Performance of Aerated Lagoon Intermittent Sand Filter Hamburg Plant

Parameter

1990

1991

(January to August)

Average flow rate (m3/d) 1676 1673

Maximum flow rate (m3/d) 4530 3990

Raw Sewage BOD (mg/L) TSS (mg/L) TKN (mg/L) TP (mg/L) Aerated Cell HRT (d)

BOD loading (kg/m3-d) Aerated Cell Effluent

BOD (mg/L) TSS (mg/L) TP (mg/L) Facultative Lagoon HRT (d)

Average BOD loading (kg/1000 m2-d) Cell 2 Effluent

BOD (mg/L) TSS (mg/L) TKN (mg/L) NH3-N (mg/L) NO(T)—N (mg/L) TP (mg/L)

Filter

Annual surface loading (m3/m2) Surface loading (L/m2-d) Filter Effluent

BOD (mg/L) TSS (mg/L) TKN (mg/L) NH3-N (mg/L) NO(T)-N (mg/L) TP (mg/L)

Source: Melcer, H. et al., Water Sci. Technol, 31(12), 379-387, 1995. With permission.

314 45 9.3

0.03

34 44 6

165 0.51

3240

March to December

120 171

36 44 5

165 0.55

153 3240 March to August

TABLE 5.8

Lagoon-Intermittent Sand Filtration Run Lengths

Hydraulic Loading Rate Days of Filter Operation

TABLE 5.8

Lagoon-Intermittent Sand Filtration Run Lengths

Hydraulic Loading Rate Days of Filter Operation

Sand Characteristics

(m3/m2/d)

Before Initial

Sand 1 (e.s. = 0.70 mm;

U.C.

= 2.1)

0.2

469

0.9

335

1.1

106

Sand 2 (e.s. = 0.35 mm;

U.C.

= 1.4)

0.2

468

0.7

259

0.9

16

Sand 3 (e.s. = 0.37 mm;

U.C.

= 7.0)

0.2

130

0.4

305

0.6

159

0.7

27

0.9

9

Sand 4 (e.s. = 0.18 mm;

U.C.

= 2.7)

0.2

131

0.4

130

0.7

35

0.9

5

Source: Truax, D.D. and Shindala, A., Water Environ. Res, 66(7), 894-898, 1994. With permission.

Source: Truax, D.D. and Shindala, A., Water Environ. Res, 66(7), 894-898, 1994. With permission.

sand. An alternative is to use gravel around the underdrain piping and then a permeable geotextile membrane to separate the sand from the gravel. Further details on design and performance are presented in USEPA (1983). A design example for an intermittent sand filter treating a lagoon effluent is presented in Example 5.1.

Example 5.1. Typical Design of Intermittent Sand Filter Treating Lagoon Effluent

Design data and assumptions:

2. Hydraulic loading rate = HLR = 0.29 m3/m2-d (0.310 MG/ac-d).

3. Minimum number of filters = 2.

4. Design to minimize operation and maintenance.

5. Gravity flow is possible.

6. Topography and location satisfactory.

7. Adequate land is available at reasonable cost.

8. Filter sand is locally available.

9. Filters are considered plugged when, at the time of dosing, the water from the previous dose has not dropped below the filter service.

TABLE 5.9

Summary of Reported Annual Maintenance For Field-Scale Facilities

TABLE 5.9

Summary of Reported Annual Maintenance For Field-Scale Facilities

Mt. Shasta

Moriarty

Ailey

Job Description

Facility

Facility

Facility

Daily operation and maintenance

(1.0 hr) x 7 d x

(1.0 hr) x 7 d x

(0.5 hr) x 5 d x

(daily monitoring)

52 wk = 364

52 wk = 364

52 wk = 130

Filter cleaning

54a

28a

None

Filter raking

12 raking; 16 mixing

13

22

Filter weed control

NA

None

26

Miscellaneous maintenance

NA

11

None

Grounds maintenance

42

8

28

Total reported man-hr/yr

488+

424

206

Computed manpower requirements

2.4 man-yrb

1 man-yrb

1 man-yrb

Actual reported manpower input

2.0 man-yrc

0.28 man-yrb

0.14 man-yrb

a Man-hours with mechanical assistance. b Assuming 1500 man-hr per 1 man-yr.

c Considering extra assistance for filter cleaning and weekend monitoring. Source: Data from Russell et al. (1980, 1983).

a Man-hours with mechanical assistance. b Assuming 1500 man-hr per 1 man-yr.

c Considering extra assistance for filter cleaning and weekend monitoring. Source: Data from Russell et al. (1980, 1983).

Design

Determine dimensions of filters:

Area of each filter = g/HLR. Area = 1307 m2 (0.323 ac). Length-to-width radio = 2:1. W = 25.56 m (83.87 ft). L = 51.13 m (167.7 ft).

A minimum of two filters is required.

Influent distribution system Design assumptions:

1. Dosing syphon will be used to gravity feed filters. Electric activated valves also may be used.

2. Loading sequence will be designed to deliver one half the daily flow rate to one filter unit per day in two equal doses. More frequent dosing is acceptable.

3. Pipe sizes are selected to avoid clogging and to make cleaning convenient. Hydraulics do not control.

Dosing basin sizing:

Number of dosings per day = 2. Q = (design Q)/(number of dosings) = 189.5 m3/d. Volume = 189.5 m3.

Install overflow pipe to filters. Distribution manifold from dosing siphon should be designed to minimize the velocity of water entering the filter. Use 10-in.-diameter pipe in this design. Each of the outlets from the manifold will be spaced 10 ft from each end and 21 ft on-centers on the long side of the filter. Manifold outlets will discharge onto 3-ft x 3-ft splash pads constructed of gravel 1.5 to 3 in. in diameter.

Filter containment and underdrain system

The filter may be contained in a reinforced concrete structure or a synthetic liner to prevent groundwater contamination. The slope of the filter bottom is dependent on the slope of the drain pipe configuration. Use a slope of 0.025% with lateral collection lines 15 ft on-center. Six-inch lateral collecting pipe and 8-in. collection manifolds will provide adequate hydraulic capacity and ease of maintenance.

Minimum freeboard required for filters: Must be adequate to receive one dosing x safety factor. Safety factor = 3.

Depth = (SF x Qdosing)/(L x W) = (3 x 189.5)/(25.56 x 51.13). Water depth assuming no passage through filter = 0.435 m (1.47 ft).

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