CYPRUS INTERNATIONAL UNIVERSITYINDUSTRIAL WASTE WATER TREATMENT (OIL REFINERY)

ByELEGBELEYE OLADIPO AYODAMOPE (20143234)

INTRODUCTION

PROCESS UNITS FOUND IN A REFINERY

OVERVIEW OF OIL REFINERY WASTE PRODUCTION

REFINERY WATER

REFINERY WASTEWATER TREATMENT

WASTEWATER TREATMENT SCHEME

Environmental Standards for Petroleum Oil Refineries Effluent

PUBLIC HEALTH CONCERNS

Dissolved Air Flotation

Activated Sludge

Nitrification With Denitrification

CONCLUSION

An oil refinery is an industrial process plant where crude oil is processed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas.

Oil refineries are typically large, sprawling industrial complexes with extensive piping running throughout, carrying streams of fluids between large chemical processing units.

PROCESS UNITS FOUND IN A REFINERY

•De-salter unit washes out salt from the crude oil before it enters the atmospheric distillation unit.•Atmospheric distillation unit distills crude oil into fractions. •Vacuum distillation unit further distills residual bottoms after atmospheric distillation.•Naphtha hydro-treater unit uses hydrogen to desulfurize naphtha from atmospheric distillation. Naphtha is hydro-treat ed before sending to a catalytic reformer unit.•Catalytic reformer unit is used to convert the naphtha-boiling range molecules into higher octane reformate (reformer product).The reformate has higher content of aromatics and cyclic hydrocarbons). An important byproduct of a reformer is hydrogen released during the catalyst reaction. The hydrogen is used either in the hydrotreaters or the hydrocracker.•Distillate hydrotreater desulfurizes distillates (such as diesel) after atmospheric distillation.•Fluid Catalytic Cracker (FCC) unit upgrades heavier fractions into lighter, more valuable products.•Hydrocracker unit uses hydrogen to upgrade heavier fractions into lighter, more valuable products.

Overview of Oil Refinery Waste Production

The generation of waste is an inevitable consequence of the operation of refineries and depots. Waste production in refineries and terminals represents a high operating cost and as such its minimization should be a priority. Waste substances generated by oil refineries fall into two categories:

• Non-hazardous waste, e.g. scrap metal, spent catalytic cracking catalyst or “domestic” waste.

• Hazardous waste, e.g. asbestos, acid tars, sludge with a high lead content or many oil contaminated materials such as untreated waste water discharges.

Refinery Wastewater Treatment

• In a refinery wastewater treatment system, two steps of oil removal are typically required to achieve the necessary removal of free oil from the collected wastewater prior to feeding it to a biological system.

• This oil removal is achieved by using an APIseparator followed by a dissolved air flotation (DAF) or induced air flotation (IAF) unit

The wastewater from the secondary oil/water separation unit is sent to the equalization system that is used to dampen out variations in flow and concentration in the refinery wastewater.

Refinery Wastewater Treatment cont’d

• The wastewater is then routed to the aeration tank/clarifier which constitutes the biological system

The effluent from the clarifier is then sent to tertiary treatment (if necessary) prior to discharge.

S/N

Parameter

Limiting value for concentration(mg/l, except for pH)

Limiting value for quantum (kg/1000 tonne of crude processed, except for pH)

1 Ph 6.0 – 8.5 -

2 Oil and Grease 5 2

3 BOD3, 27o C 15 6

4 COD 125 50

5 SS 20 8

6 Phenol 0.35 0.14

7 Sulphide 0.5 0.2

8 CN 0.2 0.08

9 Ammonia as N 15 6

10

TKN 40 16

11

P 3 1.2

12

Cr(VI) 0.1 0.04

13

TOTAL (Cr) 2.0 0.8

14

Pb 0.1 0.04

15

Hg 0.01 0.004

16

Zn 5.0 2

17

Ni 1.0 0.4

18

Cu 1.0 0.4

19

V 0.2 0.8

20

Benzene 0.1 0.04

21

Benzo(a)Pyrene 0.2 0.8

Water and solid wastes emanating from refineries has damaging effect on public health and the environment when pollution parameters are above the set standards.

Localized waste water discharges and habitat degradation contaminate water supplies, farming lands and fisheries in poor regions of Ecuador and the Niger River Delta.

Cancer-causing chemicals such as benzene primarily affect the health of those living in close proximity to refineries.

Populations living in inner cities often suffer most from concentrated air pollution -- soot and ozone -- due to the proximity with truck and bus routes.

Dissolved Air Flotation

• The first step in a DAF system is coagulation/ flocculation. Dispersed particles (oil/solids) are stabilized by negative electric charges on their surfaces, causing them to repel each other.

• they do not settle, since this prevents these charged particles from

colliding to form larger masses, called flocs.

• Chemical coagulation and flocculation are required to assist in the removal of colloidal particles from suspension.

• These processes, usually done in sequence, are a combination of physical and chemical procedures.

Dissolved Air Flotation—a Typical DAF Unit

Activated Sludge

• An activated sludge process is the most effective of all the biological systems available

• It is used in many refineries around the world and offers a reliable method of biological treatment.

• Activated sludge is a continuous suspension of aerobic biological growths in a wastewater containing entrapped suspended colloidal, dissolved organic and inorganic materials.

The PACT® (Powdered Activated Carbon Treatment) system

Nitrification With Denitrification

The biological treatment system could include either a nitrification(by the use of nitrifying bacteria) or a combined nitrification/denitrification step in some cases when a refinery site is required to meet tight ammonia or nitrogen limits.

The level of nitrogen compounds in refinery wastewater can be controlled by avoiding discharges of spent amines and proper removal of ammonia in the sour water stripper.

Nitrification is the term used to describe the two-step biological process in which ammonia (NH4-N) is oxidized to nitrite (NO2-N) and the nitrite is oxidized to nitrate (NO3-N).

Nitrification

Nitrification With Denitrification

• In denitrification, the nitrate is reduced to nitric oxide, nitrous oxide and nitrogen gas.

Oil has many benefits and energy is necessary for all our activities. But each stage in its life cycle carries hazards for humans, wildlife and the environmental systems on which we and other species depend.

Understanding the health and environmental consequences of oil use may help decision makers assess the true costs of our dependence on this non-renewable resource hence one major reason why there is the ultimate need to treat our water and wastewater discharges emanating from all oil refineries to meet set international standards.

Reference Gary, James H., Glenn E. Handwerk, and Mark J. Kaiser. Petroleum refining: technology and economics. CRC press, 2007.

• Leffler, William L. "Petroleum refining for the nontechnical person." (1985).

• The Environment (Protection) Rule, 1986 are referred to as principal rules in all subsequent Notifications beginning with S.O. 32(E), dated 16.2.1987 published in the Gazette No. 66, dated 16.2.1987

. • EPA Notification [G.S.R 186(E), dt. 18th March, 2008]

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