Standard Six-Paddle Programmable Jar Tester
Microprocessor-controlled six-station paddle mixer with digital tachometer (10 to 300 rpm) and illuminated base.
Civil Engineering / Jar Test Coagulation
FREE TO EXPLORELABORATORY 33 · CIVIL ENGINEERING
Coagulation-Flocculation Optimization & Residual Turbidity via Standard Jar Test
Determine the optimum coagulant dosage (alum / polyaluminum chloride) and rapid/slow mixing conditions for maximum turbidity and suspended colloidal particle removal from raw surface water according to ASTM D2035. Explore interactive structural mechanics, materials simulation, and civil engineering telemetry.
STRUCTURAL MATERIALS · MECHANICS · GEOTECHNICAL · HYDRAULICS · HIGHWAYS · SURVEYING
Your virtual civil engineering laboratory.
RESIDUAL SETTLED TURBIDITY—
CIVIL INFRASTRUCTURE TELEMETRY
Ready to sample with Alum Dose D = 25.0 mg/L.
Adjust Alum Dose D, then execute civil engineering measurement.
Civil engineering telemetry is evaluated rigorously using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity structural mechanics and geotechnical continuum modeling.
Civil engineering assumptions and boundary condition limits
The civil engineering physical models apply within the specified calibrated operational window (10.0 to 40.0 mg/L). Tested on synthetic turbid river water (initial turbidity = 48.0 NTU, pH = 7.2, alkalinity = 85 mg/L as CaCO3). Linearized regression over the sub-optimal to optimal dose range correlates residual turbidity to alum dose with slope -0.8500 NTU/(mg/L).
Laboratory apparatus & testing equipment.
Laboratory Ratio Nephelometric Turbidimeter
EPA 180.1 compliant tungsten filament nephelometer measuring turbidity to ±0.01 NTU.
Benchtop Digital pH / Ion Selective Meter
Measures water pH to ±0.01 and temperature to ±0.1 °C with automatic temperature compensation.
Six 1000 mL Baffled Glass Griffin Beakers
Contain water samples with internal acrylic baffles preventing vortex core formation during rapid mix.
Digital Micro-Pipettes and Precision Glassware
Accurately doses calibrated stock alum solution (10.0 mg/mL Al₂(SO₄)₃·14H₂O).
Digital Titration Apparatus for Alkalinity
Standard 0.02 N H2SO4 titrator measuring water buffering capacity to methyl orange endpoint.
FOLLOW THE METHOD
A reason behind every step.
Determine the optimum coagulant dosage (alum / polyaluminum chloride) and rapid/slow mixing conditions for maximum turbidity and suspended colloidal particle removal from raw surface water according to ASTM D2035. Standardized parameter settings: 10.0, 15.0, 20.0, 25.0, 30.0, 35.0 mg/L.
01
Raw Water Preparation & Characterization
Prepare 10 L of synthetic turbid water using bentonite clay; measure initial turbidity (48.0 NTU), pH (7.2), and alkalinity (85 mg/L as CaCO3); pour 1000 mL into each of six jar beakers.
02
Jar Tester Setup & Coagulant Dosing
Position beakers under jar test paddles; prepare calibrated alum doses (10, 15, 20, 25, 30, and 35 mg/L) in dosing syringes.
03
Rapid Mixing Phase (Coagulation)
Start paddles at 100 rpm (velocity gradient G ≈ 300 s⁻¹); simultaneously inject alum doses into all six jars; mix for exactly 60 seconds to disperse coagulant.
04
Slow Mixing Phase (Flocculation)
Reduce paddle speed to 30 rpm (velocity gradient G ≈ 30 s⁻¹); mix gently for exactly 20 minutes to promote inter-particle collisions and floc agglomeration.
05
Quiescent Settling Phase
Stop paddles and lift drive assembly cleanly; allow water to settle undisturbed for exactly 30 minutes; observe floc settling velocity and supernatant clarity.
06
Supernatant Sampling & Turbidity Measurement
Extract 25 mL samples from sampling ports located 2.0 cm below liquid surface; measure residual turbidity in calibrated nephelometer; plot turbidity versus dose.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into civil engineering insight.
Points are your recorded observations. The solid regression line validates Jar Test Coagulation mathematical scaling.
LINEAR REGRESSION FIT · y = mx + b
Turbidity = -0.8500 · Dose + 48.00
| # | Alum Coagulant Dosage D (mg/L) | Residual Settled Turbidity (NTU) | Alum coagulant dosage D (mg/L) | Residual settled turbidity (NTU) | Remove |
|---|
No readings yet. Execute a civil engineering trial and record it.
Calculate it yourself.
CHECK YOUR UNDERSTANDING
Explain what the civil engineering metrics mean.
Most colloidal particles responsible for raw surface water turbidity carry a surface electrical charge that is:
The optimal velocity gradient G and mixing duration for the rapid mix coagulation stage are typically:
Sweep flocculation occurs primarily when:
Overdosing alum beyond the optimum point causes settled water turbidity to:
THEORY AND STRUCTURAL CONTEXT
Civil engineering background & physical principles.
In civil environmental water treatment engineering, raw surface waters from rivers and reservoirs contain suspended silt, clay, pathogenic microorganisms, and natural organic matter (NOM) present as negatively charged microscopic colloids (0.001 to 1.0 µm). Due to electrostatic repulsion governed by negative zeta potentials (-15 to -30 mV), colloidal particles remain indefinitely suspended in stable Brownian motion and cannot settle by gravity alone. Coagulation and flocculation destabilize this colloidal suspension. Developed in the 1920s, the standard Jar Test (ASTM D2035) uses a multi-paddle stirrer to optimize chemical dosing in municipal water treatment plants. Adding hydrolyzing metal coagulants—such as aluminum sulfate (alum, Al₂(SO₄)₃·14H₂O) or ferric chloride (FeCl₃)—destabilizes colloids through two primary mechanisms: (1) Charge neutralization: trivalent cations (Al³⁺, Al(OH)²⁺, Al₇(OH)₁₇⁴⁺) compress the electrical diffuse double layer and neutralize negative surface charges; and (2) Sweep flocculation: at higher dosages and neutral pH (6.5 to 7.5), amorphous aluminum hydroxide Al(OH)₃ precipitates en masse, physically entrapping and sweeping suspended particles into settleable flocs. In this laboratory experiment, six 1-liter water samples are dosed with alum from 10 to 40 mg/L, subjected to 1-minute rapid mixing (100 rpm), 20-minute slow flocculation (30 rpm), and 30-minute quiescent settling to calibrate residual turbidity reduction and establish the optimum economic dosage.
Turbidity = -0.8500 · Dose + 48.00
Tested on synthetic turbid river water (initial turbidity = 48.0 NTU, pH = 7.2, alkalinity = 85 mg/L as CaCO3). Linearized regression over the sub-optimal to optimal dose range correlates residual turbidity to alum dose with slope -0.8500 NTU/(mg/L).