Two lab experiments to be just in one reportEnvironmental Engineering Laboratory (Wastewater treatment)Coordinator: (Sathaa) Arumugam Sathasivan
Contact detail:
Sathaa: (02-47360941, a.sathasivan@ westernsydney.edu.au)
Shashika:([email protected]),Dileepa:(Dileepa.Rathnayake@ westernsydney.edu.au), Upul :[email protected]
Welcome to this interactive experiment in which you can learn about the conventional wastewater treatment processes and plot out the data obtained during activated sludge treatment process.Tasks
You will do mainly three exercises as detailed below:
o Exercise 1 involves measuring the dissolved oxygen (DO) in wastewater every 3 inutes after introducing organic carbon (acetate) into the water samples.
o Exercise 2 involves calculation of carbon removal during activated sludge treatment process and compare this result with actual DOC removal.
o Exercise 3 involves measuring the heavy metal levels in treated drinking water and treated wastewater
Typical conventional wastewater treatment process for organic carbon removalPrimary Treatment
The primary treatment involves three different steps; Screening, Grit Removal and Sedimentation. Screening is employed to remove objects that are large enough to be caught in a series of screens. This is followed by grit removal especially for the removal of dense material such as sand, dirt, or broken glass. Afterwards, it is sent through primary sedimentation tanks to settle sludge while grease and oils rise to the surface are skimmed off.Secondary Treatment (Activated Sludge Process)
The primary treated wastewater is blended with the microbiological biomass, to form mixed liquor in an aeration tank. The diffused air is applied to provide oxygen for the microbiological process that breaks down the organic compounds in the primary treated wastewater. Then, biologically active sludge that settles in these tanks is continually removed and returned to the aeration tanks to sustain microbiological population there and the overflow from the sedimentation tanks is the final treated secondary wastewater. The general arrangement of an activated sludge process for removing carbonaceous compounds includes following items.1. Aeration tank where oxygen is diffused into the biomass
2. Sedimentation tank to allow the biomass to settle
Fig 1: Flow Chart of Wastewater Treatment Plant (Beenyup Wastewater Treatment Plant)The overall goal of the activated-sludge process is to remove substances that have a demand for oxygen from the system. This is usually accomplished by the biochemical processes mediated by the microorganisms. To achieve high activities of microorganisms following steps need to be taken.
Supply of sufficient amount of oxygen
Maintenance of appropriate water temperature
pH adjustment
Agitation to increase the opportunity for contacting microorganisms, substrate and oxygen
Addition of nutrientsThe conversion of organic matter to gaseous end products and cell tissue can be accomplished aerobically (in the presence of oxygen). A portion of the organic material is oxidized to end products. This process is carried out to obtain the energy necessary for the synthesis of new cell tissue. In the absence of organic matter, the cell tissue will be endogenously respired to gaseous end products and a residual to obtain energy for maintenance. In most biological treatment systems, these three processes occur simultaneously. Stoichiometrically, three processes as follows represent for an aerobic process (oxygen demand):Oxidation process:COHNS (organic matter)+ O2 + bacteria CO2 + NH3 + other end products + energySynthesis:COHNS + O2 + bacteria + energy C5H7NO2 (new bacterial cells)Endogenous respiration:-
C5H7NO2 + 5O2 5CO2 + NH3 + 2H2O + energy
Tertiary Treatment (Nutrient Removal)
The secondary effluent still contains a high level of nutrients such as dissolve organic carbon, nitrogen and phosphorous that eventually leads to the eutrophication. This provides a platform for the growth of weeds, algae and cyanobacteria resulting into algal boom.
Objectives
The major objective of this experiment is to achieve fundamental knowledge of convectional wastewater treatment particularly activated sludge process. This will be done by examining the improvement in wastewater quality through synthetic wastewater experiments in the laboratory using following steps.o Measuring selected heavy metal levels of treated drinking water and wastewater samples
o Measuring DOC levels of synthetic wastewater before and after the experiment.
o Measuring ammonia, nitrite, nitrate and phosphorous levels of synthetic wastewater before and after the experiment
o Measuring DO of original synthetic wastewater immediately after aeration
o Tracking DO continuously in fixed time interval
o Calculation of carbon removal resulted due to DO consumption and compare the calculated value with the actual DOC removal
Experimental procedure
1. Prepare synthetic wastewater by maintaining carbon, nitrogen and phosphorous ratio of 100:15:1
2. Mix synthetic wastewater with biomass collected form wastewater treatment plant
3. Supply oxygen and maintain temperature at 24C to enhance microbial activities
4. Then measure the DO of the sample continuously by putting it into air tight container.
5. Calculate the respective carbon removal using the following equationC6H12O6 + 6O2 6CO2 + 6H2OFor example, carbon consumption during 1mg/L DO depletion can be calculated using above equation as follows;32 6mg/L oxygen is required to remove 12 6mg/L carbon
i,e. 192mg/L oxygen is required to consume 72mg/L Carbon
1mg/L oxygen is required to consume 72/192 = 0.375mg/L carbonThus, this equation can be used to calculate carbon consumption for all residual DO in synthetic wastewater tracked during the experiment.6. Measure the heavy metal levels in treated drinking water and wastewater samples and identify the deference.
7. Measure ammonia, nitrite, nitrate and phosphorous levels of treated drinking water and wastewater samples and identify the deference.
8. Measure the DOC level of synthetic wastewater before and after the experiment.
Report and Analysis
The following should be included in the report.
Discussion on result obtained from the experiment and the related calculations
Graphical presentation to explain your lab result
ConclusionsTable 1: DO and Carbon Consumption
Time (minutes) DO(mg/L) Carbon Removal (mg/L) Remarks
03691215182124273033363942454851545760
Environmental Engineering : Water Treatment Processes
Coordinator: A/Prof. Arumugam Sathasivan (Sathaa)
Contact details:
Coordinator: (Sathaa) Arumugam Sathasivan
Contact detail:
Sathaa: (02-47360941, a.sathasivan@ westernsydney.edu.au)
Shashika:([email protected]),Dileepa:(Dileepa.Rathnayake@ westernsydney.edu.au), Upul :[email protected]
Welcome to this interactive experiment in which you will learn about the conventional water treatment processes and plot out the data obtained at various stage of the experiment for practical purposes.
Tasks
You will do exercises 1, 2, 3 and 4 as detailed below:
1. Exercise 1 involves measuring the parameters of raw water sample, which include turbidity, colour, DOC and UV absorbance (UV254).
2. Exercise 2 involves measuring the parameters of original sample after leaving intact for half an hour to allow for settlement.
3. Exercise 3 involves simple Jar test to demonstrate turbidity removal by coagulant and measurement of parameters of purified water.
4. Exercise 4 involves dosing chlorine into treated and untreated samples and monitor chlorine decay in different samples for first 2 hours.
5. Exercise 5 involves measuring THM (Trihalomethane) level after addition of chlorine and compare with a water sample without chlorine.Conventional Water Treatment ProcessBackground and parameters definition
Natural waters are rarely of satisfactory quality for human consumption or industrial use and often require appropriate treatment. Figure 1 illustrates the conventional water treatment process. Such process depends on raw water quality and the purposes of usage. Natural raw water usually has impurities quantified by colour, turbidity, odour and taste. These are called organoleptic parameters. It also may contain excessive disinfection by products (DBPs) precursors, which are quantified by dissolve organic carbon (DOC) or UV absorbance. During the laboratory experiment, a conventional domestic water treatment process will be undertaken. Water quality related parameters listed as follows will be measured in order to understand the necessity and effectiveness of water treatment.
Figure 1: Conventional Water Treatment
Source: http://www.sawater.com.au/SAWater/Education/OurWaterSystems/Water+Treatment+Plants.htmColour
Colour in water means that the water absorbs light in the visible spectral range (400 to 700 nm). The ideally pure water is colourless. Colour in water is caused by dissolved minerals, dyes or humic acids from plants/animals. The later causes a brown-yellow unsightly colour. Colour is measured in units of mg/L (Pt/Co). The colour of drinking water should be maintained below 3 mg/L (Pt/Co). The colour can also be measured using UV absorbance. In this experiment, the colour is measured using HACH R2800 spectrophotometer.Turbidity
Turbidity is due to the presence of particulate matter and is a measure of the ability of water to scatter light. It is caused by the presence of very fine suspended or clay particles. Turbidity is measured in nephelometric turbidity units (NTU). The turbidity of drinking water is required less than 0.1NTU (to control possible contamination from Giardia and Cryptosporidium cysts). Turbidity is sometimes described as the cloudiness of water. In this experiment, water turbidity is measured using HACH2100 Turbidimeter.UV Absorbance (UV254)
Dissolved organic compounds with aromatic structures absorb UV-light. Thus, the measurement of UV absorption is an indication for the pollution of water with such substances. In surface and drinking water technology this method has a long tradition. In addition UV-absorption has a very good correlation with DOC. So, UV some time also used as surrogate parameter for DOC. They are usually produced by natural organic matters (NOM) existing in most surface or ground water bodies. DOC is believed to cause many issues in drinking water supply systems such as consuming chlorine, discoloration, encouraging microbial growth etc.Disinfection by-products:
DOC is believed to be a source of DBPs precursors, which can react with chlorine during disinfection process and consequently produce trihalomethane (THM) and halo acetic acid (HAA). Both THM and HAA are promulgated as producing adverse impacts on human health. In this experiment, UV254 is measured by UV spectrophotometer to see the effect of treatment in organic carbon.
Objectives
The major objective of this experiment is to achieve fundamental knowledge of conventional water treatment processes and their effects on water quality through bulk water experiments in the laboratory.
Measuring the parameters of raw water and purified water
Manipulating the various physical and chemical treatment process
Dosing and monitoring chlorine decay in all target samples
Understanding the impact of chlorine on disinfection by-products formation.Report and Analysis
Your report (Bound hard copy with Turnitin report) should be submitted to assignment office on the 21st of October. The usual penalties apply for late submission. The following should be included in the report. Discussion on result obtained from four different exercises and compare the result against the raw water and hence to identify most effective dose on terms of turbidity,DOC, colour and UV removal
Discussion on the total chlorine decay profiles obtained from raw and treated waters
Graphical presentation to explain your lab result
ConclusionsExperimental procedure1. First, check the Colour, Turbidity, DOC and UV254 of original sample.
2. Then keep original water sample for half an hour for sedimentation of suspended solids.
3. After half an hour, test for colour, turbidity and UV254 in original sample and compare them with the one before sedimentation.
4. To settle fine particles, add a variable FeCl3 (Table 1) and maintain constant pH into original water and mix it using Jar Test. Mixing speed is made 200 rpm for the first 2 mins and controlled at 20 rpm for another 20 min. After coagulation, leave the sample intact until most flocs are settled. Then, filter the water through a prewashed 0.45m CA filter and test all three parameters of the filtrate.
5. Dose chlorine (2.0mg/L as Cl2) into all target samples (Milli-Q water, Raw water and purified water). Monitor the chlorine decay in all samples intermittently.
6. Measure THM (Trihalomethane) using Gas Chromatography (GC).
Fig 2: Experimental Flow Chart for Water Treatment in Laboratory ExperimentResults for reportTable 1: Water quality assessment
Stage Turbidity (NTU) UV254_10cm DOC Colour (Pt/Co) Remarks
Original SampleTable 2: Optimum dose of ferric chlorideFeCl3.6H2O (mg/L) 5 10 25 50
Turbidity (NTU)
Colour (Pt/Co))
DOC
UV254_10cmTable 3: Chlorine decay characteristics for raw water
Date Time Total chlorine (mg-Cl2/L)
Remarks
MQ Raw water 5 mg/L FeCl3 10 mg/L FeCl3 25 mg/L FeCl3 50 mg/L FeCl3Table 4: THM levels in treated, raw and MQ waterDate THM
Remarks
Before Chlorine decay test for 50 mg/L FeCl3 added sample After Chlorine decay test for 50 mg/L FeCl3 added sample