In recent years, hospitals are significant consumers of water per day and generation of multiple amount wastewater from the hospitals has been increasing as a result of development in medical field. Sewage from hospitals which contains infectious and hazardous pollutants should be treated before its discharge into the drain.
1. What is Hospital Sewage and why to treat it ?
Generally, wastewater is defined as the composition of physical, chemical and biological waste present in wastewater. Hospital sewage is a wastewater generated relatively in larger quantities from all the units of the hospitals such as emergency and first aid, operating rooms, drug treatment, ICU, chemical and biological laboratories, radiology, canteen and laundry activities etc.
Since, hospital sewage/wastewater consists of various potentially hazardous components that will cause many risks on human and environment by polluting surface and ground water. Hence, hospital sewage treatment is very much required.
The major objective of hospital wastewater treatment plant is to treat the influent (untreated wastewater) generated by the hospitals and healthcare sectors before its direct release into natural environment. Hospital wastewater may have an adverse impact on environments and human health. Therefore, proper wastewater management in each and every hospital is prerequisite.
2. Hospital Sewage Characteristics :
Wastewater from various hospitals consists of :
1. Microbial pathogens and harmful bacteria and virus
2. Pharmaceuticals and its metabolites
3. Radioactive isotopes
4. Hazardous chemicals, heavy metals
5. Drug residues
3. Hospital sewage or wastewater treatment plant process :
Compact or packaged sewage treatment plant for hospitals is done in series of steps. Conventional treatment processes involved to remove impurities from the influent are listed below.
1. Preliminary Stage or Pretreatment : As a first stage, preliminary treatment process is essential in most of the sewage treatment plant (STP). It removes items such as sticks, rags and other large debris and heavy inorganic solids contained in the hotel influent through bar screens. Removal of these materials protects plant’s equipments from damage. The inorganic settled is called as grit which is removed using grit chamber.
2. Primary Treatment Stage : This is the second step in sewage treatment system. Physical separation of solids and greases from wastewater is done in this stage. Now, water flows into primary filter or clarifiers for few hours to allow solid particles to settle down and lighter particles will float to the top will be skimmed off from the tank. The settled solid is called as primary sludge or primary effluent contains about 60-70% of solids. Partly treated wastewater is now subjected to next treatment level.
3. Secondary Treatment Stage : It is a biological treatment process removes dissolved inorganic materials present in soluble and colloidal form from the wastewater. Here, bacteria are used convert the colloidal and dissolved organic matter. Now the partially treated wastewater from primary tank flows into the aeration tank and air is supplied through air blower to provide oxygen for microbes. When wastewater flows into secondary clarifier, where solids settle down which is called as secondary sludge and part of it is recycled for activated sludge process and remaining is mixed with primary sludge which will be send to sludge digestion tank and then disposes off. This stage removes about 90% of inorganic solids.
4. Tertiary or Advanced Treatment Stage : This is the last stage in most of the STP’s. This stage removes the suspended solids and organic matter which was not removed in secondary treatment. The pathogenic microorganisms which were not removed during biological treatment process will get removed by the process called disinfection. Several disinfection agents can be used depending on wastewater condition (pH, clarity etc). It is achieved by means of physical or chemical disinfectants like chlorine, UV light, ozone etc. Now, disinfected wastewater is suitable for disposal or reuse.
Conventional processes involved in Sewage Treatment Plant (STP) for Hospitals is shown below:
If the water is not treated adequately, the harmful contaminants in the sewage is hazardous to human health and natural environment. So, Sewage treatment Plant in hospitals is always necessary to reduce harmful impact on the environment.