Clarifier

Design information for the AguaClara clarifier is available in the Clarifier Design chapter of The Physics of Water Treatment Design

Purpose and Description

The clarifier removes the majority of the particles and pathogens from the raw water source using two distinct mechanisms.

1. Floc filter - Flocs that form a fluidized bed in the lower part of the clarifier are able to capture small particles as water flows through the porous flocs.

2. Plate settlers - Particles with a terminal velocity greater than the plate settler capture velocity (120 μm/s) settle unto the plates and then slide back down into the floc filter as an avalanche

Table 12 Clarifier Figure Key.

Key	Name	Purpose
1	outlet collector	transports the clarified water out of the clarifier chamber
2	plate settlers	capture particles that have a terminal velocity greater than the capture velocity
3	outlet collector channel drain	used during plant maintenance to clean this channel
4	outlet channel drain	dumps clarified water that doesn’t meet specifications
5	inlet dump channel drain	sends poorly flocculated water to the plant waste channel when the inlet collectors are blocked with pipe stubs
6	sludge bleed	dumps flocs from the floc hopper cones
7	clarifier chamber drain	drains the clarifier for maintenance
8	sludge hopper access port	enables inserting a manual mixer into the floc hopper cone to fluidize the sludge
9	inlet collector	delivers flocculated water to the diffusers
10	inlet channel	delivers flocculated water to the inlet collectors
11	inlet dump weir	overflows when the inlet collectors are shut off to prevent poorly flocculated water from entering the clarifier
12	inlet dump channel	dumps poorly flocculated water
13	divider wall	separates flocculated water from clarified water
14	outlet channel	delivers clarified water to pipes carrying clarified water to the filters
15	outlet weir	sets the height of water in the clarifiers and helps ensure equal flow distribution to all of the clarifier chambers
16	outlet collector channel	merges the clarified water from all of the outlet collectors and ensures that all of the clarifier chambers have the same water level
17	plate settler support frame	supports the plate settler modules
18	inlet collector diffusers	create a line jet that extends the full length of the clarifier chamber
19	jet reverser half pipe	reverses the direction of the jets created by the diffusers so that the flow is vertically upward so it can resuspend flocs that have settled on the main chamber hopper
20	floc filter weir	sets the depth of the floc filter in the main chamber
21	floc hopper cone	concentrates the sludge before discharge
22	main chamber hopper	ensures that all flocs that settle to the bottom of the clarifier are resuspended by the diffuser jets
23	main chamber water surface	maximum water level in the main chamber is set by the outlet weir and the head loss through the outlet collector orifices
24	floc filter top surface	marks the transition between the floc filter and the plate settlers
25	inlet collector air vent	discharges air when the main chamber is being filled with water

Fig. 14 Clarifier top view showing the channel system and two clarifier chambers.

Fig. 15 Clarifier isometric view showing the channel system and two clarifier chambers.

Fig. 16 Clarifier side section view showing the water flow path (blue arrows) and the floc flow path (brown arrows).

Fig. 17 Clarifier front section view showing the floc flow path (brown arrows).

Fig. 18 Clarifier top section view showing plate settler support frame, floc weir, and floc hopper cones.

Fig. 19 Clarifier back section view showing the main chamber hopper, diffusers, and jet reverser half pipe.

Fig. 20 Downstream end of inlet collector showing diffusers.

Fig. 21 Diffuser showing isometric, side, and bottom views.

Design Data

Table 13 Clarifier Design Inputs.

Parameter	value
Inputs
Maximum velocity gradient	300 Hz
Maximum upflow velocity	1 mm/s
Capture velocity	120 μm/s
Maximum temperature	30 °C
Minimum temperature	5 °C

Table 14 Clarifier Civil Construction Parameters.

Parameter	value
Number of spare clarifier chambers	0
Overall clarifier width	2.65 m
Overall clarifier length	6.65 m
Height of clarifier measured from the bottom of the jet reverser	1.76 m
Number of clarifier chambers	2
Inside width of each chamber	1.07 m
Inside length of each chamber	5.61 m
Main chamber hopper angle	50 degrees
Channels
Channel wall height	600 mm
Inlet channel width	300 mm
Inlet channel maximum velocity	454 mm/s
Channel elevation increase per outlet	44.1 mm
Inlet dump channel width	150 mm
Inlet dump weir height	525 mm
Inlet dump channel drain nominal diameter	3 inch
Outlet collector channel width	150 mm
Outlet collector channel drain nominal diameter	1.5 inch
Outlet collector weir height	431 mm
Outlet channel width	300 mm
Outlet channel drain nominal diameter	3 inch
Floc Hopper
Floc hopper weir height	840 mm
Floc hopper cone angle	50 degrees
Floc hopper cone height	420 mm
Floc hopper cone top diameter	535 mm
Floc hopper access port nominal diameter	3 inch

Table 15 Clarifier Hydraulic Parameters.

Parameter	value
Maximum chamber flow rate	6 L/s
Inlet Collector
Head loss from inlet to diffuser exit	2.5 mm
Nominal diameter	8 inch
Total length	5.58 m
Air vent diameter	9.53 mm
Port diameter for diffusers	32.1 mm
Diffusers
Nominal diameter	1 inch
Reduced outer diameter for insertion into manifold	32.1 mm
Total length	154 mm
Diffusers per inlet manifold	92
Port diameter in manifold for diffusers	32.1 mm
Center to center distance for diffusers	60 mm
Distance to center of last diffuser from downstream end of manifold	70 mm
Slot width	7.94 mm
Slot length	45.2 mm
Expansion angle	5 degrees
Jet maximum velocity gradient	218 Hz
Jet maximum velocity	179 mm/s
Jet head loss	1.63 mm
Jet reverser half pipe
Nominal diameter	3 inch
Outlet Collector
Head loss from orifice inlets to outlet	50 mm
Nominal diameter	6 inch
Air vent diameter	10 mm
Orifice diameter	15.9 mm
Orifice center to center spacing	100 mm
Sludge drains
Sludge drain nominal diameter	1 inch
Sludge bleed valve nominal diameter	0.5 inch
Plate Settlers
Length	460 mm
Width	1.09 m
Angle from the horizontal	60 degrees
Space between plates	25 mm
Overlap - extra width compared with tank width	16 mm
Number of plate settler modules	16
Number of plates per settler module	11
Number of plates in the last settler module	5