RURAL SANITATION

&

SANITARY LATRINE

Building Services 1

Reference:

Water supply & Sanitation: Chapter 12by-

M.Feroze Ahmed and Md. Mujibur rahman. ITN- Bangladesh, BUET.

Week 13: Class 27 and 28

Introduction:Sanitation may be defined as the science and practice of effecting healthful and hygienic conditions and involve the study and use of all sorts of hygienic measures.

The word sanitation actually refers to all conditions that affect health.

Sanitation system with respect to human waste management involves following functions.

01. Excretion and storage.

02. Collection and transportation

03. Process/ treatment and

04. Disposal/recycle

Sanitation Systems

Sanitation also contributes greatly to preventing the spread of infectious diseases.

Classification of Sanitation Systems1. Basing on the location of storage treatment and disposal sanitation system

is classified as

01. On-site sanitation and

02. Off- site sanitation.

02. Basing on the methods of collection and conveyance of wastes sanitation system is classified as

01. Dry system and

02. Wet system.

03. Depending on whether the system allows infiltration or not, sanitation system is classified as

01. Permeable system and

02. Confined system

On-site Systems: When wastes are collected, treated and disposed off at or close to the point of generation, it is called an on-site system. Examples include: pit latrines and septic tank system.

Off-site systems: When wastes are colleted and transported away from the point of generation for treatment and disposal, the system is called off-site system. Examples include: bucket latrine system, conventional sewerage system.

Dry Systems: When no water is required for dilution or conveyance of waste then it is termed as dry system. e.g. Pit latrine (on-site), Bucket latrine (off-site).

Wet systems: When wastes are transported away using water as conveying media and water is used for dilution then it is termed as wet system, e.g. septic tank system (on-site) and conventional sewer system (off-site).

Permeable Systems: The system which allows infiltration of liquid portion of wastes into the ground; e.g. Pit latrine

Confined systems: The system which does not allow infiltration; e.g. septic tank.

Classification of Sanitation Systems

HYGIENIC LATRINE• A “hygienic latrine” is defined as a sanitation facility the use of which effectively

breaks the cycle of disease transmission.

• A hygienic latrine would mean to include all of the following:1. Confinement of feces, 2. Sealing of the passage between the squat hole and the pit to effectively block

the pathways for flies and other insect vectors thereby breaking the cycle of disease transmission, and

3. Venting out of foul gases generated in the pit through a properly positioned vent pipe to keep the latrine odor free and encourage continual use of the hygienic latrine.

FOOD FAECES(focus of

infections)

WATER

SOIL

FLIES

FINGERS

MOUTH

Faecal-Oral Routes of Transmission of Diseases

LOW-COST SANITATION TECHNOLOGIES for RURAL AREASMajor technological options are:

– Pit Latrines.– Pour Flush Latrines.

• A pit is simply a hole in the ground into which excreta falls. Urine and other liquids soak into the ground and solid materials are retained and decomposed in the pit.

• All forms of pit latrines are not fully sanitary. With slight modifications in design and with some interventions, conventional pit latrines could be improved to be hygienic.

Pit Latrines:

The major types of pit latrines include:• Simple or “Home-made” Pit Latrines• Ventilated Improved Pit (VIP) Latrine• Reed Odourless Earth Closet (ROEC)

• The simplest “home-made” latrine is built by digging a small hole and placing a bamboo platform on it

• One can use a concrete squatting slab and a ring for an improved version

• This option, though not fully sanitary is sometimes promoted to discourage open defecation

Compacted earth

Ground level

Infiltration of liquid

Earth

Super structure

CoverSquatting Slab

Pit

Accumulated solids

SIMPLE OR HOME-MADE PIT LATRINES

TYPES OF PIT LATRINES

Accumulatedsolids

Pit

Direct Pit

Accumulated solids

Water Sealed Trap

Pit

Earth

Offset PitPartially Offset Pit

Pit

Accumulat-ed solids

Slab with squat hole

Solids accumulation

Vent pipe

Pit lining

min. 300 mm

Fly screen

Superstructure

Liquid infiltration

Ventilated Improved Pit(VIP) Latrine

TYPES OF PIT LATRINES

01. Direct pit latrines: Some risk in the stability of the superstructure particularly when the soil underneath is loose and when the pit is submerged during the wet season.

02. Partially offset pit latrines: Relatively stable.

03. Offset pit latrines: Most stable and safest of the simple pit latrine options; may or may not include water seal with the pan.

04. A VIP latrine is an improvement over the simple pit latrine.The most important design variation in VIP latrine is the inclusion of the vent pipe and the fly-screen, which keep the latrine free from flies, mosquito, and unpleasant odors.

• ROEC, commonly used in southern Africa, is a variation of VIP latrine

• In ROEC, the pit is fully offset and is connected to the squatting plate by a curved chute.

• Advantages: The offset pit can be made larger (i.e., longer life); pit can be easily emptied; structurally more stable and aesthetically more acceptable

• Disadvantages: The chute easily becomes fouled with excreta, thereby providing a site for mosquito breeding and odor nuisance and making maintenance difficult.

Chute

Liquid Infiltration

Accumulated solids

Concrete cover

Vent pipe

Air

Seat

Air

Fly screen

Reed Odorless Earth Closet (ROEC) Latrine

Operation & Maintenance of Pit Latrines

Regular cleaning of the squatting slab with some water and a little disinfectant if available. In case of ROEC, the chute has to be cleaned regularly.

• A tight fitting lid should be placed on the squatting hole after every use to ensure insect and odor control. But in case of VIP latrines, the squat hole should never be covered to ensure continuous airflow; rather the door of superstructure should be kept closed for keeping inside dark.

• Some water should always be available in or near the latrine for cleansing.• Ash or sawdust can be sprinkled occasionally in the pit to reduce smell and

insect breeding.• Non-biodegradable material like stones, glass, plastics, rags etc. should not

be thrown into the pit as they reduce the effective volume of the pit.

Emptying of Pits

When the contents of the pit reach the level of 0.5 m below the slab, there are two options: –construction of a new pit on an adjacent site, or –emptying the existing pit.

Manual Emptying: involves serious health hazard.Mechanical Emptying: easier if the pit contents are wet.

POUR FLUSH Latrine• Further improvement over simple pit latrine• The most vital part is the “water seal”

incorporated between the squatting plate and the pit, which prevents unpleasant odor and insects from entering the latrine compartment

• An important precondition for such latrine is availability of some water (about 3 to 5 liters) for cleansing and flushing.

(1) Direct Pit Pour Flush Latrine

Types of POUR FLUSH Latrine

(2) Offset Pit Pour Flush Latrine(1) Direct Pit Pour Flush Latrine

(2) Offset Pit Pour Flush Latrine

(3) Alternating Twin Offset Pit Pour Flush Latrine

Types of POUR FLUSH Latrine(3) Alternating Twin Offset Pit Pour Flush Latrine

Suitability of Pour Flush Latrines

• Pour-flush latrines may be used in both rural and urban areas.• Single pits may be appropriate in urban areas only if they can be desludged

mechanically, since their contents are not pathogen free. Twin-pits are recommended if the pits are to be desludged manually.

• In rural areas mechanical desludging is neither reliable nor affordable. Consequently, pits should be designed for manual desludging.

• When the pit is full, a new pit can be dug and the superstructure, and the squatting slab can be placed over the new pit.

• The filled-up pit can be covered with some soil and left for a sufficient period of time before it can be emptied again for reuse.

• Alternating twin offset pit pour-flush latrines offer a much better solution if they can be afforded. If twin-pits cannot be afforded during the initial construction, the pipe layout and the first pit can be so placed so as to allow for the installation of a second pit when the first becomes full.

Measures to be taken for Pour Flush Latrines

The users shall take following measures for good performance of such latrine:

• the water seal must be maintained at all times in order to effectively control odour and insects,

• flow must be diverted to the second pit when the first pit is full, • the pit when full must be kept covered for at least one and a half year for risk

free manual emptying, and • that pour flush system may be upgraded to a septic tank system with a

soakaway or connected to a small bore sewerage system where available.

Advantages of Pour Flush Latrines

• Less expensive compared to conventional latrines (with sewerage systems)• Offer appropriate and hygienic solution for excreta disposal• Require low volumes of water for flushing, (2-3 litres/flush only)• Can be upgraded to connect to a sewer system or septic tank system• Eliminate odour, insect and fly breeding• Safe for children• Can be located, if desired, inside the house• Potential for resource recovery using the sludge as soil conditioner• Easy construction and maintenance of single pit pour-flush latrine

Operation & Maintenance

Important operational aspects include the followings:

• After each use, the pan is flushed with a few litres of water.• No solid material that could obstruct the trap should be thrown into the pan.• The floor and the squatting pan should be cleaned daily.• Wastewater from bathing and washings should not be drained into the pit.

Important maintenance aspects include the followings:

• Squatting pan and the trap have to be checked regularly for cracks.• In case of twin leach pits, the diversion box should be checked for blockage

and cleaned if necessary.• Single pits have to be abandoned and covered with 0.5 m soil when full, or

emptied by mechanical means.• In twin pit system, the user should regularly monitor the level of contents of

the pit.• If one pit is full, the other pit has to be emptied and made ready for use.• The pipe leading to the full pit must be sealed within the diversion box, and

the flow diverted to the empty pit.

PIT LATRINES FOR AREAS OF DIFFERENT HYDRO-GEOLOGIC CONDITIONS

• There are areas where modifications of usual design of different types of pit latrines is needed to make them appropriate. Such areas include:

• Dry Areas• High Groundwater Table Areas, and• Wet or Flood-prone Areas

DRY AREAS

• In dry areas (depth of WT 7 m or more), the least costly solution can be simple pit latrines with or without water seal. Here chance of groundwater pollution is minimum

• Single-ring or Multiple-ring pit latrines can be used in dry areas

• When multiple rings are used, gaps are provided between rings (with brick blocks); but this may cause stability problem

• Perforated rings or honeycomb brick walls are most appropriate for better infiltration of liquid

HIGH WATER TABLE AREAS• In water table areas, where deep excavations are not possible, a possible

solution is building raised pits; part of the pit remains below ground level, while part remains above ground

The portion above the ground must be made impervious above and immediately below the ground in order to avoid ingression of surface water or exfiltration of pit liquidPit liquid infiltration is achieved through the lower part of the pit below ground levelTwo types: Step latrine and Mound latrine.

Such latrines are also suitable for areas where deep excavations are not possible due to hard rock bed near ground surface

WET AND FLOOD-PRONE AREAS

• A major challenge• Where surface or groundwater

needs to be protected from pollution, pits can be enveloped with 500 mm fine sand

• One method of sanitation in swamps is to lower concrete rings below the bottom of the water body; has the disadvantage of filling up of the pit too soon.

Class Test: 04

01. Draw and show details of a inlet of rainwater down pipe. 2

Results of Assignment:

Time 30 min. Marks-10

02. What are the catchment areas in a building from where we can collect rainwater. 4

03. What are the technolgies that are adopted for using rainwater for various purposes. 4

13 th Week, 23.11.08,