Assessment of the arise situation and characteristics of sewage sludge from the wastewater treatment plants in hanoi

One member limited liability company of Hanoi Drainage undertake of solid waste gathering, management and treatment of urban sewage sludge volumes of Hanoi but just stop at the level of

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

DANG XUAN HAO

TOPIC TITTLE:

ASSESSMENT OF THE ARISE SITUATION AND CHARACTERISTICS

OF SEWAGE SLUDGE FROM

THE WASTEWATER TREATMENT PLANTS IN HANOI

BACHELOR THESIS

Study Mode : Full-time

Major : Environmental Science and Management

Faculty : International Training and Development Center

Batch : 2011-2015

Thai Nguyen, Sept 2015

ABSTRACT

Student ID DTN1153110019

Thesis Title Assessment of the arise situation and characteristics

of sewage sludge from the wastewater treatment plants in Hanoi

Supervisor (s) Prof Dr Nguyen The Dang

Abstract:

The sewage sludge is an object of most attention today The biological sewage sludge has the potential to re-use for various purposes because principal components of sewage sludge is the excess microbial of bioremediation processes with high content of organic, nitrogen and phosphorus The volume of sewage sludge of Hanoi city is increasing in both quantity and type The rivers and canals,

in addition to the role of drainage also receive a portion of municipal and industrial wastewater One member limited liability company of Hanoi Drainage undertake of solid waste gathering, management and treatment of urban sewage sludge volumes

of Hanoi but just stop at the level of sludge collected during dredging drainage ditches system, rivers and lakes Has conducted fact-finding treatment technology, sludge sources generated, sampling location at 3 treatment plants are Kim Lien, Truc Bach and North Thang Long Concurrently, find out the management of sewage sludge in the city of Hanoi to assess the situation arising sludge from wastewater treatment plants of Hanoi and assess the characteristics of sludge components from the wastewater treatment plant of Hanoi The conclusions are

sludge from sewage treatment plants have high humidity, weak alkaline pH and nutrient contents are high; content of the heavy metal in sludge from 3 water treatment plants are less than the threshold of the EEC (1986) and the threshold for hazardous waste according to QCVN 07: 2009

Key words: Waste treatment, sewage sludge, heavy metal content,

management of sewage sludge

Number of pages: 51

Date of submission: 30/09/2015

Signature of

supervisor:

ACKNOWLEDGMENT

First, I would like to express profound gratitude to Prof Dr Nguyen The

Dang, who has driven research, guidance, help me during the implementation and

completion of this thesis

I sincerely thank to dean board, teachers of Environment Faculty and International Training and Development Center of Thainguyen University of Agriculture and Forestry has been communicated, to equip for me many knowledge and valuable experience as well as create the most favorable environment to learning during four school years

I would also like to thank to the staff and workers of three water treatment plants Kim Lien, Truc Bach and North Thang Long of Hanoi has help and provide for me important documents and create favorable conditions for the me in the process of gathering documents and fieldwork

Finally, I would like to express deep gratitude to my family and friends, having always encourage and help me about materially and mentally during the study to I can finish this thesis

Due to time and capacity is limited so my thesis is inevitable shortcomings I would like to receive the instructions, comments of teachers and friends to my

thesis is more complete

Student

Dang Xuan Hao

TABLE OF CONTENTS

LIST OF TABLES 1

LIST OF FIGURES 2

TABLE OF ABBREVIATIONS 3

PART I INTRODUCTION 4

PART II REVIEW OF LITERATURE 6

1.1.The general issues of sewage sludge 6

1.1.1 Concept and classification of waste sludge 6

1.1.2 Origin, nature and characteristics of sludge 9

1.1.3 Regulations and standards on sludge 13

1.1.4 The impact of the sludge on the environment and human health 18

1.2 The sludge treatment method 21

1.2.1 Handling by incineration 21

1.2.2 Handling by landfilling method 21

1.2.3 Handling by composting biological method 22

1.2.4 Handling by recycling method 23

1.3 Management situation of urban sludge in the world and in vietnam 23

1.3.1 Sludge management in the world 23

1.3.2 Sludge management in Vietnam 25

1.4 An overview of the wastewater treatment technology and generated sludge at three treatment plants 26

1.4.1 Waste water input 26

1.4.2 Waste water treatment technology general at three wastewater treatment

stations: 30

1.4.3 Residue sludge product (sewage sludge) 34

PART III OBJECT, CONTENT AND METHODS 35

2.1 Research subjects 35

2.2 Research Content 36

2.2.1 The status of municipal sludge generated from the water treatment plant 36

2.2.2 Characteristics of sludge from the wastewater treatment plant 36

2.3 Research Methods 36

2.3.1 Collection method, synthetic material 36

2.3.2 Survey method, fieldwork 36

2.3.3 Analytical method 37

2.3.4 Methods of data processing 39

PART IV RESULTS AND DISCUSSION 40

3.1 The status of urban sludge generated from the water treatment plant 40

3.2 Physical and chemical characterization of sludge from wastewater treatment plant 41

PART V CONCLUSIONS AND RECOMMENDATIONS 48

Conclusion 48

Recommendation 48

REFERENCES 50

LIST OF TABLES

Table 1.1 Nutrient contents in sewage sludge 12

Table 1.2 Regulations of US - EPA for some heavy metals in the sludge according to intended use 13

Table 1.3 The content of organic compounds for sludge applied to agriculture of some countries 14

Table 1.4 Heavy metal content to apply sewage sludge in agriculture in some countries 15

Table 1.5 Limit values of some microorganisms in sludge as standard in some countries in the world 15

Table 1.6 Basis absolute content (H) and hazard threshold calculated according leaching concentration (Ctc) of the parameters in the sludge 17

Table 1.7 Method of sludge management in some countries 24

Table 2.1 The sampling locations and sample symbols 35

Table 2.2 The targets and methods of analysis 37

Table 3.1 Parameters of the wastewater treatment plants 40

Table 3.2: Physical and chemical characterization of sludge at 3 wastewater treatment plants 41

Table 3.3: Heavy metal (HM) content in the sludge of 3 plants 43

Table 3.4 Some regulations on permissible limits of heavy metal in soil 43

LIST OF FIGURES

Figure 2.1 Sampling locations 36

Figure 3.1 Some of nutritional components in sludge 41

Figure 3.2 Cu content in sewage sludge 45

Figure 3.4 Pb content in sewage sludge 46

Figure 3.5 Pb content in sewage sludge 47

Figure 3.6 Cr content in sewage sludge 47

URENCO : Hanoi Urban Environment Company

US-EPA : United States Environmental Protection Agency

PART I INTRODUCTION

Today, the economy - society of Vietnam is on track to grow strongly, accompanied the process of industrialization and modernization, urban is gradually expansion lead to pollution, especially the emergence of various types waste In particular, the sewage sludge is also an object of most attention today, become a burden for businesses, not only in Vietnam, but even in other countries with economy, science and technology developed in the world The collection, transportation, treatment, recycling and reuse of waste particularly sewage sludge from drainage systems and sanitation facilities in urban centers, is becoming a difficult problem for the managers most in countries of the world, particularly in countries with developing economies, including Vietnam

According to US-EPA, sewage sludge disposal costs accounted for 50% of operating costs of the treatment system The disposal and burial of sewage sludge has been causing serious environmental pollution Production of sewage sludge in the United Kingdom now is up to about 1.2 million tons dry solids and in the EU generally has about 6.5 million tons of dry solids are produced annually According

to recent studies, the biological sewage sludge has the potential to re-use for various purposes because principal components of sewage sludge is the excess microbial of bioremediation processes with high content of organic, nitrogen and phosphorus

In Vietnam, solve the environmental pollution due solid waste, hazardous waste, especially sewage sludge is a major challenge to society, with the relevant authorities and the State Also sludge of canals, drains, sewage sludge generated from factories, industrial zones, industrial facilities, etc contains many pollutants and is discharged into the environment

Currently, each day the river, lake drainage system of Hanoi should receive about

1 million m3 of waste water from industrial and handicraft villages, industrial parks, hospitals, and virtually untreated thoroughly Report of the Limited Company Drainage Hanoi, the amount of urban sewage sludge collected around cities were 167,200 tonnes, including 2,140 tonnes arising from the sewage treatment plant in 2012

Precisely because the above reasons, the realization of the thesis: " Assessment

of the arise situation and characteristics of sewage sludge from the wastewater treatment plants in Hanoi" is necessary and meaningful practices to find effective solutions of domestic waste sludge treatment

PART II LITERATURE REVIEW

1.1.The general issues of sewage sludge

1.1.1 Concept and classification of waste sludge

 Concept:

The sludge is mixture with water and solid components, uniformity in the entire volume, particle size is usually smaller than 2 mm and water content (moisture) is greater than 70% Sewage sludge is the components removed from the wastewater treatment plant, consists of waste, sand, foam, solids and biosolids, the components are recovered from the manholes of the sewer system, waste by dredging canals, ditches, ponds urban Six types of sewage sludge often arises in the wastewater treatment process are sewage sludge in the the drainage system of urban domestic waste, sewage sludge from the drainage system of industrial waste, sewage sludge from the activities of dredging canals periodically, sewage sludge from septic tanks (mud tunnels), sewage sludge from the station/water treatment plants and sewage sludge from the construction work

US-EPA (Environmental Protection Agency of USA) defines sludge as the final product is generated from the wastewater treatment process of civil and industrial waste water, from sewage treatment plants in the mixed semi-solid form This term is also sometimes used as an umbrella term for separate solids suspended

in water, mixed material often contain significant amounts of water between the gaps of the solid particles The wastewater treatment process leading to the separation of contaminants and convert them into smaller phase volume (mud) Thus, after processing and sewage treatment, clean water can be reused, sludge will

be disposed of The disposal of sewage sludge and remove sludge is difficult because large amount, different components, high humidity and mud are difficult to filter Sludge treatment costs accounting for approximately 25-50% of the total cost

of waste management

The term "sludge" is already defined in the legal documents in Vietnam under the National Technical Standards on hazardous threshold for sludge from the water treatment (QCVN 50:2013/BTNMT)

Sludge from waste water drainage systems in urban centers are liquid residues, special or paste form is generated by the move and transform of wastewater in sewers, is a mixture of organic and inorganic matter include all types of mud collected from urban drainage pipe, was seen as a byproduct of the process should

be handled Sludge consists mainly of water, minerals and organic matter

Sludge can contain volatile substances, pathogenic microorganisms, bacteria, heavy metals, inorganic ions with toxic chemicals from industrial waste, household chemicals and pesticides The amount of sludge increases with the level of population growth and production growth Quantity of sludge often very large and polluting the environment if not handled well (Lawrence et al., 2010)

 Classification:

Sludge is classified based on the origins and components of them

- Classification by origin, including

+ Sludge from the domestic wastewater treatment station, treatment plant; + Sludge from the industrial wastewater treatment station, treatment plant;

+ Sludge from water drainage systems: mud drains, canals, rivers and lakes dredging sludge;

+ Sludge from manholes, septic tanks;

+ Sludge from the construction site

- Classification by components: Component of sludge depends on the nature

of initial water pollution and cleaning methods: physical, physical chemistry, biology handling Specific:

+ Hydrophilic organic sludge: It is the most common kind, the difficulty of drying the sludge is due to the presence of the majority of hydrophilic colloids In this kind, all sludge biological treatment of waste water, volatile matter content which can reach 90% of the entire dry matter (wastewater from the food industry, organic chemistry)

+ Hydrophilic inorganic sludge: The sludge contains hydroxide metal formed

by chemical methods of precipitating metal ions in water treatment (Al, Fe, Zn, Cr)

or by the use of inorganic flocculation (iron salts, aluminum salts)

+ Sludge containing oil: In the sludge with a small amount of oil or mineral grease (or animal) These substances in the form of emulsions or absorb mud hydrophobic elements Part of biological sludge can also be present in case the final treatment with activated sludge, such as wastewater of refineries)

+ Hydrophobic inorganic sludge: the sludge is characterized by a more excels proportion than other substances, special substances have small levels of water retention (sand, silt, ash, salt has crystallized)

+ Hydrophilic - hydrophobic inorganic sludge: The sludge primarily consists

of hydrophobic substances containing hydrophilic substances sufficient to cause adverse effects to the drying sludge The hydrophilic substances are usually metal hydroxide (aggregates)

+ Sludge have fiber: This type is often very easy to dry unless recovery making the fibers switch to the hydrophilic type due to the presence hydroxide or biological sludge

1.1.2 Origin, nature and characteristics of sludge

 Origin of sludge:

- Sludge from sewerage system, canals: compositions and properties of sludge mainly are organic matter (70-82%) and some heavy metals at high levels This huge amount of sludge tends to rise

- Sludge from urban waste water treatment systems: urban wastewater including household wastewater, industrial wastewater, etc Thus, waste water is formed in the process of human activity Characteristics of urban wastewater are high organic matter content (55-65% of dirt), contains many microorganisms including pathogenic microorganisms, bacteria decompose the organic matter needed for the metabolism of contaminants in wastewater Urban waste water rich

in organic matter, nutrients, is the source for the bacteria (including pathogenic bacteria) development, is one of the main source of pollution to the water environment Urban domestic wastewater through the sewer system, is transferred

to the treatment plant and waste water drainage system of the city Sludge generated from this process as a result of the material being waste water carrying deposited in the drainage system and the activities of microorganisms in these systems, turning sand into a slurry This sludge is often contaminated with organic compounds and inorganic toxic, depending on the input waste source, so the concentration of the material in the remaining solids are the result of the wastewater treatment process

- Sludge from manholes, septic tanks;

- Sludge from aquaculture (shrimp) is the source of sedimentation into shrimp ponds, are very dangerous waste source for spread of disease problems and environmental pollution After 3-4 months, the sediment on the shrimp pond may be 20-30 cm thick covering the bottom layer of shrimp farming area Some findings ingredients of shrimp sludge showed mud components are very complex, residues and chemical materials used in shrimp farming process as lime, chemicals, sulfur deposition, alum sludge in the soil containing environmental toxins, the pathogenic bacteria in shrimp, algae and fungal pathogens and particularly decomposition products of anaerobic process as NH3, H2S, CH4, etc are factor extremely dangerous for crawfish

 The nature and characteristics of sludge

According to the study of the US Association of Civil Engineers there are at least 60,000 toxins and chemicals were found in sludge and wastewater The researchers of the US Association of Civil Engineers has determined that the sludge containing the following toxins:

- Polychlorinated biphenyls (PCBs);

- Pesticides contain chlorine including DDT, dieldrin, aldril, endril, chlordane, heptachlor, lindane, MIREX, kepne, 2,4,5-T, 2,4-D;

- The chlorinated compounds such as dioxins;

- The aromatic ring compounds;

- Heavy metal: As, Cd, Cr, Pb, Hg;

- Bacteria, viruses, protozoa, parasitic worms and fungi;

- The toxins such as asbestos, petroleum products and industrial solvents (Khai

et al, 2008)

In 2009, US-EPA published national report on sewage sludge study some features of sewage sludge as follows:

- The total solids (TS): include suspended solids and dissolved solids, usually expressed as a percentage of total solids in the slurry Total solids content depends

on the type of sludge

Typically, a liquid slurry containing 2-12% solids, while reducing slurry aqueous have solids content from 12-40% solids (including chemical additives) Dry or composting sludge solids are usually over 50%

- The volatile solids content: This is the organic compound evaporates when heated to 5500C mud in oxidizing conditions, usually expressed as a percentage of volatile solids in the slurry Most types of sludge containing 75-85% volatile solids

on a dry weight

- pH: pH affects the absorption of heavy metals in soil and plants Sludge has low pH (<6.5) promotes the absorption of heavy metals, while high pH (> 11) to kill bacteria, combining soils have neutral pH or high pH can inhibit absorption of heavy metals through the soil

- Organic matter (OM): content of organic material in the sludge is high, so can be used to improve soil physical properties (eg increased water holding capacity) Increase organic matter content will reduce the density, enhance the ability of water detention and promoting greater water infiltration (Hai, 2007)

- Nutrients: Nutrients in the sludge as nitrogen, phosphorus and potassium are

essential for plant growth High nutrient content can lead to pollution of groundwater and surface water

Nutrient contents commonly found in sewage sludge in some countries in the world are given in Table 1.1 (Hung, 2014)

Table 1.1 Nutrient contents in sewage sludge

- Metal: Heavy metal composition is easily absorbed on the surface of organic and inorganic suspended matter When these substances settles form a slurry the heavy metals will also accumulate in the mud Some heavy metals (Fe, Zn, Mn, Cu, Mo, Co, etc) are the trace element indispensable for the organism in the process of metabolism, but some metals other (Hg, Pb) is toxic Other metals such as Ca, Si, Ni, Se, are necessary for the assimilation

of the tree, but not necessary for other organisms (Hung, 2014)

Research results on the characteristics of the sludge in Indiana (USA) showed that the sludge contains about 50% organic compounds and 1-4%

inorganic carbon organic N and inorganic P are composed mainly of N and P

in the mud Organic and inorganic carbon present relatively stable during the sampling period However, the biggest fluctuation is component of heavy metals such as Cd, Zn, Cu, Ni, Pb in sludge (Sommers et al, 1976)

1.1.3 Regulations and standards on sludge

1.1.3.1 In the world

 Regulation of US - EPA

US EPA's regulations (Title 40 of the Code of Federal Regulations (CFR, Part 503) for sludge used for the purpose as applied to agriculture, landfill or incineration is defined in detail in Table 1.2 (Silveira et al, 2003)

Table 1.2 Regulations of US - EPA for some heavy metals in the sludge

according to intended use

 Regulation of European Union

- For organic compounds:

Organic matter content applied to agricultural land for sludge in each country are different rules in Table 1.3 (Khai et al, 2008)

Table 1.3 The content of organic compounds for sludge applied to

agriculture of some countries

Unit: mg/kg

adsorbable organic halogen

Di (2-ethylhexyl)phthalates (DEHP) 100 1300 - -

Polycyclic aromatic hydrocarbons

* Unit: mg/kg TEQ (Toxic equivalent quantity)

- For heavy metals: In some countries prohibit the reuse of sludge for agricultural purposes if the concentration of heavy metals exceeding the prescribed permit is given in Table 1.4 ((Khai et al, 2008)

Table 1.4 Heavy metal content to apply sewage sludge in agriculture in

Table 1.5 Limit values of some microorganisms in sludge as standard in

some countries in the world

Poland Sludge is not used if the contain

Denmark Sludge is not used if the contain

Salmonella Streptococcal < 100/g

1.1.3.2 In Viet Nam

Vietnam issued a national technical regulation on hazardous waste threshold QCVN 07: 2009/BTNMT, including regulations applicable to sewage sludge Currently, private standards QCVN 50: 2013/BTNMT were issued according to Circular 32/2013 / TT-BTNMT, dated 25.10.2013 of the Minister of Natural Resources and Environment, based on QCVN 07: 2009/BTNMT, regulation of hazardous threshold of parameters (except radiation parameters) in sewage sludge generated from the wastewater treatment process, as the basis to classify and manage sludge

According QCVN 50: 2013/BTNMT, sludge from the wastewater treatment process are defined as hazardous waste if it is one of the following cases:

- pH ≥ 12.5 or pH ≤ 2.0

- In sludge samples analyzed at least 1 parameters specified in Table 1.6 have simultaneous value exceeded the absolute content (Htc) and hazardous threshold (Ctc)

Value absolute content threshold (Htc, ppm) is calculated by the following formula:

Htc = (1) Which:

+ H (ppm) is value of absolute content specified in Table 1.6;

+ T is the ratio of the volume of dry solid components in sewage sludge samples with a total sample volume of sludge

Hazardous threshold calculated according leaching concentration of parameters in the sludge from the water treatment process is specified in Table 1.6

Table 1.6 Basis absolute content (H) and hazard threshold calculated according leaching concentration (Ctc) of the parameters in the sludge

formula

Basis absolute content H (ppm)

Hazardous threshold calculated according leaching concentration Ctc (mg/l)

1.1 4 The impact of the sludge on the environment and human health

Sludge is determined by US-EPA as a pollutant In 2011, US-EPA research at the National Research Council of the USA (NRC) to determine the risk to the health

of humans and animals caused by sludge In this document, the NRC has indicated that many of the dangers of mud unclear or not interested satisfactory, especially urban sewage sludge used as a utility fertilizer or wastewater from urban waste water polluted to be used as an irrigation source

The sludge contains pathogenic bacteria, viruses and protozoa with other parasitic worms may increase the potential risk to the health of humans, animals and

plants Additional fresh slurry into the soil causing E coli bacteria levels rise

significantly greater value (Unc et al, 2006) According to the World Health Organization-WHO (1981), report on the risks to health identified pathogenic microorganisms mainly Salmonella and Taenia is the biggest concern

Sludge from the wastewater treatment plant is handled through the complex process of reducing pollution levels, but does not remove all pathogens are hazardous substances of ingredients such as PAHs, PCBs, dioxins, heavy metals Other studies conclude that plants absorb large amounts of metals and toxic pollutants stored products, which are then consumed by humans (Turek et al, 2005) Sludge impact on human health can be divided into influence seen immediately after exposure (such as smell, infection by breathing/swallowing bacteria) or arising from long-term exposure (exposure metal emissions from sludge treatment process), influence gradually, not immediately see the consequences These people risk being affected most frequently had contact with sludge as sewage

staff, sludge dredging workers, workers at composting facilities, farmers cultivating the land from waste mud and household (Silveira et al, 2003)

In Vietnam, there is currently no specific statistics about the harmful effects of sludge on the environment However, in practice the large amount of sludge are dredged from the sewer system, septic tanks, lakes and sludge from water treatment plants, etc, discharged serious consequences The sludge from the drainage system and from the wastewater treatment plant is pre-treated or untreated, transported to landfills or dumped at locations not identified, affecting to environment around, polluting the air and leaching pollute groundwater and surface water leading to reduced water quality

The composition and properties of sludge have important implications in the study of the ability to leverage the mud for different purposes (used as fertilizer, agricultural land reclamation, leveling, production of building materials, etc), it also allows us to identify the cause of accumulation of pollutants in the mud of a canal and distributed toxic pollution in mud Therefore, the potential impact of the sludge

on the environment may be mentioned include:

- Pollute ground water: In the mud dredging component containing a relatively large amount of water, the dry season is not enough water to permeate to groundwater and easily evaporate However, during the rainy season can blend these hazardous substances in sludge and leached into the ground water, causing groundwater pollution

- Surface water pollution: Between sediment environment and water environment have a certain balance, when properties of environment change, pollutants accumulate in sediment can blend back in water lead to water pollution

- Air pollutants: The process of anaerobic decomposition of sludge will generate gas smells like H2S, CH4, NH3, etc cause the greenhouse effect and influence to people

- Soil pollution: Soil pollution is mainly caused by the harmful ingredients in sludge with high concentrations, including organic chemicals, heavy metals and difficult to degrade substances such as nylon bags, iron cans in sludge dredging would pollute the soil and hard to overcome

- Impact on the ecosystem: Losing urban aesthetic, affecting aquatic life in water

- Impact on animal: Sludge is also the habitat of thousands of organisms, microorganisms, etc and through the food chain that sludge could affect higher animals including humans, especially sludge contains heavy metals

Heavy metal content in sludge is the first concern when dredging canals, which are closely related to the purpose of reusing sludge or sludge poured impacts incorrectly defined as affecting the ecosystem in beach area pour sludge Heavy metal composition is easily absorbed on the surface of organic and inorganic suspended matter When these substances forming sediment settles, the heavy metals will also accumulate in sludge Some heavy metals are microelements are indispensable to the organism in the process of metabolism, however some other heavy metals are toxic There are six basic elements (Fe, Zn, Mn, Cu, Mo, Co) are called micronutrients nutrients needed for plants Other metals such as Ca, Si, Ni,

Se, Al necessary for the assimilation process of the plant but is not necessary for other organisms Hg and Pb for the metal components are completely unnecessary for plants, microorganisms and causing toxins to humans (Silveira et al, 2003)

1.2 The sludge treatment method

1.2.1 Handling by incineration

Incineration method is fairly common method in the world today for handling solid waste in general, especially hazardous waste and industrial sludge This is the most thorough treatment than other methods

Incineration is the period of high temperature oxidation in the presence of oxygen in the air, hazardous waste components are converted into gases and unburned components (ash, slag)

Advantage of incineration method is thoroughly treated pollution indicators of solid waste, minimize solids for final processing of the curing or reuse of ash However, investment costs, the cost of energy consumption is very high and higher processing costs

1.2.2 Handling by landfilling method

Landfilling is the common method and the simplest of handling solid waste Sanitary landfill is a method of destruction of biological control parameters of environmental quality (odor, air, leachate) during decomposition

The advantage of this method is that investment costs for landfilling processing are not large Sludge from the electronics industry could also buried along with sludge arising from other sectors

The downside of this method is that the landfill covers a large area, the time of decompose are slow and pollute the surrounding area

Currently, in Vietnam, the sludge landfill usually openings landfills, polluting the environment and aesthetic

1.2.3 Handling by composting biological method

Composting is process of biological stabilization of organic matter to form humus waste Annealing process conducted by two methods: anaerobic composting and aerobic composting (forced air blowing) The waste composting with ingredients mainly organic substances are biodegradable For less concentrated sludge source, they may apply this method, due to sludge contains organic matter the However, for particular industrial sludge containing heavy metals as inappropriate

- Anaerobic decomposition:

This is the method of sludge stabilization and can reduce volume, stable sludge properties This method also has the potential to reduce the amount of pathogenic organisms in the sludge The process of decomposing in anaerobic decomposing systems can be divided into several steps The process of anaerobic digestion of sludge takes place in the long and total of temperature are relatively stable, typically at 350C in 20 days to show results in disinfection and create the optimal amount of methane Anaerobic degradation technology can acquire large amounts of methane, however, a long time requires to install, build large treatment tank system, the waste of the system still requires suitable treatment technologies like landfill, solidification or reused as fertilizer

- Aerobic decomposition:

The process of decomposition occurs by aerobic microorganisms involved decomposing organic matter and generate heat Temperature of the decomposition system can be up to 700C Typically, for aerobic treatment of sludge, temperature can reach 50-650C after 5-6 days, so the pathogenic bacteria will be killed The

operating costs for aerobic treatment would be higher 5-10 times the anaerobic degradation system but time is shortened Similar anaerobic degradation technology, waste after aerobic decomposition process still requires appropriate technologies like landfill, solidification or reused as fertilizer

1.2.4 Handling by recycling method

Recycling activity is recovered from waste components can be used to transform into new products, or other forms of energy in service activities production activities Recovery and recycling of waste is one of the methods to solve the problem of environmental pollution In Vietnam, the hazardous waste disposal regulations mainly waste discharge curing method, landfilling, incineration (about 50% of the total solid waste generated is treated by landfilling uncontrolled) The proportion of solid waste is recovered and reused is 17-25% However, in some countries in the world, the proportion of recycling and recovery is very high, over 40% Recycling activities bring greater economic efficiency, saving natural resources by replacing the original raw materials, reduce waste, reduce environmental pollution, reduce processing costs, reduce the area for landfills Some developing countries in the world have developed trend waste recycling become environmental industry

1.3 Management situation of urban sludge in the world and in vietnam

1.3.1 Sludge management in the world

The management and sludge treatment methods in the world are listed in Table 1.7 (Inglezakis et al)