PROPOSED SEWERAGE & TREATMENT SYSTEM

Introduction

The present system is that the hospital produces black water that is being disposed of without any treatment. This black water is very contaminated and carries bacteria etc. Water from the washing facility in the hospital is also disposed of outside the compound without any treatment. The waste water from the houses and other buildings on the compound go into a septic tank near the house, on through to a sink pit and is then disposed of inside the compound or dumped over the cliff.

The waste water from Bhusaldada village is disposed in the same gulley where the black waste water of the hospital is being disposed of.

The facility that produces this contaminated water is the hospital. Since hospitals are established in order to care for the health of people, it is evident that a hospital should not dispose of contaminated water in a way that creates a possible health hazard to people. It is therefore of utmost importance that the waste water of the hospital is treated in such a way as to prevent people from getting sick if they come into contact with this waste water. This is even more important as people fetch water from springs in the neighborhood of the “waste water gulley”

The management of the hospital requested me to design a waste water cleaning system to end the situation where the waste water of the hospital pollutes the environment. As there are no waste water systems in Tansen with a second line treatment it will be used as an example for Tansen and Nepal.

I used to work for a Water Board in The Netherlands and I asked them to make proposals. This Water Board, HDSR (www.hdsr.nl), manages 17 waste water plants in sizes from the city of Utrecht (340.000 inhabitants) to small villages. They suggested three options for a waste water system:

  1. Septic tank with wetlands.
  2. A Sequencing Batch Reactor (SBR), a state of the art waste water system.
  3. A fully automated SBR, named ICEAS.
  4. A fully automated MBBR system.

Septic tank with wetlands

The advantage of solution 1 is, that it is simple with technology that is known in Nepal. The septic tanks have to be cleaned every 5 to 10 years and this is a known process. With this solution, no energy is required as the system works on the free flow of water. The wetlands need minimal maintenance. The quality of the effluent of the wetlands is up to international standards. The disadvantage is, that no chlorines for cleaning can be used and that it needs a bigger area of land.

A Sequencing Batch Reactor (SBR),

The advantage of solution 2 is, that it is an industrialized way of the process. It is compact and gives a good quality of effluent. The disadvantage is that it is more difficult to maintain, expert staff is needed and a lot of energy is needed to keep the process going. Maintenance people will have to be trained to be able to operate the system. Another disadvantage is, that this system gives a daily volume of sludge that has to be removed and brought to drying beds. The hospital doesn’t have room for drying beds and the transport equipment isn’t available in Nepal. It is costly to make and maintain such a vehicle only for use of this one waste water plant of the hospital.

An automated SBR, named ICEAS

The third option is even more complicated than option 2 and therefore beyond the possibilities of the hospital.

Automated MBBR system

After the design of a system with a wetland it appeared that a wetland will be expensive due to the high price of sand. We came than across a system invented by a Norwegian professor that is being used in the Scandinavian countries and several other countries worldwide. This systems appears to be good alternative for the wetland. A Dutch research institute (STOWA ) investigated this system and is positive about this cleaning system. It consists of two chambers with pumps and aeration. In one of the tanks they have flooding plastic particles. The system needs about 7,5 kWh of electricity. It produces sludge that is dewatered and has to be disposed of. However the investment costs are a fraction of the costs for a wetland. An American Company (EEC – www.eecusa.com) build this system in a container and works automatic. They have a manufacturing company in India.

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