RASHTRIYA CHEMICALS AND FERTILIZERS

LIMITED

Internship-Report
Study of electrical systems in Sewage Treatment Plant
In-plant Training 04.06.2024 - 03.07.2024
Report Submitted by
Neena Chauhan
Department of Electrical Engineering,
FR. C Rodrigues Institute of technology
 Acknowledgement
It gives me immense pleasure to represent the report on manufacturing of
Ammonia- 1 studied during the internship at Rashtriya Chemicals and Fertilizers,
Mumbai.

I want to express my sincere appreciation for the invaluable experience gained

during my internship for the guidance, mentorship, and unwavering support,
which significantly enhanced my understanding of the plant operations.

I extend my thanks to the entire RCF Ltd. team for fostering a collaborative and
professional environment. Engaging with various departments broadened my
perspective on the industry, and the exposure to different facets of plant
operations was instrumental in my professional growth. I extend my special
thanks to Umesh Tembhare sir, DGM (HRD) for their invaluable guidance and
supervision throughout the training process.

I also appreciate the patience and dedication shown by my colleagues in

addressing my queries, contributing to a positive learning environment. The skills
and knowledge gained during my internship, along with the professionalism
instilled, will undoubtedly shape my future endeavors in the industry.

Thank you, RCF Ltd., for providing me with this enriching opportunity. I am
excited to apply the insights gained in my future professional pursuits.
 SAFETY

Q. What is Safety?

A. The freedom from those conditions that can cause death, injury or

illness, da mage to/loss of equipment or property, or damage to the

environment.

Q. What are unsafe conditions and unsafe actions?

A. Unsafe Act can be defined as any activity by workers which are
not as per the prescribed safety standard or practice and which can
cause or likely to cause accidents or risk for self or others at
workplace, damage equipment’s and bring losses in terms of
reputations and revenue to employer. Such human acts can be due
to callous attitude of workers or lack of awareness on safety
measures or not following safe work practices.
In general, unsafe activities can lead to unsafe conditions.
Any condition or situation (electrical, chemical, biological, physical,
mechanical and environmental) which increases the risks and dangers
of accidents can be called as unsafe conditions.

Let us understand this concept through an example:

Let us assume a road accident which happened in a city during the

day time.

The accident would have happened due to unsafe driving, unsafe road
condition, or improper vehicle condition. There can also be some
natural reasons behind such road accidents but they are too little to
compare with accidents caused by human errors and unsafe roads.

So,

It is the unsafe human activities that are behind majority of accidents

which are happening on roads, houses and at workplaces.

In the workplace accidents, unsafe conditions can be created due to

faulty equipment’s, exposure to dangerous conditions without
protection, not following basic safety procedures and existence of
unhealthy conditions.

Q. What is Risk? How to eliminate and substitute it?

A. Any action or activity that leads to loss of any type can be termed

as risk.

• Elimination
• The preferred method for risk control, elimination involves
making a different decision or taking steps to ensure the risk cannot
occur.

• Substitution

When eliminating the hazard is not possible, substitution involves

replacing it with a safer alternative. For example, replacing noisy
equipment with a quieter option or a toxic chemical with a less
dangerous version.

• Risk avoidance

This strategy involves taking measures to prevent the risk from

occurring. For example, not making an investment or starting a
product line.

• Risk sharing

This involves partnering with others to share responsibility for risky

activities.

• Risk isolation

This involves isolating the risk from the person who may experience
it, or limiting access to the risk factor to only authorized personnel.

• Risk acceptance

This involves deliberately choosing to bear the impact of a potential

risk. After making a substitution, it's important to conduct a new risk
assessment to identify any new risks created by the substitution
process.

Q. What is the difference between human error and negligence?

A. Human error is when someone makes a mistake unintentionally,

even though they were trying to do the right thing. Negligence is

when someone fails to take proper care or ignores their

responsibilities, often leading to problems that could have been

avoided.

In the workplace, human errors can have serious consequences,

such as injuries or fatalities. Someone who suffers a loss due to

another person's negligence may be able to sue for damages.

Q. What are Mock drills?

A. A mock drill is a practice exercise that simulates an emergency to

prepare people for how to respond in real life.

The types of mock drills in power plants can be categorized as

follows:

• In-Plant Mock Drills Conducted within a single plant to train

staff on handling internal emergencies like equipment failure, fire, or
system malfunction.

• Example: A fire drill in the boiler room.

• Inter-Plant Mock Drills Conducted between multiple plants
within the same organization to coordinate responses to emergencies
that may affect or require collaboration among them.

• Example: Simulating a power grid issue that impacts multiple

plants.

• Outer-Plant Mock Drills

• Involve external agencies such as local fire departments, police,

and disaster management teams to address large-scale emergencies.

Example: A drill for handling a chemical spill that impacts the

surrounding community.

Each type helps improve preparedness at different levels of

operation and coordination.

Q. What are Windsocks?

A. Windsock is a conical-shaped tube that indicates wind speed and

direction:

• Shape

A windsock is a tapered, open-ended cloth tube that looks like a giant

sock.

• Purpose

Windsocks are used to indicate wind speed and direction, and are
often found at airports, chemical plants, and highways.
• How it works

The windsock's angle relative to the mounting pole indicates wind

speed. In low winds, the windsock droops, and in high winds, it flies
horizontally.

• Lighting

Many windsocks are lit at night with floodlights or a light mounted on

the pole.
 STP PLANT

Background of the project

When Rashtriya Chemicals & Fertilizers Ltd., (RCF) Chembur

(formerly known as Fertilizer Corporation of India, Trombay Unit) was
established about four decades ago, the site for the plant was choosen
such that it was located in an industrial area away from residential and
commercial zones of the city of Mumbai (Bombay).

This industrial zone was developed on a marshy land close to creek.

Consequently, the ground water resources in the area are unfit for most
of the usage unless the water is treated at high cost due to nature of
water. Later, as the population in the city grew and the city expanded,
the fertiliser plant found itself in the middle of residential, commercial
and industrial area. The management of RCF have taken several steps
over the years to mitigate the problems due to air, water and solid waste
pollution and have endeavored to keep all the parameters within the
limits specified by state agencies from time to time.

The water requirement of R. C. F. plant was met by Municipal

Corporation Water Distribution Network available in the area, which
supplies high quality drinking water. Since this water is better used by
ever growing population of the area, the enlightened and foresighted
management of RCF in cooperation with civic authorities decided to
implement a sewage treatment project, wherein, they could procure
sewage from Municipal Corporation Network and treat the same to
their required standards. The management of RCF saw two major
benefits in the implementation of this project.

 Project will help in safely disposing off 950 cum/hr (5 MGD)

of sewage and
 Project will save consumption of above 800 cum/hr (4.2 MGD)
of potable water from the civic body.
Design Input

SR PARAMETER VALUE
.
N
RAW AFTER AFTER
O
SEWAGE TERTIARY REMOVAL
TREATMENT OF
DISSOLVED
SOLIDS
1. pH 6.6-7.2 7.00 7.00

2. Total Suspended Solids, ppm 250-300 < 5 < 5

3. Total Dissolved Solids, ppm 600-650 600-650 80-100

4. Total Hardness, ppm 175-200 175-200 40-60

5. Chemical Oxygen Demand(COD), 400-450 15-20 < 5

ppm
 6. Biological Oxygen Demand (BOD), 300-350 < 5 < 2
ppm

7. Chlorides, ppm 150-180 150-180 15-20

8. Sulphates, ppm 40-60 40-60 15-20

9. Ammonia Nitrogen, ppm 20-30 < 5 < 1

10. Nitrate Nitrogen, ppm 15-20 < 15 < 1

11. Oil & Grease, ppm 20-30 < 1 < 1

Major treatment steps include:--

a) Screening
b) Grit Separation
c) Extended Aeration
d) Clarification and Oil Removal
e) High rate clarification
f) Sand Filtration
g) Chlorination
h) Coagulation and Pressure Filtration
i) Micron Cartridge Filtration
j) De chlorination
k) Acid and Anti-scalant dosing
l) Reverse Osmosis
m) Degasser.
1.

2.
 SOLAR FEEDER

In addition to the STPs, RCF has invested in renewable energy by

installing a 2 megawatt peak (MWp) ground-mounted solar power
generation plant at the Trombay unit, along with rooftop photovoltaic
(PV) solar power generating facilities totaling 2.12 MWp across its
Trombay and Thal units. These solar installations collectively
generate over 5,000 megawatt-hours (MWh) of green power annually,
reducing reliance on fossil fuels and contributing to lower greenhouse
gas emissions.
Plant info:-

Capacity: 2MW

Year of establishment:- January 2016

No. of modules:- 6900 modules

1 table:- 20 modules

No of tables:- 345

One module generate 305 watt

The plant is ground mounted.

Grid inverter were used earlier to convert AC to DC but now they are
shifting towards the string inverter.

What is grid inverter?

A grid inverter is an electrical device used in renewable energy

systems (such as solar or wind power) to convert the direct current
(DC) produced by energy sources into alternating current (AC), which
is compatible with the electrical grid. It plays a critical role in
ensuring the generated power can be efficiently fed into the grid or
used by standard appliances.

What is String inverter?

A string inverter is a type of grid-tied inverter commonly used in solar

photovoltaic (PV) systems. It is designed to convert the direct current
(DC) electricity produced by a series (or "string") of solar panels into
alternating current (AC) electricity, which can be used by appliances
or fed into the electrical grid.
Key advantages over conventional grid inverter

Key Features of a String Inverter:

1. String Connection: Solar panels are connected in series to form a

"string," and the inverter converts the combined DC power from the
string into AC power.

2. Centralized Inversion: All the DC power from the panels in the

string is processed by a single inverter.

3. High Efficiency: String inverters typically offer high efficiency in

converting energy from DC to AC.

4. Cost-Effectiveness: They are more affordable compared to other

types, such as microinverters, making them popular for medium to
large-scale installations.

Capacity of grid inverter:- 500KW

Capacity of string inverter:- 125KW

No of grid inverter:- 4

No. of grid inverter:- 16

No. of tables connected to one grid inverter:- 88

No. of tables connected to one string inverter:- 22

String inverters can be susceptible to shading issues as the

performance of the entire string is affected if one or more panels are
shaded. String inverters are easy to maintain because there is only one
inverter to troubleshoot and repair.
 Fig: difference of current in grid inverter and string inverter

(grid inverter being centralised shows less current while string

inverter shows more current as it reads individual panels)

String inverters are not affected by the difference between PV string

and shadow. String inverter optimize the voltage to get maximum
current during less irradiance, shadow, rain etc.

String inverters can generate the power even in bad weather.

String inverters are small in size and light weight, they are easy to
install also they remove the unnecessary transformers and switchgears
which are required in grid inverter system which makes it compact
and requires less maintenance and man power. It can be monitored
through application which can be operated through mobile phone
also.
Challenges during conversion from grid inverters to string inverters: -

1. Design and Installation Challenges

System Design Complexity: Ensuring proper alignment between solar

panels and inverters for maximum efficiency.

Cable Management: Managing the DC cabling and ensuring proper

connections can be cumbersome in larger installations.

Space Requirements: Finding suitable locations for installing string

inverters while considering ventilation and accessibility.

2. Environmental Factors

Temperature Sensitivity: String inverters can overheat in high-

temperature environments if ventilation is inadequate.

Weather Protection: Ensuring the inverters are adequately protected

against rain, dust, and other environmental elements.

Shading Impact: Shading on even a single solar panel can reduce the
overall performance of the string inverter system.

3. Electrical Challenges

Voltage Drop: Managing voltage drop over long distances, which can
affect performance.

Grid Compatibility: Ensuring the inverter's settings match the grid

requirements in terms of frequency and voltage.

Earthing and Protection: Proper grounding and surge protection to

ensure safety and prevent damage.
4. Technical and Operational Issues

Monitoring and Communication: Ensuring proper integration of

monitoring systems to track inverter performance.

Fault Diagnosis: Identifying and resolving faults in a string inverter

setup can be time-consuming, especially in complex systems.

Firmware Updates: Regular updates may be required to maintain

compatibility and efficiency.

5. Regulatory and Compliance Issues

Permits and Standards: Adhering to local electrical codes and

standards during setup.

Grid Connection Approval: Obtaining approval from the utility

company for connecting the inverter to the grid.

6. Cost Implications

Initial Costs: High initial investment in quality inverters and

accessories.

Maintenance Costs: Regular maintenance to ensure long-term

reliability and performance.

Disadvantages of string inverters

1.Single point of failure

If the inverter breaks down, the whole solar array will be inoperable.
This could be a significant loss of electricity production.
2.Expandability

Unless you buy an oversized string inverter, expandability in the

future is restricted as once installed for a certain rating, the rating of
the inverter could not be altered. In this case you would need to buy
an additional inverter.
 STP-2 PLANT

The main difference between STP 1 and STP 2 is membrane bio

reactor.

What is membrane bio reactor?

A Membrane Bioreactor (MBR) is an advanced wastewater treatment

technology that combines biological treatment and membrane
filtration processes in a single system. It is widely used for treating
municipal and industrial wastewater to produce high-quality treated
water suitable for reuse or discharge.

Key Components:

1. Bioreactor:

Contains microorganisms that biologically degrade organic matter,

nutrients, and other contaminants in the wastewater.

Operates under aerobic (oxygen present) or anaerobic (no oxygen)

conditions, depending on the treatment objectives.

2. Membrane Filtration:

Utilizes membranes (microfiltration or ultrafiltration) to physically

separate solids, bacteria, and other impurities from the treated water.

The membranes have pore sizes typically ranging from 0.01 to 0.1
microns.

Working Process:

1. Biological Treatment:
Wastewater enters the bioreactor, where microorganisms break down
organic pollutants through metabolic processes.

2. Membrane Separation:

Treated water passes through the membranes, while suspended solids,

microorganisms, and other contaminants are retained.

3. Sludge Handling:

Retained solids are either recycled back into the bioreactor or

removed periodically as waste sludge.

Advantages:

High-Quality Effluent: Produces treated water with very low levels of

suspended solids, turbidity, and pathogens.

Compact Design: Requires less space compared to conventional

treatment methods.

Reduced Sludge Production: More efficient biological degradation

reduces waste sludge volume.

Flexibility: Can handle varying wastewater loads and qualities.

Applications:

Municipal wastewater treatment.

Industrial wastewater treatment (e.g., food processing,

pharmaceuticals).
Reuse applications like irrigation, industrial processes, and cooling
water.

Limitations:High Cost: Membranes and operational costs are

relatively high.

Maintenance: Membranes require regular cleaning and may need

replacement due to fouling.

Energy Consumption: Pumping water through membranes can

consume significant energy.

MBR technology is increasingly adopted due to its ability to meet

stringent wastewater discharge and reuse standards.

Details of stp 2 plant: -

Inlet chamber- to reduce velocity

Screen 6mm- size separation

Grit removal- to separate solid liquid

In grit removal mainly silica is removed.

2mm bar screen

Anoxic splitter box-uniformly distribute and add bacteria

Aerobic tank- add oxygen through blowers

Post anoxic- no oxygen

Membrane bioreactor(MBR)- vaccum filter

Core size- 0.04 micro meter

RO- 0.001 micro meter

Intermediate storage tank- chlorination

Min. chlorine- 2ppm

Reverse osmosis

Initial conductivity- 355

Final conductivity- 50

Sewage-22.75 MLD

Total sewage of both STP- 45 MLD

STP- 15 MLD

Total production-30 MLD

Efficiency - 66.66%

1 MLD- 1000m cube

RCF- 14MLD

BPCL- 8MLD

RO- permeate and reject

Inlet flow- 140.3

Permeate- 105

Reject – 35

Efficiency - 75%

STP-1 RO
Inlet- 187

Outlet- 107

Efficiency- 57%
 EFFLUENT TREATMENT PLANT
History of Effluent treatment in RCF
➢ In 1965 Trombay unit commissioned .
➢ Manufacture of Nitrogen & Phosphatic fertilizers by
using unique Nitro-Phosphatic route not followed
anywhere in the country till 1991.
➢ Hence conventional type of Effluent Treatment system
was not suitable at that time to meet MINAS.
➢ ETP started in the year 1978 with the treatment of
Phosphates and Fluorides to meet standards prevalent at
that time.
➢ The satisfactory process route was developed for
treatment of Nitrogen in 1990 with the advice of MPCB,
In December 1992 new facilities were added to achieve
the standards quoted by MPCB & MINAS.
Characteristics of effluents
Treatment Stages
◼ Sedimentation
◼ Removal of Phosphate & Fluoride
◼ Ammonia Stripping
◼ Biological Nitrification
◼ Biological De-nitrification
◼ Final Polishing & Neutralization
◼ Sludge collection & disposal

MPCB Standards for Treated Water

Parameter MPCB standard

pH 6.5-8.0
Dissolved Phosphate as P Not to exceed 5 Mg/l
Dissolved Flouride Not to exceed 10 mg/l
Amm. Nitrogen Not to exceed 75 mg/l
Nitrate Nitrogen Not to exceed 20 mg/l
COD Not to exceed 250 mg/l
BOD Not to exceed 100 mg/l
Suspended solids Not to exceed 100 mg/l
Free Ammonical Nitrogen Not to exceed 100 mg/l
Total Kjeldhal Nitrogan Not to exceed 150 mg/l
Oil Not to exceed 10 mg/l
Arsenic Not to exceed 0.2 mg/l
Vanadium Not to exceed 0.2 mg/l
Cyanide Not to exceed 0.2 mg/l
By products

Sr.No. Name of Product Specification General Uses

properties
1 Chemical Sludge P2O5 = 20- amorphous Used as raw
30% material in
CaO = 50 % Suphala Plant
for recovering
Phosphate in
it. Earlier it
was sold to
parties which
were using it
as cattle feed.
2 Biological sludge Contains 50% Wet ,slushy, As a manure
organic and 50 difficult to dry for
% inorganic horticulture
mass. use
 Conclusion
In conclusion, my time working at the STP/ETP plant in the chemical
industry has been an enriching and invaluable experience. Throughout
this period, I have gained profound insights into the intricate
processes and operations involved in the sewage and effluent
treatment of water. The combination of theoretical knowledge and
hands-on experience has deepened my understanding of the chemical
industry, particularly in the context of sewage treatment.
One of the most significant takeaways from this experience is the
paramount importance of safety and adherence to stringent protocols
within the plant. The meticulous attention to detail, the rigorous
implementation of safety measures, and the commitment to
environmental sustainability have underscored the industry's
dedication to responsible practices.
The challenges encountered whether in troubleshooting equipment
issues or ensuring optimal process efficiency, have honed my
problem-solving skills and heightened my adaptability to the dynamic
nature of industrial operations. The collaborative nature of the work
environment has also emphasized the significance of effective
communication and teamwork in achieving operational excellence.
I extend my sincere gratitude to the dedicated team at the STP plant
for their guidance and support throughout this experience. Their
expertise and willingness to share knowledge have been instrumental
in my professional development.