DESIGN CRITERIA OF BIOFILTER SYSTEM AS TREATMENT FOR DOMESTIC

WASTEWATER

AFIQ AIMAN BIN MOHAMAD RAZAK

A reported submitted in partial fulfillment of the requirements for the award of the

degree of Bachelor of Civil Engiheering

Faculty of Civil Engineering & Earth Resources

Universiti Malaysia Pahang

DECEMBER 2010

ABSTRACT

Nowadays, the effluent from domestic wastewater is highly untreated. So

when the effluents flow to the river it will cause water pollution and will affect water

quality of the river. If the water polluted, the aquatic life and environment surrounding

will be in deep trouble. A device known as biofilter can help this problem solve. To

make this biofilter effective, it will depend on the design. The optimum design criteria

will make this biofilter become more effective although in the market nowadays have

many biofilter but the available biofilter now is doesn't have proper design criteria.

This study aims to determine the design criteria of biofilter as treatment for domestic

wastewater and to evaluate the effectiveness of biofilter as treatment for domestic

wastewater. This study involves two main methods which are field measurement and

laboratory experiments. Field measurement includes test for Dissolved Oxygen (DO),

Total Dissolved Solid (TDS), pH, temperature, salinity, turbidity and electric

conductivity while laboratory experiments involve test for Biochemical Oxygen

Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS),

Ammonia Nitrogen (AN), Total Coliform, E-Coli and Oil and Grease. All the results

were compare with Standard A and Standard B, Environment Quality Act, 1974 and

analyzed in terms of percentages of removal. The study indicates that the design

criteria adopted not shows an excellent performance where most of the water quality

parameters not complying Standard A and Standard B, Environment Quality Act,

1974, however it do shows improvement in terms of percentage of removal for

parameters turbidity, total suspended solid and ammonia nitrogen The percentage

removal of turbidity as high as 98.99%, while TSS and AN range from 31.25% to

58.55%.

V

vi

ABSTRAK

Dewasa ini, efluen dari air sisa domestik sangat tercemar. Apabila efluen sisa

domestik dilepaskan dan mengalir ke sungai, Ia akan menyebabkan pencemaran air

dan akan menjejaskan kualiti air sungai. Jika pencemaran air berlaku, ia akan

mengancam hidupan akuatik dan persekitaran sekililing juga akan mengalami masalah

yang besar. Justeru itu, satu alat yang dikenali sebagai 'Biofilter' boleh menyelesaikan

masalah mi dan ia bergantung pada reka bentuk 'Biofilter'. Reka bentuk 'Biofilter'

yang optimum akan mernbuatkan ia menjadi lebih efektif walaupun pada hari mi

terdapat banyak 'Biofilter' dijual dipasaran tetapi 'Biofilter' yang sedia ada di pasaran

tiada reka bentuk yang tetap. Oleh itu, tujuan kajian mi dijalankan ialah untuk

menentukan satu reka bentuk 'Biofilter'sebagai alat utuk merawat air sisa domestik

dan untuk menilai keberkesanan 'Biofilter' sebagai alat untuk merawat air sisa

domestik. Terdapat dua kaedah yang dilakukan di dalam kajian mi iaitu ujian di tapak

dan ujian di malcmal. Ujian di tapak meliputi penganalisaan Oksigen Terlarut (DO),

Bahan Pepejal (TDS), pH, suhu, kekeruhan, kemasinan dan konduktiviti elektrik

manakala ujikaji di makmal ialah Permintaan Oksigen Biokimia (BOD), Permintaan

Oksigen Kimia (COD), Pepejal Terampai (TSS), Ammonia Nitrogen (AN), Total

Koliform, E-Coli dan Minyak dan lemak. Selepas ditapis oleh 'Biofilter' dan ujikaji

makmal, hasilnya akan dibandingkan dengan Standard A dan Standard B, Akta Kualiti

Persekitaran, 1974. Peratus penyingkiran kekeruhan ialah setinggi 98.99% manakala

pepejal terampai dan ammonia nitrogen ialah dan 31.25% sehingga 58.5%.

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLES OF CONTENT vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS AND ABBREVIATIONS xiv

LIST OF APPENDICES xvi

1 INTRODUCTION

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objectives Of The Study 3

1.4 Scope Of Study 4

1.5 Location Of Study 5

1.6 Significant Of Study 6

VII

VIII

2 LITERATURE REVIEW

2.1 Introduction 7

2.2 Water Pollution 8

2.3 Domestic Wastewater 9

2.4 Wastewater Characteristic 11

2.5 Wastewater Treatment Device 12

2.6 Biofiltration 13

2.7 Timeline Of Biofilter 14

2.8 Biofilter Design 15

2.9 Past Research Of Biofilter 19

2.10 Factor Effecting Biofilter Performance 20

2.10.1 Packing Media 20

2.10.2 Moisture Content 20

2.10.3 Temperature 21

2.10.4 Oxygen Content 22

2.10.5 pH 23

2.10.6 Nutrients 23

2.10.7 Pressure Drop 24

2.10.8 Medium Depth 25

2.10.9 Waste Gas Pre-Treatment 26

2.10.10 Maitenance 26

2.11 Biofilter Market 27

2.11.1 Bioclear 400 S (Biosand) 27

2.11.2 Bioclear 400 SC (Biosand &Biocarbon) 28

2.11.3 Bioclear 400 SCO 29

2.11.4 Ecoflo®Biofilter 30

ix

3 METHODOLOGY

3.1 Introduction 32

3.2 Flow Chart 33

3.3 Experimental Setup 34

3.4 Design Detail Of Biofilter System 35

3.5 Filtering Material 38

3.5.1 Sponge 39

3.5.2 Empty Fruit Bunch (EFB) 40

3.5.3 Mudball 41

3.5.4 Sand And Coarse Gravel 42

3.5.5 Activated Carbon 42

3.5.6 Charcoal 44

3.6 Water Quality Parameters 45

3.6.1 Biochemical Oxygen Demand (BOD) 45

3.6.2 Chemical Oxygen Demand (COD) 45

3.6.3 Temperature 47

3.6.4 pH 47

3.6.5 Dissolved Oxygen (DO) 48

3.6.6 Electric Conductivity 49

3.6.7 Turbidity 50

3.6.8 Salinity 51

3.6.9 Total Suspended Solid (TSS) 51

3.6.10 Total Dissolved Solid (TDS) 52

3.6.11 Ammonia Nitrogen (AN) 53

3.6.12 Oil And Grease 53

3.6.13 Totak Coliform And E-Coli 54

3.7 Water Quality Sampling 54

X

4 RESULT AND ANALYSIS

4.1 Introduction 55

4.2 Analysis Of Results 56

4.2.1 pH 56

4.2.2 Dissolved Oxygen (DO) 57

4.2.3 Temperature 58

4.2.4 Electric Conductivity 60

4.2.5 Salinity 62

4.2.6 Total Dissolved Solid (TDS) 63

4.2.7 Turbidity 65

4.2.8 Biochemical Oxygen Demand (BOD) 67

4.2.9 Chemical Oxygen Demand (COD) 69

4.2.10 Ammonia Nitrogen (AN) 70

4.2.11 Total Suspended Solid (TSS) 72

4.2.12 Oil And Grease 75

S CONCLUSION AND RECOMMENDATIONS

5.1 Introduction 77

5.2 Conclusion 78

5.3 Recommendation 79

REFERENCES 81

APPENDICES 89

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Performance of parameters 31

3.1 Mechanism and function of filtering material 38

4.1 Result of pH 56

4.2 Result of Dissolve Oxygen (DO) 57

4.3 Result of temperature (°C) 59

4.4 Result of electric conductivity (ms/cm) 61

4.5 Result of salinity (mgfL) 62

4.6 Result of TDS (mgfL) 64

4.7 Result of turbidity (NTU) 65

4.8 Result of BOD (mg/L) 68

4.9 Result of COD (mg/L) 69

4.10 Result of AN (mg/L) 71

4.11 Result of SS (mg/L) 73

4.12 Result of Oil and Grease (mg/L) 75

XI

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Location of study area 5

1.2 Wastewater's discharge point at KK3 6

2.1 Typical composition of untreated domestic 11

wastewater

2.2 Percentage of BOD removal 19

2.3 Percentage of COD removal 19

2.4 Treatment of Iron, Parasites, Colour, Cysts, 28

Manganese, Arsenic, Lead and Mercury & Turbidity

2.5 Treatment of Dissolved Organic Carbon, Tannins, 29

Pesticides, Iron Bacteria, and Colour & Odours

2.6 Treatment of taste and odour problems and highly 30

contaminated water sources and used in conjunction

with BioSand and BioCarbon.

3.1 Flow chart of methodology 33

3.2 Experimental Site 35

3.3 Schematic diagram 37

3.4 Sponge 39

3.5 Empty Fruit Bunch (EFB) 40

3.6 Mudball 41

3.7 Filtering material in second layer 42

3.8 Activated carbon 43

3.9 Charcoal 44

3.10 Equipmennt for COD test 47

XII

3.11 pH meter 48

3.12 Dissolve oxygen meter 49

3.13 Turbidity checker 51

4.1 pH value 56

4.2 Dissolve Oxygen Value 58

4.3 Temperature value 59

4.4 Electric conductivity value 61

4.5 Salinity value 63

4.6 Total dissolved solid value 64

4.7 Turbidity value 66

4.8 Percentage removal of turbidity 66

4.9 BOD value 68

4.10 COD value 69

4.11 AN value 71

4.12 Percentage removal of AN 72

4.13 Total suspended solid value 74

4.14 Percentage removal of SS 74

4.15 Oil and grease value 75

XIII

LIST OF SYMBOLS AND ABBREVIATIONS

AN - Ammonia Nitrogen

BOD - Biochemical Oxygen Demand

CM - Centimetre

COD - Chemical Oxygen Demand

DO - Dissolved Oxygen

EFB - Empty Fruit Bunch

EM - Effective Microorganism

FKASA - Fakulti Kejuruteraan Awam dan Alam Sekitar

KK3 - Kolej Kediaman 3

M - Metre

Mcm - Million cubic meter

Mc rn/year - Million cubic meter per year

Cm/day - Centimetre per day

NRE - Natural Resources and Environment

NTU - Nephelometric Turbidity Units

P - Dilution Factor

pH - Hydrogen-ion Concentration

PPT - Parts per Thousand

TDS - Total Dissolved Solid

TSS - Total Suspended Solid

TOD - Total Oxygen Demand

UMP - Universiti Malaysia Pahang

VOC - Volatile Organic Compound

WQI - Water Quality Index

Ag2SO4 - Argentums sulphate

°C - Degree of Celsius

xiv

xv

Ca - Calcium

I{2SO4 - Sulphuric acid

HgSO4 - Mercuric sulphate

K - Potassium

K Cr 0 - Potassium dichromate 2 2 7

gall&/day - Gallon per feet square per day

Mg - Magnesium

Mg/L - Miligram per liter

Ms/cm - MiliSiemen per centimetre

Na - Sodium

NaCl - Sodium Chloride

- Volume of sample

- V Volume of dilution water dw

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Third Schedule, Environmental Quality Act 88

B Results of laboratory and in-situ test 89

C Results percentage of removal 90

D Site of study 91

E Biofilter 92

xvi

CHAPTER 1

INTRODUCTION

1.1 General

Water is an important element for all human beings in the world. Our body

consists mostly of the water. We need water for drinking, cooking, washing,

agriculture and to run our industries. We usually take it for granted because of its

availability; but when in scarcity it becomes our most precious resource (Che-Ani et

al., 2009).

Water pollution is a major problem in the global context. It has been suggested

that it is the leading worldwide cause of deaths and diseases and that it accounts for

the deaths of more than 14,000 people daily (West, 2006). Water pollution may be

analyzed through several broad categories of methods: physical, chemical and

biological. Most involve collection of samples, followed by specialized analytical

tests. Some methods may be conducted in situ, without sampling, such as temperature.

Government agencies and research organizations have published standardized,

validated analytical test methods to facilitate the comparability of results from

disparate testing events (Clescerl et al., 2007).

2

Wastewater is any water that has been adversely affected in quality by

anthropogenic influence. It comprises liquid waste discharged by domestic residences,

commercial properties, industry, and/or agriculture and can encompass a wide range

of potential contaminants and concentrations. In the most common usage, it refers to

the municipal wastewater that contains a broad spectrum of contaminants resulting

from the mixing of wastewaters from different sources.

A biological filter technology is used to control water pollution by applying

the use of microorganisms as agents to treat contaminated water. This method

introduced by Shimanto Gawa has been successfully applied in Japan. The biofilter

reliance on microorganisms requires an appreciation of ecological concepts which

must be considered in biofilter design (Nur, 2007).

1.2 Problem Statement

Nowadays, the effluent from domestic wastewater is highly untreated. So

when the effluents flow to the river it will cause water pollution and will affect water

quality of the river. If the water polluted, the aquatic life and environment surrounding

will be in deep trouble. A device known as biofilter can help this problem solve. To

make this biofilter effective, it will depend on the design. The optimum design criteria

will make this biofilter become more effective although in the market nowadays have

many biofilter but the available biofilter now is doesn't have proper design criteria.

Sewage water pollution is a type of water pollution and one of the major

problems in cities. The sewage water is drained off into rivers without treatment. The

careless disposal of sewage water leads to a chain of problems, such as spreading of

3

diseases, eutrophication, increase in Biological Oxygen Demand (BOD) and many

more. The waste water that flows after being used for domestic, industrial and other

purposes is termed as sewage water. In ideal situations, the sewage water is

channelled or piped out of cities for treatment. Bulk of the sewage contains water as

the main component, while other constituents include organic wastes and chemicals.

After the biological treatment, the partially pure effluent is treated with

chemical disinfectants. The water treated in the treatment plants can be . used in golf

courses for watering the lawns and in agriculture for irrigation. Some sewage

treatment plants are very efficient and produce clear and clean water at the end of the

process. Sewage water treatment is a must, when environmental issues are an

increasing concern. An effort needs to be taken to purify the effluents. It will not only

benefit human beings but also the varied flora and fauna on our planet. Let's pledge to

keep our environment beautiful and free from any kind of pollution (Shashank, 2009).

1.3 Study Objectives

The objectives of this study are:

I. To determine the design criteria of biofilter criteria as treatment for domestic

wastewater.

II. To evaluate the effectiveness of biofiter as treatment for domestic wastewater.

4

1.4 Scope of Studies

I. Proposed new modification system design and new of biological filter medium

for waste water treatment.

II. Setup the model of this system at drainage near with KK3 hostel and conduct

water quality testing at Environmental Laboratory, Fakulti Kejuruteraan

Awam dan Alam Sekitar (FKASA), Universiti Malaysia Pahang (UMP).

III. Collection of waste water samples effluent from drainage system located near

student residential area (KK3), UMP.

IV. Laboratory water quality testing for water quality parameters which are BOD,

COD, Oil and Grease, Ammonia Nitrogen, TSS, E-Coli, Total Coliform and

compare with standard A and standard B of Environmental Quality Act (1974).

V. In-situ water quality testing for parameters which are DO, pH, electric

conductivity, salinity, turbidity, TDS, temperature and compare with standard

A and standard B of Environmental Quality Act (1974).

5

1.5 Location of study

The biofilter is located at the point sources of wastewater treatment. Figure 1.1

shows the location of biofilter at Universiti Malaysia Pahang (UMP), while Figure 1.2

shows the waste water's discharge point at KK3.

Figure 1.1: Location of study area

I " I . -.

II )\ ( 11

I -

ILaboratory Biofilter

'-A I ••- --- •1 - ' -1

Faculty.k

-. - .-.- . - - - - ....L - ...-L - •- - . -...."

4 .t c:-' ' KK3

0-' ,'-J!

Main Enterance

:

,, 7 (( I

LiLT4/)01 V

Til. IF

\: ) .- ,j:-ea

'if --

Figure 1.2: Waste water's discharge point at KK3.

1.6 Significance of Study

Biofiltration is a pollution control technique using living material to capture

and biologically degrade process pollutants. Common uses include processing waste

water, capturing harmful chemicals or silt from surface runoff, and microbiotic

oxidation of contaminants in air. The use of indigenous microorganism enables this

system to operate this minimal maintenance due to its biological regeneration, thus

this system serve as sustainable, effective and economic filtration method in various

waters and discharges for the improvement of water quality. The biofilter can be very

useful in various waste water due to the efficiency for biological purification, good

integration in environment and low sludge production.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Water pollution in Malaysia is an environmental problem that facing serious

problem from a day to another day and until now there is no effective ways to reduce

the water pollution level. Pollution occurs when there are impurities in the water such

as sediment (suspended solid), nitrate, heavy metal and others. The presence of

impurities can affect all living things that rely on river water resources.

Wastewater quality can be defined by physical, chemical, and biological

characteristics. Physical parameters include color, odour, temperature, solids

(residues), turbidity, oil, and grease. Solids can be further classified into suspended

and dissolved solids (size and settle ability) as well as organic (volatile) and inorganic

(fixed) fractions. Chemical parameters associated with the organic content of

wastewater include the biochemical oxygen demand (BOD), chemical oxygen demand

(COD), total organic carbon (TOC), and total oxygen demand (TOD). BOD is a

measure of the organics present in the water, determined by measuring the oxygen

necessary to biostabilize the organics (the oxygen equivalent of the biodegradable

8

organics present). Inorganic chemical parameters include salinity, hardness, pH,

acidity, alkalinity, iron, manganese, chlorides, sulfates, sulfides, heavy metals

(mercury, lead, chromium, copper, and zinc), nitrogen (organic, ammonia, nitrite, and

nitrate), and phosphorus. Bacteriological parameters include coliforms, fecal

coliforms, specific pathogens, and viruses.

A biological filter technology is used to control water pollution by applying

the use of microorganisms as agents to treat contaminated water. This method

introduced by Shimanto Gawa has been successfully applied in Japan. The biofilter

reliance on microorganisms requires an appreciation of ecological concepts which

must be considered in biofilter design (Nur Eezani, 2007).

2.2 Water Pollution

There are strategies to propel country's growth trends towards sustainable

development which embodies the three pillars which are economic development,

social development and environment protection. Realizing the importance to facilitate

a coordinated and comprehensive approach in managing natural resources and

environment, the Ministry of Natural Resources and Environment (NRE) was formed

in 2004. With regards to the water pollution, generally in Malaysia it is caused by

point and non-point sources. Point sources comprise sewage treatment plants,

manufacturing and agro-based industries as well as animal farms. Non-point sources

are made up of diffused sources such as agricultural activities and surface runoffs

(National Policy on the Environment, 2002).

According to the study commissioned by ASEAN Secretariat and AusAID

presented in the Report on State of Water Resources Management in ASEAN 2005,

the total available internal water resources for Malaysia are 630,000 mcmlyear. It is

estimated for the year 2025, the total demand for sector such as industry, agriculture,

irrigation and domestic is 14,504 mcm compared to 1,622 mcm for the current

demand.

Rapid development has created gaps in the prevention of pollution and the

highly dense population in urban centres has converted rivers into open sewers. Cities

are well known for being polluters of aquatic environment with sewage and municipal

wastewater, industrial effluent and polluted urban runoff. Similarly, the farming

communities pollute the aquatic environment with irrigation returns that contain

fertilisers and pesticides, and animal wastes. River water quality is also degraded by

sediments from land clearance and solid wastes. Water pollution disrupts water supply

services, affects human health and destroys aquatic lives and habitat. The 'Love Our

Rivers' campaign was launched in 1993 with the aim of improving awareness among

the general public including school children, and the relevant authorities on the need

to preserve rivers. The campaign is a joint effort by government agencies, NGOs,

private sector and general public. It is carried out through river adoption and river

watch programmes, river expeditions, educational talks, river beautification, seminars

and the promotion of water conservation through the mass media (Raja Zaharaton,

2004).

2.3 Domestic Wastewater

As the country grows so does the problem of providing sufficient clean water

to the population and until about five decades ago, Malaysia's waste disposal system

was no different from what is still found in many developing countries. Malaysia's 27

million people generate about six million tons of sewage every year, most of which is

treated and released into the rivers. Proper treatment of sewerage is paramount as

about 98% of Malaysia's fresh water supply comes from surface water. Raw surface

10

water becomes contaminated as a result of excessive and indiscriminate discharge of

wastewater directly from households or factories to drains and into rivers with

minimal or no treatment. This impairment of water quality greatly reduces the

usability of the water for ordinary purposes or in a worst case scenario creates a

hazard to public health through poisoning or the spread of diseases. To combat this,

around 8,000 public sewage treatment plants, 500 network pumping stations, 17,000

kilometres of underground sewerage pipes and half a million household septic tanks

connected to the sewers. In response to the increasing demand for a better and

effective sanitation services, private companies were encouraged by the government

to build wastewater management systems (APEC, 2009).

Municipal wastewater is comprised of domestic (or sanitary) wastewater,

industrial wastewater, infiltration and inflow into sewer lines, and storm water runoff.

Domestic wastewater refers to wastewater discharged from residences and from

commercial and institutional facilities (Metcalf and Eddy, Inc. 1991). Domestic water

usage, and the resultant wastewater, is affected by climate, community size, density of

development, community affluence, dependability and quality of water supply, water

conservation requirements or practices, and the extent of metered services. Metcalf

and Eddy, Inc. (1991) provide details on the influence of these factors. Additional

factors influencing water use include the degree of industrialization, cost of water, and

supply pressure (Qasim, 1985). One result of the combined influence of these factors

is water use fluctuations. About 60 to 85% of water usage becomes wastewater, with

the lower percentages applicable to the semiarid region of the south western United

States (Metcalf and Eddy, Inc. 1991).

11

2.4 Wastewater Characteristic

Municipal wastewater is mainly comprised of water (99.9%) together with

relatively small concentrations of suspended and dissolved organic and inorganic

solids. Among the organic substances present in sewage are carbohydrates, lignin,

fats, soaps, synthetic detergents, proteins and their decomposition products, as well as

various natural and synthetic organic chemicals from the process industries. Figure 2.1

shows the typical concentration range of various constituents in untreated domestic

wastewater. Depending on the concentrations, wastewater is classified as strong,

medium or weak (Clescerl et al., 2007)

- -. - - Concentration

* - Contaminants

- Unit -

Low strength

Medium strength

High . sirength.

Solids, total (TS) mg/I 390 720 1230 Dissolved. total )TDS) mg/I 270 500 860

Fixed Org/I 160 300 520 volatile mg/I 110 200 340

Suspended solids, total (TSS) mg/I 120 210 400 Fixed mg/L 25 50 85 Volotilrx org/I 95 160 315

Settleable solids n,I/I 5 10 20 Biochemical oxygen demand, 5-d, 20cC (800,, 20CC) rag/I 110 190 350 Total organic cm-ban (OC) nrg/L 80 140 260 Chemical oxygen demand (COD) mg/I 250 430 800 Nitrogen (total as N) mg/I 20 40 70

Organic mg/I 8 15 25 Free ammonio mg/I 12 25 45 Nitrites mg/I 0 0 0 Nitrates mg/I 0 0 0

Phosphorus (total as P) mg/I 4 7 12 Organic mg/I 1 2 4 Inorgank ru/I 3 5 10

Chloridest mg/I. 30 50 90 Srtlfate1 mg/I 20 30 50 Oil and grease mg/I 50 90 100 Volatile Organic compounds (VOCs) mg/I <100 100-400 >400 Total colilorm No./100 aL 101O° 107_1010 Feral coliForm No./100 aL 103-10' 10-10 iO'-lO° C.ypfosporidun, oocysls No./100 ml 10-1-100 1 O-10 10-1-102 Gk.rdio lamb/i. cysts Ncr/lOU mL 10-110 10-1-102 10-"10

d Low strength is based on on approximate wastewater IlOwrotC of 750 l/copito-d (200 gol/copirwd). Medium strength is hosed on on approximate wastewater towramo of 460 L/rapito-d (120 gol/copito.d). High strength is based on on approximate wastewater flowrotx of 240 I/cnpilO-d (60 gol/copita.d(. 5 V0 1 005 should be increased by amount OF conStituent present in domestic water supply. Nato mg/I. = 9/m3.

Figure 2.1: Typical composition of untreated domestic wastewater

(Source:https://dspace.ist.utl.ptlbitstreanil2295/1 63262/1 /IT_Caracterizacao_qualitativ

a_aguas_residuais_2_.pdf)