WQ in Aquaculture

8/13/2019 WQ in Aquaculture

1/35

SQ10403SQ10403

Water quality in AquacultureWater quality in Aquaculture

Basic differences between freshwater andseawater

Types of water quality problems

Water quality management for aquaculture


2/35

Differences in Freshwater and Marine/Estuarine water

1. Concentration of dissolved gases at saturation:

As the dissolved salt concentration increases in water,the solubility of dissolved gases at saturation declines.

For example, at 25oC and sea level, freshwater contains8.24mg/L dissolved oxygen at saturation.

The corresponding value for water with 20ppt salinity at25oC and sea level is 7.36mg/L.

This is because a greater amount of water is bound toions and unavailable to dissolved gases in estuariesthan in freshwater.


3/35

2. Sedimentation:

Suspended soil particles will settle from brackish waterfaster than from freshwater because of the higherconcentration of ions in estuaries.

3. Effects of activities of chemical substances:

Ion uptake by plants and animals are related to activitiesrather than total concentrations.

Increased salinity of water decreases activity coefficients.

Greater total concentration of a particular substance isnecessary to provide a given activity of that substance inestuarine water than freshwater.


4/35

4. Reacts to dissolved metals:

Metallic ions have a greater tendency to formheterogeneous equilibrium with oxides, hydroxides,carbonates and sulfates in estuaries than freshwater.

Ionic forms of metals are more active chemically andphysiologically than complex forms. Therefore, ions ofheavy metals are generally less toxic in estuaries thanin freshwater.

5. Liming:

Brackish water normally contains a high total hardnessand total alkalinity

No needs to lime in estuaries system.


5/35

6. Buffer capacity:

Estuaries normally have pH above 7.5 (Marine above 8.0),

because of high alkalinity and it is well buffered againstdrastic changes in pH. Freshwater always shows widefluctuation in pH

7. Effects of fertilizer:

Blue green algae do not grow as well as in estuaries ormarine habitat as in freshwater system.

Nitrogen fixation of blue green algae is a major source ofnitrogen in freshwater ponds.

Nitrogen fertilizer is more important in brackish/marinewater than freshwater.

Phosphorus apparently is equally important in both watersystems


6/35

8. Hydrogen sulfide:

Estuaries contains a high concentration of sulfates. So,

hydrogen sulfide production in anaerobic mud is a greaterproblem in brackish water than in freshwater.

9. Phytoplankton communities:

Salinity above 10 or 15ppt phytoplankton communitiesare comprised mainly of diatoms and green algae; bluegreen algae seldom are abundant. Freshwater alwayshave dense blooms of blue green algae.

10. Corrosion:

Estuaries/marine water is generally more corrosive thanfreshwater because of salinity.


7/35

Types of Water Quality Problems

Basically there are three types of water quality problems:

1. Involvement of natural quality of water at a particularsite.

Examples of such are: high turbidity in supply water , acidsoil and water, low or high salinity, alkaline water, highconcentrations of iron in water supply and high

concentration of hummus substances.

These problems can be avoided during selection of water sourcesand also by doing treatment.


8/35

2. Events that develop in system:

Sometimes natural productivity is not sufficient andmust have to supplement nutrients like fertilizer orexcess feed.

High feeding rates can lead excessive growth ofphytoplankton, dissolved oxygen depleted and toxicconcentrations of metabolites increases.

Due to excessive growth of phytoplankton, highrates of photosynthesis may result in excessive pHor gas super saturation and cause thermal andchemical stratification.


9/35

3. Pollutants:

May enter directly from human induced materials.Feed waste or pollution causes by surroundingdevelopment: Use of trash fish together with feedingredients can pollute the water.

A river, which supplies water to estuaries or in anyaquaculture production system may be polluted by avariety of municipal, industrial and agriculturaleffluents.

Besides all these basic problems, soil is considered as animportant factor controlling water quality


10/35

Water Quality Management forWater Quality Management for

AquacultureAquaculture

Water quality management for aquaculture essentiallyWater quality management for aquaculture essentiallyforfor::

1. Supply of nutrients for primary production1. Supply of nutrients for primary production

e.g. liming and fertilization (Inorganic or organic)e.g. liming and fertilization (Inorganic or organic)

2. Reduced physiological stress in aquatic organisms by2. Reduced physiological stress in aquatic organisms by

-- Increase 0Increase 022-- Reduced HReduced H22S, CHS, CH44-- Sudden changes of salini ty, temperature and pHSudden changes of salini ty, temperature and pH

3. Maintain healthy condition in aquatic animals3. Maintain healthy condition in aquatic animals

-- Prevent diseases and microbial balancePrevent diseases and microbial balance

--Uptake of heavy metalsUptake of heavy metals


11/35

Effects of liming on water qualityEffects of liming on water quality

Lime is important to maintain the water quality in uniqueLime is important to maintain the water quality in uniquecondition.condition.

The advantages of using lime are as follows:The advantages of using lime are as follows:

1. Lime increases the pH of water and improved1. Lime increases the pH of water and improvedsurvival, increase reproduction and growth ofsurvival, increase reproduction and growth ofaquaculture lifeaquaculture life

2. Lime increases the pH of bottom mud and helps in2. Lime increases the pH of bottom mud and helps in

mineralization process to release nutr ients formineralization process to release nutrients forprimaryprimary producers e.g. it increases availability of phosphorusproducers e.g. it increases availability of phosphorus


12/35

3. Supply calcium necessary fordevelopment of exoskeleton of aquaticanimals

4. Increase benthic production infertilized pond

5. Increase microbial activity in mud.Greater microbial actively diminishesthe accumulations of organic matter inbottom mud and favor recycling ofnutrients.

6. Lime increase the alkalinity of waterand increases the availability of CO2photosynthesis.


13/35

7. Lime may be cleared of humic strains ofvegetative origin, which restrict lightpenetration

8. Inorganic fertilizer fails to produced

adequate phytoplankton bloom, but withthe addition of lime bloom maydeveloped

9. Lime is important for extremely acidic

soils (Acid Sulfate Soil).


14/35

Liming materials

1. CaCO3 (Calcite)

CaCO3 + 2H+ Ca2+ + H2O + CO2

2. Ca Mg(CO3)2 as dolomite

Ca Mg(CO3)2 + 4H+ Ca2+ + Mg2+ + 2H2O + 2CO2

3. Ca(OH)2 (Calcium hydro oxide)

Ca(OH)2 + 2H+ Ca

2+

+ 2H2O

4. CaO (Calcium oxide)

CaO + 2H+ Ca2+ + H2O


15/35

Calcium containing compounds that do not

neutralize acidity are not l iming material.

Not all calcium product can supply Ca2+ in water.

Agricultural gypsum (CaSO4) is good source of

Ca2+ but SO4 cannot neutralize acidity.


16/35

Soil is considered as an important factor controlling water quality.

Acid Sulfate Soil (example)

Specially developed in brackishwater marshes containiron pyrite and becomes extremely acidic.

Such soil called potential acid sulfate soil or catsclay.

Formation of acid sulfate soil is regular process inbrackishwater.

River and run off carrying heavy loads of sediments and

deposited near shore.

Low water level and vegetation becomes established and aswam forest developed.


17/35

In swam forest, tree root trapped organic and

inorganic debris

Decomposition in dense masses of organic

debris resulted in anaerobic conditions

Sulfur-reduction bacteria becomes abundant,Sulfides produced by bacteria accumulated in

pore spaces mud as H2S

H2S combine with forest iron to form

precipitates of iron sulfide.

Iron sulfide under went further chemical

reaction to form iron di-sulfide that crystallize

to form iron pyrite.


18/35

The overall reactions may be summarized as:The overall reactions may be summarized as:

2CH2CH22O (Organic matter) + SOO (Organic matter) + SO4422-- HH22S + 2HCOS + 2HCO33

--

Fe (OH)Fe (OH)22 + H+ H22SS FeSFeS + 2H+ 2H22OO

FeSFeS + S+ S FeSFeS22 (Pyrite)(Pyrite)

As long as soils containing pyrites are submerged andAs long as soils containing pyrites are submerged and

anaerobic, they remain reduced and change littleanaerobic, they remain reduced and change lit tle


19/35

If water drained and exposed to air, oxidation occurs andIf water drained and exposed to air, oxidation occurs andsulfuric acids forms according to the following equations:sulfuric acids forms according to the following equations:

FeSFeS22 + H+ H22O + 3.5 OO + 3.5 O22 FeSOFeSO44 + H+ H22SOSO44

2FeSO2FeSO44 + 0.05 O+ 0.05 O22 + H+ H22SOSO44 FeFe22(SO(SO44))33 + H+ H22OO

FeSFeS22 + 7Fe+ 7Fe22(SO(SO44))33 + 8H+ 8H22OO 15FeSO15FeSO44 + 8H+ 8H22SOSO44

The production of ferric sulfate from ferrous sulfate isThe production of ferric sulfate from ferrous sulfate is

accelerated by the bacterial activity, specially genusaccelerated by the bacterial activi ty, specially genus

ThiobacillusThiobacillus and under acidic condit ions, the oxidation ofand under acidic conditions, the oxidation of

pyrites by ferric sulfate is very rapidpyrites by ferric sulfate is very rapid


20/35

In addition, ferric sulfate may hydrolyze according toIn addition, ferric sulfate may hydrolyze according to

the following reactions:the following reactions:

FeFe22(SO(SO44))33 + 6H+ 6H22OO 2Fe(OH)2Fe(OH)33 + 3H+ 3H22SOSO44

FeFe22(SO(SO44))33 + 2H+ 2H22OO 2Fe(OH)(SO2Fe(OH)(SO44) + H) + H22SOSO44

Ferric sulfate also react with iron pyrite to fromFerric sulfate also react with iron pyrite to from

elemental sulfur and the sulfur may be oxidized toelemental sulfur and the sulfur may be oxidized to

sulfuric acid by microorganisms:sulfuric acid by microorganisms:

FeFe22(SO(SO44))33 + FeS+ FeS22 3FeSO3FeSO44 + 2S+ 2SOO

SSOO + 1.5 O+ 1.5 O22 + H+ H22OO HH22SOSO44


21/35

Sulfuric acid dissolves aluminum, manganese, zinc andSulfuric acid dissolves aluminum, manganese, zinc and

copper from soil and runoff from acidcopper from soil and runoff from acid--sulfate soils or minesulfate soils or mine

spoi ls not only is highly acidic, but it may contain potentiallyspoils not only is highly acidic, but it may contain potentiallytoxic metallic ions.toxic metallic ions.

A potential acidA potential acid--sulfate soil will have high total sulfursulfate soil will have high total sulfur

contents (more than 0.75%) and lower pH (less than 3.5)contents (more than 0.75%) and lower pH (less than 3.5)

Ferric hydroxide can react with absorbed bases, such asFerric hydroxide can react with absorbed bases, such as

potassium in acid sulfate soils, to formpotassium in acid sulfate soils, to form JarositeJarosite, a basic iron, a basic iron

sulfate:sulfate:

3Fe(OH)3Fe(OH)33 + 2SO+ 2SO4422-- + K+ K++ + 3H+ 3H++ KFeKFe33(SO(SO44))22(OH)(OH)66. 2H. 2H22O + HO + H22OO


22/35

Oxidation in acid soil is partly chemical and partly biological,

as seen in the following sequences:

2FeS2 + 2H2O + 7O2Chem or Bio 2Fe2+ + 4H+ + 4SO4

2-

2Fe2+ + O2 + 4H+ Chem or Bio 2Fe3+ + 2H2O

2Fe3+ + FeS2Chemical 3Fe2+ + 2SO

2SO + 3O2 + 2H2O Biological 4H+ + 2SO42-


23/35

Chemical Fertilizer

Chemical compounds used as fertilizer are same toones used to fertilize agricultural crops.

NPK is common primary nutrients found infertilizer. They are present in reactively simplecompounds, which ionizes to give NO3, NH4

+,H2PO4, HPO4

2- or K+

Ca, Mg, S uses as secondary nutrients, applywhenever nutrients are limited.

Trace nutrients- Cu, Zn , br, Mn, Fe and molybedumalso added to some fertilizer.


24/35

PhosphorusPhosphorus

PhosphorusPhosphorus is key metabolic nutrients and supply regulates theis key metabolic nutrients and supply regulates the

productivity of natural water.productivity of natural water.

Qualitative model of phosphorus cycle in fish pond

Life span of phytoplankton is 1-2weeks. So, dead phytoplanktonreleased phosphorus quickly bymicrobial degradation. Large

part release to the water bydecay before cells settles tobottom.

Mud containing organicphosphorus microbialdecomposition of organic matterwill release ortho-phosphoruswhich precipitated by variousions of aluminum calciumcompounds.


25/35

Phosphorus available in water as soluble or ortho-phosphate ions, which may consider as ionizationproduct of ortho-phosphoric acid (H3PO4)

H3PO4 H+ + H2PO4-

H2PO4- H+ + HPO42-

HPO42- H+ + PO43-


26/35

Effects of pH on the relative proportions of HEffects of pH on the relative proportions of H33POPO44, H, H22POPO44--,,

HPOHPO4422-- and POand PO44

33--


27/35

Phosphorus can absorbed in water more than normal requirement. TPhosphorus can absorbed in water more than normal requirement. Thehe

absorption of phosphorus in excess the amount required for growtabsorption of phosphorus in excess the amount required for growthh

has been identif ied and is termed as luxury consumption.has been identif ied and is termed as luxury consumption.

Luxury consumption of phosphorus by phytoplankton


28/35

Nitrogen

Nitrogen is the key component for building protein,which is part of amino acids.

So, directly requires for the primary productivity.

Most transformations of nitrogen in the cycle arebiological.

In contrast to largely abiotic phosphorus cycle, thenitrogen cycle in ponds is regulated primarily by

biological activity


29/35

Fixation of molecularFixation of molecular

N2 from atmosphereN2 from atmosphereby biological,by biological,

meteorological, ormeteorological, or

industrial processesindustrial processes

(Free living bacteria,(Free living bacteria,

blue green algae)blue green algae)

Decomposit ion ofDecomposition of

organic matter. Mostorganic matter. Most

of organic matterof organic matterexists as aminoexists as amino

groups of proteingroups of protein

(amides & amines)(amides & amines)


30/35

Microbial activity

Proteins are breakdown into NH3-N (excretory material) bybacteria and fungi, process is called ammonification andammonia is released to the environment (minieralization) orassimilated into microbial tissue.

Ammonification is heterotrophic processes occurs either aerobicor anaerobic condition.

Ammonium nitrogen goes through nitrification process.Nitrification: Breakdown of N-containing organic compounds intoNO2 ad NO3

Oxidation of ammonium nitrogen by nitrate is done by

chemoautotrophic bacteria, primarily by Nitrosomas in the firststep uses ammonium and Nitrobacter in second step that usesnitrite.

First step: NH4+ + 1.5 O2 NO2- + 2H+ +H2O

Second step: NO2- + 0.5 O2 NO3-


31/35

In absence of molecular nitrogen, many microorganisms can usenitrate or other oxidized forms of nitrogen instead of oxygenas terminal electron acceptors in respiration.

De-nitrification is the process of reduction of NO2 and NO3 to N bymicroorganism

Pathway of nitrate respiration and de-nitrification can besummarized as

1. 2HNO3 + 4H+ 2HNO2 + 2H2O

2. 2HNO2 + 4H+ N2O2H2 + 2H2O

3a. N2O2H2 + NH+ 2HH2OH

2NH2OH + 4H+ 2NH3 + 2H2O

3b. N2O2H2 + 2H+ N2 + 2H2O

3c. N2O2H2 N2O + H2ON2O + 2H

+ N2 + H2O


32/35

Forms of nitrogen in water

Inorganic form:

NH3-N, NH4, NO2 and NO3

Low dissolved oxygen tends to increase NO2

Inorganic nitrogen increases in unpolluted water

NH3 is more toxic, specially un-ionized from of NH3

Ammonia is more toxic than NH4

Nitrogen also present in soluble organic compounds as:

- living particulate organic matter and- dead particulate organic matter.


33/35

Nitrogen as fertilizer

Most common inorganic form of nitrogen fertilizers are:

- Anhydras ammonia- Ammonium Nitrate (33-35% N)

- Ammonium sulfate (20-22% N)- Ammonium phosphate- Di-ammonium phosphate (18% N)- Sodium nitrate (16% N)- Potasium nitrate (13% N)- Urea (45% N)

- Ammonia polyphosphate- Calcium nitrate (15% N)


34/35

Organic fertilizer that uses as nitrogen sources are:

- Cow dung- Poultry drop- Sheep & swine drop

- Seed meals- Leaf waste- Kitchen waste- Compost


35/35

Composition (%)

Types of manure

Moisture Nitrogen P2

O5

K2

O

Cow dung 85 0.5-0.7 0.2-0.5 0.5

Poultry drop 72 1.2 1.3 0.6

Swine 82 0.5 0.3 0.4

Sheep 77 1.4 0.5 1.2

Leaf waste 74-90 0.21-0.45 0.09-0.16 0.54-1.24

Soybean mealCotton seed 9.77.2 7.316.93 1.442.45 1.742.30

Mixed grass dry 11 1.12 0.48 1.44

Rice straw 7.2 0.56 0.21 1.08

Fertilizer constituents in fresh manure of selected farm animalsFertilizer constituents in fresh manure of selected farm animals

Date post:	03-Jun-2018
Category:	Documents
Upload:	jasumin91
View:	224 times
Download:	0 times

WQ in Aquaculture

Documents