture:
8.
9.
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14.
a. As a mild lubricant for bicycle repair
b. As an insecticide simultaneous to use as a fertilizer
c. Human consumption (drinking) for medicinal purposes
d. A wound disinfectant
e. A source of the human fertility hormone HCG
What are the primary aims of Faeces treatment?
a. Pathogen reduction and protecting public health
b. Enabling safe reuse
c. Answer A only
d. Answers A and B
What are the secondary treatment aims for Faeces?
a. Volume reduction
b. Odor reduction
c. Pollution prevention
d. Appearance alteration
e. All of the above
Which of the following techniques is not used to kill pathogens in faeces?
a. Storing
b. Chlorinating
c. Composting
d. Drying
Which of the following statements about reducing pathogens in Faeces is incorrect?
a. No secondary treatment option provides 100% pathogen removal. (Incineration does,
this one might constitute cruel and unusual punishment)
b. At temperatures of 2-20 C up to 2 years of storage time may be needed to achieve
acceptable pathogen reduction for reuse.
c. At pH of 9 and above, 6 months of storage may be sufficient to achieve acceptable
pathogen reduction for reuse.
Which of the following are not included in grey water:
a. Baths and showers
b. Roof drainage (maybe to cruel, but also maybe incorrect. What do you think?)
c. Sinks and Dishwashers
d. All of the above are included in greywater.
As a rule of thumb treated greywater (from low cost treatment methods) can be used for
anything that does not require potable water quality. An example of an activity that should not
employ treated greywater is __________.
a. Laundry
b. Showering
c. Irrigation
d. Cooking
Explain why separate greywater treatment may be preferable to conventional mixed sewage
treatment and give two reasons why this may be attractive in some regions?
a. Easier to treat greywater: lower BOD (easily degradable too), lower Pathogens, Lower
total and ammonia N.
b. Drivers could include: overall water scarcity, potable water scarcity/cost, lack of proper
infrastructure (slide of open drains in Dhaka), groundwater recharge
15. Give one example of both a low rate and a high rate biological greywater treatment technology
and provide at least one pro and one con for each.
a. High rate: Trickling filter, MBR, RBC, conventional AS, bioaugmented AS (such as RDN),
Granted some of these would be overkill for greywater but they would work.
i. Ex. MBR1. PRO- Very high effluent quality (high reuse potential though additional
disinfection may be necessary), low land requirement,
2. CON- High capital and O&M costs, med/high operator skill needed
b. Low rate: Constructed wetland, facultative ponds, Septic tanks, UASB + sand filters
i. Ex. Constructed Wetland
1. PRO- Reasonable capital and O&M costs, reasonable effluent quality,
aesthetically pleasing, low operator skill needed
2. CON- High space requirement, effluent may need further treatment and
disinfection prior to reuse
16. Which of the following greywater treatment technologies achieves disinfection:
a. Sand Filters
b. Constructed Wetland
c. Membrane filtration (UF or NF +RO)
d. Granular Activated Carbon
Unit 2.2
1. Give 2 examples of common “non-improved” and 2 examples of common “improved” on site
sanitation practices?
a. Non-improved: bucket latrine, flying toilet, open defacation
b. Improved: pit latrine (ventilated or not), pour flush latrine, water flush toilet (with septic
tank, holding tank, or cess pit/pool), aqua privy with septic tank, UDD (technically not
common but I’d count it)
2. Explain what a flying toilet is and give at least one reason why they may pose risks to public
health: (I actually put this one on the first bi-weekly trivia sheet that I put out in my dorms
shared kitchen)
a. It is a plastic bag that you defecate in and throw away.
b. They can easily break or spill, clog drains, and are in general dangerous to anyone who
comes in contact with them.
3. Explain why bucket latrines may pose high risks to public and sanitation worker health:
a. Users must handle the buckets and pour the contents into holding vessels which must
be emptied by sanitation workers. Each manual transfer poses the potential for direct
human contact with pathogens. For example, splashing or spilling of contents, improper
4.
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safety equipment (see slides), or handling of unsanitary buckets themselves. This is a
minimal barrier approach to sanitation.
List at least 5 typical problems commonly associated with pit latrines
a. High Odor, fly breeding, overflowing, pit collapsing, pollution of groundwater, improper
use (rubbish dumping as well), difficulty digging new pits (urban areas), difficulty
emptying pits, must be outdoors.
What is a simple pit latrine and what are the primary differences between them and VIP and
pour flush latrines?
a. A simple pit latrine is a toilet (usually in an enclosure) above an unlined pit that collects
faeces and allows liquids to infiltrate into the ground.
b. A VIP has an added ventilation pipe with fly screens to reduce both odor and fly
breeding.
c. A pour flush latrine has a U-shaped pipe that creates a hygienic seal with water and
isolates the user from the odor and flies that may be in the pit. As its name implies it
should be periodically flushed with a (few) liter(s) of water.
Why is it advantageous to line the top of a latrine pit and not the bottom?
a. By lining the top you may be able to prevent the latrine from collapsing into the pit. By
lining the bottom you will inhibit liquids from infiltrating into the ground and may lead
to the pit filling up with liquid and overflowing.
A cess pit is:
a. Another term for a pit latrine
b. A holding tank connected to a water-flush toilet
c. An unlined pit connected to a water-flush toilet
d. A pit latrine constructed over a septic tank that can also receive greywater
An Aqua-Privy system is:
a. Another term for a pit latrine
b. A holding tank connected to a water-flush toilet
c. An unlined pit connected to a water-flush toilet
d. A pit latrine constructed over a septic tank that can also receive greywater
Draw a septic tank and explain how it works and what processes take place inside of it:
a. Usually a multiple chamber impermeable tank connected to a water-flush toilet that
combines settling, skimming, and anaerobic digestion. It maintains a constant water
level because as new excreta enters “treated” water overflows out into the leaching
field. Effluent quality is not very good.
b. Requires periodic (5-10 year) emptying
10. Name at least two technologies that produce faecal sludge “on-site” and briefly describe a
ecosan approach for off site management of this faecal sludge:
a. Pit latrines, septic tanks, bucket latrines, cess pools, aqua privies, etc.
b. Pit or tank emptying (pumping), truck transport to treatment facility, treatment
(settling, biological treatment, composting, etc), use as soil conditioner to grow food for
human consumption.
11. How does a UDD toilet work?
a. Urine is diverted to a storage tank and faeces drop into a separate ventilated storage
vault where it dries and shrinks in volume.
12. Give 2 advantages and 2 disadvantages of a UDD compared to a simple pit latrine:
a. Advantages; no pit required, less odor, suitable for high density settlements, areas with
compacted or rocky soil, susceptible to groundwater pollution, easier excreta recycling,
easier FSM (no vacuum truck needed)
b. Disadvantages: requires user education, odor problems when misused, dried faeces
need frequent removal, anal washing requires a separate vault, urine collection, storage
and transport needed.
13. Is a UDD always the better on site sanitation option?
a. Not necessarily, one must take into account local conditions, social, technical, economic,
environmental, public health, regulatory and institutional factors. In some cases it may
be more beneficial to opt for a VIP latrine, Aqua privy, water-flush/septic or pit, etc.
Unit 2.3 Storage and Transport Logistics
1. Explain what factors need to be considered in order to determine the appropriate size (V,
volume) for a household urine storage tank.
a. V= N * P * T
b. N = number of people in the household
c. P= Urine production per person per day (1.3 L /cap/day)
d. T= storage time between emptying
2. Though technologically simple, urine storage can be a major cost item for large scale ecosan
projects. Please explain.
a. Using the equation V= N * P * T and factoring in larger populations and total storage
time needed to sanitize urine it becomes clear than a large storage volume is essential.
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This will require numerous large volume storage vessels which can constitute a high
capital investment to purchase, transport to the site, install and periodically replace.
Collection and transport of urine can also be very labor intensive and expensive.
During the degradation of Urea CO(NH2)2 in stored urine the increase is pH is primarily due to
the generation of what Ion?
a. 𝐻𝐶𝑂3−
b. 𝑁𝐻4+
c. 𝐻2 𝑂 (not even an Ion)
d. 𝑂𝐻 −
Underground urine storage tanks and piping (especially connections) must be carefully
sealed when installed in order to avoid what?
a. Water intrusion
b. Anaerobic conditions
c. Microorganism introduction
d. Aerobic conditions
Explain the primary reason that urine pipe length and 900 bends should be minimized while
slope should be highly positive.
a. The longer urine runs through the piping system the more urea will be hydrolyzed
(by bacteria) and struvite ppt/sludge will be formed eventually leading to clogging.
Precipitates also tend to accumulate at sharp bends so avoiding them is beneficial.
Maintaining high slope will keep the flow velocity high and allow urine to carry
more solids to the storage vessel thus cutting down on pipe clogging.
When choosing a urine storage vessel which materials should be used and which should be
avoided? Explain why?
a. Metals should be avoided because urine is very corrosive.
b. Plastic tanks and ditch liners and rubber bags are acceptable but may be damaged
by exposure to direct sunlight (UV)
c. High Quality Concrete is acceptable but may be expensive.
d. Allegedly farmers can store it directly in the ground without a liner but this may
pose additional health and environmental risks (for example groundwater
pollution).
Type 2 Faeces, also call black-water consists of how much water per defecation?
a. 0.5 L
b. 1 L
c. 2 L
d. 3 or greater L
Type 3 Faeces, also called brown-water consists of how much water per defecation?
a. 0.5 L
b. 1 L
c. 2 L
d. 3 or greater L
Transportation and handling of excreta is a critical point of health risk during sanitation.
Please explain at least 3 measures that can be taken to minimize these risks.
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a. Protective clothing (gloves, shoes/boots, breathing apparatus)
b. Vacuum tankers large or small to avoid manual handling when possible
c. Sealed storage and transport containers (drums)
d. Hand washing
Large-scale transportation of urine is logistically quite difficult. Give a few reasons why and
propose at least one creative potential solution.
a. Long distance piping is difficult due to clogging tendencies
b. Road transport leads to increased traffic, CO2 emissions, noise pollution, and is
economically tied to the price of fuel thus distance of transport must be limited.
c. Solutions (these may not work but at least they’re ideas)- antimicrobial piping,
addition of “stabilizer” to urine (like fuel stabilizers to mitigate ethanol ↔ water
equilibrium in gasoline in the US), development of urban agriculture practices,
centralized urine treatment to ppt all available phosphorus then pipe remaining N
rich solution out of town, etc.
What do primary and secondary transport refer to?
a. Primary transport is the transport of excreta from the households or public facilities
where it is generated to a transfer point where it is collected and then undergoes
secondary (bulk) transport to treatment facilities.
What are 3 possible excreta collection vehicles and what are 5 factors that can be used to
determine which is most appropriate?
a. Vacuum tanker, tricycle (with or without motor), tractor drawn trailer, animal
(horse or ox) drawn trailer
b. Population density, road condition (surface, gradient, width), hauling distance,
waste density and quantity, availability of spare parts and service, traffic type and
density, waste hazardousness, etc.
Give at least 3 reasons why a vacuum pump may not be best suited for bi-weekly household
urine collections? Assume 4 people in each household
a. Heavy and Expensive- requires a generator to operate and likely needs a tractor to
pull.
b. Requires a metal tank to hold up to the vacuum. Remembering that urine is
corrosive this may not be a good long term solution
c. Urine is not very viscous thus a vacuum is overkill
d. The amount of urine created by 4 people over 14 (~73-84 L) days can be handled
fairly easily with a hand pump.