Sewage or wastewater is liquid from residences, institutions, commercial and industrial establishments, together with groundwater, surface and storm water.
Nowadays, many hotels are not connected to a main sewerage hence installing sewage treatment plant for your hotels is a major criteria. Why because, Sewage treatment plant also called as wastewater treatment plant or water pollution control plant will take only few hours to remove most of the pollutants from sewage/wastewater before it is released into the natural environment or reuse. Sewage or wastewater from hotels undergoes few treatment processes to remove the majority of solid and organic material before it is clean enough to be safely discharged into waterways. After treatment, the treated water can be reused for gardening or can be disposed off.
The major purpose of STP for hotels is to treat the wastewater influent so that it will not cause dangerous diseases to humans. Wastewater from the hotels is collected in the treatment plant, where it goes through several stages of treatment by means of drains and collectors. The effective sewage treatment plants for small, medium and large sized hotels and resorts are very small and compact which involves mechanical, chemical and biological treatments/techniques which would minimize environmental pollution (i.e. water pollution).
Conventional treatment process flow chart for STP (in Hotels) is shown below :
Basic treatment steps involved in sewage treatment plant for hotels are as follows :
1. Preliminary Treatment : This treatment is the first step in processing waste water which is also called as mechanical/physical treatment process which needs to be done previous to primary treatment. During this stage, solids are removed through screening, sedimentation and skimming. It’s major objective is to remove coarse solids through screening. Incoming wastewater called influent passes through mechanical screens consisting of bars where rags, sticks, papers, drinking cans and other similar items will get removed. It involves grit chamber to remove sand and grit. This treatment also removes excessive amount of oils and greases. It is essential for preventing damages to the pumps and other equipments in rest of the treatment processes.
2. Primary Treatment : It is also known as physical-chemical treatment which is to be done prior to biological treatment called secondary treatment. It aims at removing organic and inorganic solids by the processes of sedimentation and floatation. Partially treated wastewater from preliminary treatment is allowed to pass through tanks called primary clarifier or sedimentation tank. During this treatment flow of wastewater is reduced to encourage sedimentation and thereby allowing the heavier solids to settle at the bottom and significant amount of floating material such as grease and oil will rise to the surface and be skimmed off. The settled solid is called as primary sludge which will be further subjected to sludge digestion process. This particular treatment removes about 50-60% of influent suspended solids and reduces BOD level up to 30-40%. The clarified water flows on to the next step of treatment.
3. Secondary Treatment : This treatment is referred as biological treatment process which generally uses one of the biological aerobic processes called “Activated sludge process” to degrade organic matter. During this process, primary effluent enters into aeration tanks, where it is mixed with microorganisms. Air is pumped into aeration tanks and hence bacteria growth will get increase to breakdown the organic matter that still present in the effluent. Now aerated wastewater flows into secondary clarifier where heavier particles and other solids settle to the bottom as secondary sludge. Some of the sludge will be re-circulated back to aeration tank to stimulate activated sludge process to remove as many pollutants as possible. The remaining sludge is removed from the tank and mixed with primary sludge in sludge processing system for further processing. This stage removes about 80-90% of organic solids. Once the water moves out of this stage, it enters into last stage called tertiary stage or disinfection stage.
4. Tertiary Treatment : It is the final stage in small sewage treatment plant which involves physical, chemical or biological processes to remove any residual or remaining suspended solids and dissolved solids. Even after primary and secondary treatment, treated wastewater may contain some disease causing microorganisms and that is why disinfection is required. Disinfection disinfects and kills harmful microorganisms from the effluent and it is done by using disinfectants like chlorine, ozone, UV light or other chemical disinfectants. Ozone and ultraviolet disinfection process is results in cleaner effluent than chlorination which contains residual chlorine that can damage the environment. Tertiary treatment is also called as disinfection treatment which is an essential step because it protects humans health.