ON-SITE SANITATION

Commonly, on-site sanitation is equivalent to ‘household latrine’, but may also include facilities shared by several households living together on the same site. The more commonly known on-site sanitation includes facilities which are self-contained within the site, in contrast to sewerage where Sewage is removed from the site.

Amongst some sector professionals there is a general feeling that on-site sanitation is appropriate for rural areas and it is generally unsuitable in the urban context. In practice, given the continuous growth of urban populations and the high incidence of low-income people in slums and peri­urban areas, there is no possibility of providing all urban inhabitants with sewerage. Well maintained and constructed on-site/plot systems offer a viable alternative to sewerage system.

Requirements of On-site Sanitation

Requirements for adoption of on-site sanitation are:

• Adequate space for locating toilets and leach pits;

• Porous subsoil to absorb liquid content of excreta; and

• Groundwater at depth greater than 1.5 m from ground level.

Advantages and Disadvantages of On-site Sanitation

Advantages of on-site sanitation are:

• Simple to construct, operate and maintain;

• Less expensive to install and maintain; and

• Surface water pollution is eliminated

Disadvantages of on-site sanitation are:

• Not suitable for substrata with hard rock and high water table condition;

• Possibility of pathogens leaching into groundwater and contaminating it; and

• In densely populated urban areas crucial groundwater resources can get contaminated.

ON-SITE SANITATION TECHNOLOGIES

The following on-sanitation technologies are being used around the world:

1. Pit latrines
2. Ventilated Improved Pit Latrines
3. Composting toilets,
4. Ecological sanitation (Eco-san)
5. Two-pit Pour flush toilet
6. Pour-flush toilets to septic tanks

Pit Latrines

The use of pit latrines is extremely common in rural areas or amongst the poorer segments of society in developing countries. They are principally based on hiding human excreta in deep pits (drop and store), as opposed to flushing away and diluting them in rivers and lakes (flush and discharge). Pit latrines are designed for the onsite disposal of human excreta, with no or very little water use. They consist of a concrete squatting plate or riser, which is placed over an earthen pit. The design life varies from 5 to 10 years depending on the number of users. Often, the pits fill up faster than originally expected. The pit diameter is between 1.0 and 1.5 m. The depth of the pit is at least 2.0 m, but usually more than 3.0 m. The top 0.5 m of the pit requires lining. In loose soil, the entire pit should be lined in order to prevent collapse. The liquid (urine and water) content of faeces is normally designed to be absorbed into the soil. One unit can serve one or several households. Pit latrines are simple and relatively low cost but have many drawbacks as detailed below.

Disadvantages of Pit latrines

 

• Since pit latrines involve soil absorption of liquid and hence, there is a danger of groundwater contamination;

• They cannot be used at all in crowded areas, on rocky ground, where the groundwater level is high or in areas periodically flooded;

• They require access to open ground and digging of new pits or emptying of existing ones every few years;

• Emptying of pits can be very difficult (may require manual labour, and pits may collapse);

• Usually high level of odour and flies

• Toilets cannot be situated in houses, hence lack of privacy and safety concerns especially during night time

Ventilated Improved Pit Latrines

 

A conventional pit latrine can be upgraded to a ventilated improved pit (VIP) latrine. The VIP latrine is shown in  fig has a vent pipe to improve ventilation. These types of latrines are also often designed as a double-vault system, where one vault is left to dry, while the other vault is being filled. Drying of the faeces is also much less effective