How SaveNadi checks the water, how it decides that something is wrong, and what it cannot tell you. In the app, point at or tap the next to a word to see what it means.
SaveNadi watches the water in Maharashtra's rivers and coast, raises an alarm when pollution crosses a limit, helps officers find the source, and keeps a record of what was done.
Sensor boxes are placed in rivers, creeks and the sea, and where industrial areas release their waste water. No box is inside a factory. Each box tests the water every 30 seconds.
About every 2 minutes, each box sends its readings over the mobile network, radio or satellite.
SaveNadi compares every reading with the Central Pollution Control Board (CPCB) limit for that kind of place.
If a limit is crossed, a case opens for Maharashtra Pollution Control Board (MPCB) officers, with the reading, the place and the time.
It compares the dirty water with the known waste of nearby registered factories and suggests which one to check first. This is only a suggestion, called an AI (artificial intelligence) lead.
The officer reviews the suggestion, visits the place and takes a water sample for testing in a government-approved lab.
For example, a notice or a direction to the factory. The decision is recorded with the officer's name and the time.
The sensors show whether the water gets better after the action. If the same limit is crossed again within 7 days, the case opens again.
Every step is saved in a log where any later change can be spotted. Anyone can see the water quality on this website.
SaveNadi has its own sensors at 23 places in western Maharashtra: where industrial areas release waste water into a river (called outfalls), in rivers, and on the coast. No sensor is inside a factory. Factories also have their own meters, called the Online Continuous Effluent Monitoring System (OCEMS); SaveNadi shows that data separately.
Right now this is a trial (pilot). The sensor readings are simulated: made by a computer to test the system. Every record says whether it is real or simulated, and a yellow strip at the top of the page says so.
A site is reporting if it sent at least one reading in the last 24 hours. We also show how recent the last reading is: live (less than 15 minutes old), delayed (less than 6 hours), stale (less than 7 days) or no data. Stale readings are never shown in warning colours.
All the probes sit together in one sensor box at the site. The box tests the water every 30 seconds and sends the readings about every 2 minutes, over the mobile network, radio or satellite. In this pilot the readings are simulated; this is how the box is designed to work.
A sensor reading is a first check only. Before any legal action, a water sample must be tested in a government-approved lab.
Scale of 0 to 14
How acidic or alkaline the water is. 7 is neutral; lower is acidic, higher is alkaline.
Measured in milligrams per litre (mg/L)
The oxygen dissolved in the water, which fish and other river life breathe.
Measured in milligrams per litre (mg/L)
How much oxygen bacteria use up to break down organic waste, such as sewage and food, sugar or dairy waste.
Measured in milligrams per litre (mg/L)
How much oxygen is needed to break down all the waste in the water, including chemicals that bacteria cannot break down.
Measured in nephelometric turbidity units (NTU)
How cloudy or muddy the water is.
Measured in microsiemens per centimetre (µS/cm)
How easily the water carries electricity. This shows how much dissolved salt and minerals it holds.
Measured in milligrams per litre (mg/L)
Ammonia in the water, mostly from sewage, fertiliser and food-processing waste.
Measured in milligrams per litre (mg/L)
Chromium metal in the water, from leather tanning, electroplating and dye units. The sensor measures all forms of chromium together.
Measured in milligrams per litre (mg/L)
A poisonous element, from some chemical, pesticide and glass industries.
Measured in milligrams per litre (mg/L)
A toxic metal, from some chemical factories (such as those making caustic soda), medicine factories and electronic-waste units.
Measured in milligrams per litre (mg/L)
A toxic metal, from battery, paint, metal and electronics units.
Measured in °C
How warm the water is.
Every reading is checked against one limit, and the limit is shown next to the reading. The limit depends on the place.
Where industrial areas release waste water: the limits that the Central Pollution Control Board (CPCB) sets for waste water going into rivers. For example: pH 5.5 to 9.0, Biochemical Oxygen Demand (BOD) 30 milligrams per litre (mg/L), Chemical Oxygen Demand (COD) 250 mg/L, total chromium 2.0 mg/L. Oxygen and conductivity have no such limit, so there they are shown for information only.
In rivers, creeks, lakes and the sea: CPCB's limits for river water, where they exist: pH 6.5 to 8.5, dissolved oxygen at least 5 mg/L, and conductivity up to 2,250 microsiemens per centimetre (µS/cm). There is no river limit for COD, BOD or metals, so the waste-water limit is used as a warning line, called a screening threshold. Total chromium uses 0.1 mg/L.
Ammonia at 5 mg/L, turbidity at 10 nephelometric turbidity units (NTU) and temperature at 40 °C use warning lines set for this pilot, everywhere. The CPCB waste-water limit for ammonia is 50 mg/L.
How serious a case is depends on the limit for that place. Chromium always means total chromium (all forms together). It is never compared with the stricter limit for its most harmful form, hexavalent chromium, because the sensor cannot tell the forms apart.
A sensor reading tells officers where to look. It is not legal proof. For legal action, a water sample must be collected in the proper way and tested in a government-approved lab.
Limit crossed: the reading is outside its limit.
Unusual reading: the reading is much higher (or, for oxygen, much lower) than this sensor normally shows, and it is close to the limit. It is marked “unusual” even if the limit is not crossed yet. (For experts: more than 4 robust standard deviations from the sensor's recent median.)
When a limit is crossed, the computer compares the dirty water with the known waste-water pattern of each registered factory on the same river. Nearer factories count more. It gives a match score: close (0.8 or more), partial (0.5 to 0.8) or weak (0.25 to 0.5). Below 0.25 no factory is suggested. The score is not a chance or probability. Factories that are not registered, and city sewage, are not included, and the method has not yet been tested against cases confirmed by officers.
An AI (artificial intelligence) lead only says where to look first. It does not prove that a factory is at fault. An officer must review it before any action, and no enforcement decision can be recorded until then.
Sometimes the app draws a straight line through the last 40 readings, to show where the reading may go in the next 6 hours. It is only a rough guess, not a forecast, and it is greyed out once those 6 hours have passed.
Under Central Pollution Control Board (CPCB) directions of 2014, 17 categories of highly polluting industries, and common effluent treatment plants, must fit their own meters, called Online Continuous Effluent Monitoring Systems (OCEMS), and send the data to the Maharashtra Pollution Control Board (MPCB) and CPCB. SaveNadi shows this separately and checks whether the factory's reading matched SaveNadi's own sensor, was different, or was missing. If less than half of the factories sent data that day, the check is marked “not available”, so no factory is blamed for a system breakdown. Why a reading differs is for an officer to find out, not the computer.
SaveNadi also checks each factory meter's own readings every 15 minutes. It raises an alert when the meter sends nothing for 1 hour or more (for 24 hours or more, a violation under the proposed rule), when a reading is above the factory's consent limit, when the same value repeats for 3 hours, when a value cannot be real (such as pH above 14), when a reading suddenly falls to a fifth or less of its usual level for an hour or more, when fewer than 85% of a day's readings arrive, and when the meter reads lower than SaveNadi's own river sensor. These rules and timings are proposals for the Maharashtra Pollution Control Board (MPCB) to agree. Each alert is a signal for an officer to check, not a finding against the factory. In this pilot the factory meter readings are simulated.
The Brief (the daily summary for officers) is written by fixed rules that work the same way every time (rule set 1.0). It is not written by an artificial intelligence (AI) chatbot. Every sentence is marked Measured (from the sensors), AI lead (a suggestion) or Recommended (a next step), and links to the records behind it. Anyone can report a mistake in a Brief, and every report is recorded.
Every alert, evidence file and officer action is saved in a chain of records. Each record carries a digital fingerprint that includes the fingerprint of the record before it. If anyone changes an old record, every fingerprint after it stops matching, so the change is caught. This does not stop changes, but it makes them visible.
When the system moved to its present servers (Cloudflare), the chain was sealed again with the same content, and that step is itself recorded in the chain.
Automatic steps such as closing a valve are only simulated in this pilot; they never control real equipment. A factory named as an AI (artificial intelligence) lead can ask to see the data and give its reply through the operator.