Lecturer: Dr. Mahmoud Nasr

Sanitary Engineering Department Faculty of Engineering Alexandria University

Zero Liquid Discharge Systems

8th November, 2014

Fertilizer ZLD

Fertilizers

-Fertilizer is a material of natural or synthetic added to the

soil to supply one or more plant nutrients.

-Examples of primary plant nutrients are nitrogen or

phosphorus

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Nitrogen fertilizer

More than 80% of the fertilizers used in Egypt are made up of nitrogenous

fertilizers, particularly urea

Nitrogen fertilizer ZLD

Ammoniacal (NH3-N)

Example:

Ammonium Sulphate

(NH4)2SO4

Ammonium chloride

NH4Cl

Anhydrous ammonia

NH3

Nitrate (NO3−)

Example:

Sodium Nitrate

NaNO3

Calcium Nitrate

Ca(NO3)2

Potassium Nitrate

KNO3

(NH3-N) and (NO3−)

Example:

Ammonium Nitrate

(NH4)(NO3)

Calcium Ammonium Nitrate

CAN

Ammonium Sulphate Nitrate

ASN

Amide fertilizer

Example:

Urea

CH4N2O

Calcium

Cyanamide

CaCN2

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Nitrogen fertilizer

Ammoniacal (NH3-N) - Contain the nutrient nitrogen in the form of ammonium or ammonia. -Except rice, all crops absorb nitrogen in nitrate form. -Resistant to leaching loss, as the ammonium ions get readily absorbed on the colloidal complex of the soil.

Nitrate (NO3−)

-Contain the nitrogen in the form of NO3. -Easily lost by leaching because of the greater mobility of nitrate ions in the soil. -Continuous use of these fertilizers may reduce the soil acidity as these nitrogenous fertilizers are basic in their residual effect on soils.

(NH3-N) and (NO3−)

-Contain nitrogen in both ammonium and nitrate forms. -The nitrates are useful for rapid utilization by crops and the Ammoniacal is gradually available

Amide fertilizer -Are readily soluble in water and easily decomposable in the soil. -Urea is the most concentrated solid nitrogenous fertilizer, containing 46 % nitrogen.

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Nitrogen gas N2

Nitrogen fixation

Organic Nitrogen

Ammonification

Ammonium NH4

+

Denitrification

Nitrite & Nitrate NO2

- & NO3-

Nitrification

Nitrogen Cycle

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Fertilizer

Cattle manure Plants

NH4+ NO2

- NO3

-

NO2-

Denitrification

N2 Fixation (Protein)

Consumption

Leaching

ON

Dec

ay

Nitrogen Cycle

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Sewage

Ammonia NH3

NO2- NO3

- NO2-

N2

Industrial fixation

Denitrification Nitrification

Uptake

Uptake

Nitrogen Fertilizer ZLD system

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Influent

Digester

Effluent with Ammonia

Stripping

Clean effluent

Hot air Nitrogen rich

fertilizer product

Nitrogen fertilizer ZLD system

-Nitrogen fertilizers containing nitrogen as a base element, which is expressed by N2 %.

-Ammonia is considered the main raw material of nitrogenous fertilizers manufacturer.

Ammonia

gas

Reuse

Recycle

- Phosphatic fertilizers containing phosphorous as a base element, which is

expressed by P2O5 %.

- Phosphate rock is considered the main raw material for the production of

phosphate type fertilizers.

- Phosphate fertilizers industry is considered one of the most polluting

industries in Egypt.

- Phosphate fertilizers include single superphosphate and triple

superphosphate. The single superphosphate is a mixture of monocalcium

phosphate and gypsum (available P2O5 almost 16- 22 %), while triple-

superphosphate is composed mainly of monocalcium phosphate (available

P2O5) almost 46 %).

Phosphate fertilizer ZLD

Phosphate fertilizer

Phosphatic fertilizers containing phosphorous as a base element, which is

expressed by P2O5 %.

Phosphate rock is considered the main raw material for the production of

phosphate type fertilizers.

Phosphate fertilizer ZLD

Super phosphate Ca(H2PO4)2

- The most important phosphatic fertilizer in use.

- Contains 16 % P2O5 in available form. - A grey ash like powder with good

keeping or storage qualities. - Hardly moves in the soil and hence

they are placed in the, root zone.

Triple super phosphate - Contains 46 % P2O5. - Suitable for all crops and all soils. - In acid soils, it should be used in

conjunction with organic manure. - Applied before or at sowing or

transplanting.

Fertilizer

Cattle Plants

Phosphate fertilizer

Organic phosphate

Up

take

Inorganic phosphate

Mineralization

Consumption

Death

Leaching & surface runoff

Phosphorus Cycle

Fixed phosphate

Anaerobic Aerobic BOD

Substrate Clarifier

Anaerobic Aerobic

Sludge PAO Fertilizer

Reuse

Biological Phosphorus Removal

Recycle

PO4

PO4

Chemical Phosphorus Removal

- Phosphates are precipitated as calcium phosphate in the second stage

neutralization and clarification at pH range of 8 - 9.

- This demands a very fine, effective and reliable control of lime injection.

Pre-treatment for ZLD

WWTP

Process

Industry, Agric. Treatment

Influent

Effluent

Treated

Recycle

Reuse

Phosphate Fertilizer Manufacturing produce

1) Sulphuric acid

2) Phosphoric acid

3) Single superphosphate (SSP) and Triple superphosphate (TSP)

4) Compound Fertilizers (NPK)

1) Sulfuric Acid

- Sulfuric acid (H2SO4) is used in the phosphate fertilizer industry for the

production of phosphoric acid.

- Sulfuric acid is manufactured mainly from sulfur dioxide (SO2), produced

through the combustion of elemental sulfur.

- The exothermic oxidation of sulfur dioxide over several layers of a

suitable catalyst (e.g. vanadium pentoxide) to produce sulfur trioxide

(SO3) is the most common process in sulfuric acid manufacturing plants

- Sulfuric acid is obtained from the absorption of SO3 and water into

H2SO4 (with a concentration of at least 98 %) in absorbers installed after

multiple catalyst layers.

2) Phosphoric Acid

-Phosphoric acid (H3PO4) is primarily used in the manufacture of

phosphate salts (e.g. for fertilizers and animal feed supplements).

-Two different processes can be used in the manufacture of phosphoric

acid.

-In the first process, known as the thermal process, elemental

phosphorous is produced from phosphate rock, coke, and silica in an

electrical resistance furnace and is then oxidized and hydrated to form the

acid.

-The second type of process, known as the wet process, involves digesting

phosphate rocks with an acid (e.g. sulfuric, nitric or hydrochloric acid).

3) Phosphate Fertilizers (SSP / TSP)

-Phosphate fertilizers are produced by adding acid to ground or pulverized

phosphate rock.

-If sulfuric acid is used, single or normal, superphosphate (SSP) is

produced, with a phosphorus content of 16–21 % as phosphorous

pentoxide (P2O5).

-If phosphoric acid is used to acidulate the phosphate rock, triple

superphosphate (TSP) is produced with a phosphorus content of 43–48 %

as P2O5.

4) Compound Fertilizers (NPK)

-Compound fertilizers are a large group of products, varying based on the

particular nitrogen / phosphorus / potassium (N/P/K) ratios.

- This can be achieved by using two different routes, namely production

by the nitrophosphate route, and production by the mixed acid route.

-National Fertilizer Public Company Ltd of Thailand (NFC) installed modern

NPK fertilizer plant including a phosphoric acid manufacturing unit within

the complex.

Compound Fertilizers (NPK)

-Ammonium phosphates are produced by mixing phosphoric acid and

anhydrous ammonia in a reactor to produce a slurry. This is the mixed-

acid route for producing NPK fertilizers; potassium and other salts are

added during the process.

-Nitrophosphate fertilizer is made by digesting phosphate rock with nitric

acid. This is the nitrophosphate route leading to NPK fertilizers; as in the

mixed-acid route, potassium and other salts are added during the process.

-Nitrophosphate fertilizers are also produced by the mixed-acid process,

through digestion of the phosphate rock by a mixture of nitric and

phosphoric acids.

Environmental issues associated with phosphate fertilizer

plants include the following:

1· Air emissions

2· Wastewater

3· Hazardous materials

4· Wastes

5· Noise

1· Air emissions

A) Sulphuric Acid Production: The major polluting parameters are sulphur dioxide,

sulphur trioxide and acid mist. Emissions occur during sulphur burning, in converters and

absorption.

B) Process Emissions (Phosphoric Acid Production): (a)The wet process, where phosphate

rocks are digested with an acid (e.g. sulfuric, nitric or hydrochloric acid). (b) The thermal

process, where elemental phosphorous is produced from phosphate rock, coke, and silica

in an electrical resistance furnace and is then oxidized and hydrated to form the acid.

The main emissions are gaseous fluorides and dust. Gaseous fluorides such as silicon

tetra-fluoride (SiF4) and hydrogen fluoride (HF) can be major emissions from wet process

acid production.

The reactor in which phosphate rock is reacted with sulfuric acid is the main source of

emissions.

C) Process Emissions (Superphosphate Phosphate Fertilizer Production):

Sources of emissions at a single superphosphate (SSP) plant include rock unloading and

feeding, mixing operations (in the reactor), storage (in the curing building), and fertilizer

handling operations. The major polluting parameters are total suspended particulates,

fluorides, sulphuric acid mist, dust fall and inhaled dust.

Emissions of fluorine compounds and dust particles occur during the production of

granulated triple superphosphate (TSP). Silicon tetrafluoride (SiF4) and hydrogen

fluoride (HF) are released by the acidulation reaction and they evolve from the reactors,

granulator, and dryer.

Generally; Dust emissions may be generated during unloading, handling, grinding, and

curing of phosphate rock, in addition to granulation and crushing of superphosphates.

D) Process Emissions (Compound Fertilizer Production NPK): Air emissions from NPK

include ammonia emissions, nitrogen oxides (NOX), mainly NO and NO2, nitric acid,

fluorides, aerosol emissions, including ammonium nitrate (NH4NO3), ammonium

fluoride (NH4F), and ammonium chloride (NH4Cl).

2· Wastewater Effluent

A) Effluents (Phosphoric Acid Production): It may contain a considerable amount of

impurities, such as phosphorus and fluorine compounds, cadmium and other heavy

metals, and radionuclides.

B) Effluents - Superphosphate Fertilizer Production: Contaminants may include

filterable solids, total phosphorus, ammonia, fluorides, heavy metals (e.g. Cd, Hg, Pb),

and chemical oxygen demand (COD).

C) Effluents - Compound Fertilizer Production: Effluent from NPK facilities employing

the nitrophosphate route may contain ammonia, nitrate, fluoride and phosphate.

Ammonia is found in the effluents of the condensates of the ammonium nitrate

evaporation or the neutralization of the nitro phosphoric acid solution.

D) Process Wastewater Treatment: It includes filtration for separation of filterable

solids; flow and load equalization; sedimentation for suspended solids reduction using

clarifiers; phosphate removal using physical-chemical treatment methods; ammonia

and nitrogen removal, dewatering and disposal of residuals in designated waste

landfills.

E) Other Wastewater Streams & Water Consumption

Another contaminated stream may result from condensers, heat exchangers and gas

scrubbers. It was found that the main sources of pollution are attributed to the washing

water of the scrubbing towers.

Through evaporation and recycling, contaminant concentrations in water can reach

several grams per liter of phosphates and fluoride. Additional elemental contaminants

in pond water which originate in phosphate rock are arsenic, cadmium, uranium,

vanadium, and radium.

3· Hazardous Materials

Phosphate fertilizer manufacturing plants use, store, and distribute significant amounts of

hazardous materials (e.g. acids and ammonia).

4· Solid wastes

Phosphogypsum is the most significant by-product in wet phosphoric acid production.

Phosphogypsum contains a wide range of impurities (residual acidity, fluorine

compounds, trace elements such as mercury, lead and radioactive components). The

vanadium content of the V2O2 catalysts can be reclaimed for further use.

5· Noise

Noise is generated from large rotating machines, including compressors and turbines,

pumps, electric motors, air coolers, rotating drums, spherodizers, conveyors belts, cranes,

fired heaters, and from emergency depressurization

Service Units and Related Pollution Sources

A) Boilers: Boilers are used to produce steam for: Heat supply to the processes,

reaction (steam reforming) and CO shift converter (in ammonia production and

other processes utilizing steam). Electric power generation.

B) Water Treatment Units: Water Softening for medium hardness water, Water

softening for very high bicarbonate hardness, Water Demineralization

C) Cooling Towers: Cooling towers provide the means for recycling water and thus

minimizing its consumption.

D) Compressors: Several types of compressors are needed in the fertilizers plants,

including the ammonia, steam, gas and air compressors.

E) Laboratories: Research laboratory, Quality control laboratory, Environmental

laboratory

Service Units and Related Pollution Sources

F) Workshops and Garage

G) Storage Facilities: Acids such as sulphuric or nitric or phosphoric acids are stored in

large capacities tanks

H) Wastewater Treatment Plants

The effluent streams can be characterized as either a phosphoric acid effluent or an

ammonia effluent. The phosphoric acid effluent is high in fluoride concentration, low in

pH, high in phosphate and in suspended solids. The two-stage fluoride removal process

of lime precipitation followed by alum-polyelectrolytes flocculation and sedimentation

was found to be workable.

The other effluent type is characteristic of ammonia production and ammonia

containing products. These effluents require a pH adjustment and settling.

Example of Chemical Fertilizer Industry

1. Mangalore Chemicals & Fertilizers Limited, with a turnover Rs. 2,523.83

crores (2010–11), is the only manufacturer of chemical fertilizers in the state

of Karnataka, India.

The company deals with fertilizers like Diammonium phosphate.

The company has capacity to manufacture 3,79,500MT of Urea, 2,55,500MT of

Phosphatic fertilizers.

The Phosphatic plant was designed and engineered by Toyo Engineering

Corporation, Japan.

As an ISO 14001 certified Company, the company installed waste water

recovery facility to treat, recycle and reuse the entire quantity of sewage and

process effluents, thereby achieving zero liquid effluent discharge

Zero Discharge Technologies

These ZLD Systems can recycle more than 90 % of waste water.

Zero Discharge Technologies:

- Reverse Osmosis - Reverse osmosis & microfiltration treatment – Nanofiltration -

Ion Exchange Treatment - ZLD Water Softener

ZLD Application Areas:

Metals & Mining- Power Generation- Alumina Industry- Fertilizer production-

Textile Production- Food & Beverage factory- Dairy production- Waste

management- Oil & Gas- Environment- Hydrocarbon Processing- Pulp and Paper-

Chemical Processing- Pharmaceutical

Assignment Search for a published manuscript with a topic of Zero Liquid Discharge systems. Every student will discuss the paper within 5 min, as follows: Introduction (1 min) Materials and methods (1 min) Important results (1 min) Advantages (1 min) Disadvantages (1 min) Then, Q&A with other students for 5 min