PHOTOVOLTAIC SYSTEM BASED SEWAGE TREATMENT PLANT
FIELD OF THE INVENTION
The present invention generally relates to sewage (domestic waster water) treatment plant, particularly to sewage treatment plant powered by renewable energy. More particularly, the present invention relates to a low cost system of integrating sewage treatment plant with photovoltaic system resulting in less carbon foot print. Further, the system is configured and integrated to match performances that include load generation cycle, power generation and treatment cycle.
BACKGROUND ART
In general, sewage treatment is the process of removing contaminants from domestic wastewater, primarily from household sewage and produce environmentally safe treated effluent. The sewage treatment process includes physical, chemical and biological processes to remove the contaminants. A by-product of sewage treatment is usually a semi-solid waste or slurry, called sewage sludge that has to undergo further treatment before being suitable for disposal or land application. Sewage treatment may be of de-centralized system or centralized system. Aerobic sludge digestion is a biological process that takes place in the presence of oxygen. With oxygen, the bacteria present in the activated sludge consume organic matter and converts it into carbon dioxide. Sewage treatment plants powered by various energy resources do exist in prior arts.

In most of the rural areas, sewage digesters used is simple in procedure with direct discharge to the environment causing great harm. Further, rural areas which lacks power supply utilizes solar powered sewage treatment plant. But the problem associated it with is during bad weather, it is difficult to treat the sewage. Another problem that is associated is lack of backup power storage that is required for sewage treatment during non solar hours.
Further, the typical problems associated in adopting solar system for aerobic digestion based sewage treatment plant is matching the load generation cycle, power generation and the treatment cycle.
Accordingly, there exists a need for cost effective, environment friendly solar powered sewage treatment plant that optimally matches the performance of photovoltaic system with sewage treatment plant requirements. Further, there is need for a solar powered sewage treatment plant with less carbon foot print and which can be implemented in remote places where electrification is not available or grid availability is difficult.
SUMMARY OF THE INVENTION
One or more problems present of the prior art may be overcome by various embodiments of the present invention.

Accordingly it is the primary object of the present invention to provide sewage treatment plant powered by renewable energy.
Another object of the present invention is to provide low cost system of integrating sewage treatment plant with photovoltaic system resulting in less carbon foot print.
Yet another object of the present invention is to match the performance of photovoltaic system with sewage treatment plant requirements that include load generation cycle, power generation and treatment cycle.
It is another object of the present invention, wherein the photovoltaic system integrates with either net energy metering or battery system,for providing extended hour of operation, where required.
It is another object of the present invention to provide de-centralization of photovoltaic system based sewage treatment.
It is another object of the present invention, wherein shape and configuration of the photovoltaic system can be customized.
The photovoltaic system based sewage treatment plant comprising of all or any of:

solar modules;
solar inverter;
collection-cum-aeration tank;
air blowers;
settling tank;
one or more filters;
net energy meter; and
battery. It is another object of the present invention, wherein the collection-cum-aeration tank provides a maximum interface between the atmosphere and the water to ensure minimal oxygen supply to sewage water even during the non-solar hours.
It is another object of the present invention, wherein excess power generated by the photovoltaic system is pumped to grid and drawn back from the grid during non solar hours for sewage treatment process.
It is another object of the present invention, wherein the excess power generated by the photovoltaic system is stored in the battery for providing extended hour of operation, during non solar hours.

Working:
The solar modules which generates power using solar rays is fed to the solar inverter which in turn convert solar power to AC power to drive motors. The solar inverter includes but not limited to off-grid inverter, grid-interactive inverter, uninterrupted power supply. The collection-cum-aeration tank aerates the raw sewage effluent collected and provides retention time. The collection-cum-aeration tank keeps the peak in flow of effluent, particularly with optimal depth to provide a maximum interface between the atmosphere and the water to ensure minimal oxygen supply to sewage water even during the non-solar hours. Using aeration the Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) and foul smell due to free ammonia and hydrogen sulphide is addressed before discharging. The air blowers which supply air to the raw sewage effluent to meet the oxygen demands may be of AC or DC driven. The aerated water is then transferred to the settling tank, where most of digested biomass and suspended particles is settled-down as sludge. The settling tank is configured such that most of the treatment is completed during solar hours. The treated water is fed through one or more filters to separate the residual sludge and clear overflow water is ready to use. The filters include but not limited to media filter and pressure sand filter. Based on the requirement the clear treated water is chlorinated or ozonized for disinfection. The settled sludge is transferred to sludge drying bed at regular intervals. The energy meter measures the net energy between the export and import energy from and to the system.

The photovoltaic system is optimized by utilization of energy efficient devices like variable frequency drives or DC drives for blowers and pumps. The system further includes combination of micro-filtration, ultra-filtration, nano-filtration and reverse osmosis to make the water potable for drinking. The excess power generated by the photovoltaic system is drawn back from the grid during non solar hours for sewage treatment process. Alternatively or also, the excess power generated by the photovoltaic system is stored in the battery for providing extended hour of operation, during non solar hours. It should be noted that the dimension and configuration of the components used in the photovoltaic system may vary based on the requirements.
BRIEF DESCRITPION OF DRAWINGS:
Figure 1: illustrates photovoltaic based sewage treatment plant with grid interactive inverter according to the present invention.
Figure 2: illustrates photovoltaic based sewage treatment plant with stand alone inverter according to the present invention.