Process Water Database

Whereas a substantial database exists for the clean water performance of many diffused aeration systems, the process water oxygen transfer data is limited. The in-process database presented here is from field-scale measurements using currently acceptable measurements (see Chapter 7). The majority of this information is for porous diffusers, primarily because most of the new and retrofit systems installed on municipal systems where information is a matter of public record have employed these high efficiency devices.

Summaries of process water performance data are presented for nonporous and porous diffuser systems in Tables 3.13 through 3.17. Many of the process variables described under clean water tests are provided in these tables. It should be noted that the values of alpha are the mean weighted values and the ranges that are reported

TABLE 3.12

Sources of Information for Equation (2.53)

Parameter Source of Information

theta Normally 1.024, clean water test omega Pressure correction for tau Temperature correction for

C_∞20^*

C_∞20^* C_∞20^*

TABLE 3.13

Process Water Performance — Municipal Nonporous Diffusers

Diffuser Type and Placement Flow Regime

Density (No./m²)

Submergence H_s, (m)

G_sd (m³_N/h -diff)

αSOTE/Hs

(%/m)

ααα α

Nitrification Reference Mean

Weighted Min–Max

Fixed orifice tube Dual^a Step 0.50 4.6 18.0 2.2 1.07 0.83–1.19 No Redmon et al., 1983

Coarse bubble Grid — 0.35 4.1 15.7 1.9 0.94 — Yes Groves et al., 1992

Coarse bubble Grid — 0.35 4.1 15.5 1.6 0.80 — Yes Groves et al., 1992

Coarse bubble Spiral — 0.39 4.0 26.8 1.2 0.60 — Yes Groves et al., 1992

Coarse bubble Spiral — 1.25 3.8 18.7 2.3 0.88 — Yes Groves et al., 1992

Coarse bubble Mid-width — 0.31 4.3 15.4 1.2 0.57 — Yes Groves et al., 1992

Coarse bubble Grid — 0.53 5.8 23.6 1.6 0.55 — Yes Groves et al., 1992

Coarse bubble Grid — 0.36 5.2 22.5 1.9 0.64 — Yes Groves et al., 1992

Fixed orifice tube Spiral CSTR — 4.0 15.5 m_N³/h-m² 1.9 0.75 0.67–0.83 — EPA, 1985

Jet aerator Directional Plug 0.08 4.4 22–74 2.0 0.69 0.52–0.91 No Yunt, 1990

Jet aerator Directional CSTR 0.19 3.8 11.0 2.9 0.45 0.40–0.50 No Brochtrup, 1983

Jet aerator Directional CSTR 0.19 3.8 34.5 2.0 0.47 0.46–0.48 No Brochtrup, 1983

a Third pass of aeration tank (m_N³/h) × 0.64 = 1.57 scfm m = 3.28 ft

From EPA (1985) Summary Report — Fine Pore Aeration Systems, USEPA, EPA/625/8-85/010, Oct. 1985, Water Engineering Research Laboratory, Cincinnati, OH.

© 2002 by CRC Press LLC

TABLE 3.14

Process Water Performance — Municipal Porous Tube Diffusers

Diffuser Type and Placement Flow Regime

Density (No./m²)

Submergence H_s (m)

G_s^a

(m³_N/h -m²) Nitrifying

αSOTE/Hs

(%/m)

Alpha

Reference Mean

Weighted Low–High

PVC membrane Grid Plug 2.3 5.8 12.3 No 2.3 0.43 0.35–0.54 EPA, 1989

PVC membrane Grid Plug 1.2 — 11.5 ? 1.6 — — EPA, 1989

Porous plastic Grid Plug 3.3 4.0 7.3 ? 1.8 0.28 0.26–0.29 EPA, 1989

Porous plastic Spiral Plug 5.2 3.7 3.2 Some 1.8 0.56 0.42–0.67 EPA, 1989

Porous plastic — — — 6.1 — Yes 2.7 — 0.45–0.50 Stenstrom, 1997

EPDM membrane — — 1.2 3.4 8.9 Low 2.0 0.4 — Stenstrom, 1997

EPDM membrane — — 1.4 6.6 2.5 Yes 3.7 0.73 — Stenstrom, 1997

Ceramic Spiral Plug 0.5 4.0 4.1 No 1.5 — — Leary, 1969

Ceramic Cross Plug 0.6 4.0 4.4 No 1.5 — — Leary, 1969

EPDM membrane Grid — 1.2 5.3 4.5–5.9 Yes 1.7–2.4 — 0.32–0.55 Groves et al., 1992

EPDM membrane Grid — 0.8 4.1 1.5 Yes 2.7 0.46 — Groves et al., 1992

EPDM membrane Grid — 0.8 4.1 3.9 Yes 2.1 0.73 — Groves et al., 1992

EPDM membrane Grid — 1.9 4.0 9.6 No 1.6 0.28 — Groves et al., 1992

EPDM membrane Spiral — 1.9 4.0 8.9–11.6 No 1.2 0.34 — Groves et al., 1992

EPDM membrane Grid — 2.3 3.9 4.9–7.1 Yes 2.1–2.7 — 0.33–0.48 Groves et al., 1992

EPDM membrane Grid — 2.4 5.8 4.7–6.4 Yes 2.4–2.5 — 0.43–0.45 Groves et al., 1992

a Gas flow per unit tank surface area (m_N³/h/m²) = 0.059 scfm/ft² m = 3.28 ft

© 2002 by CRC Press LLC

TABLE 3.15

Process Water Performance — Municipal Ceramic/Plastic Domes and Discs — Grids

Diffuser Type

Dome Plug 26 4.6 4.7 No 2.4 0.43 0.31–0.57 EPA, 1989

Dome Plug 26 4.6 3.9 Yes 3.7 0.66 0.56–0.79 EPA, 1989

Dome Plug 7 4.3 6.6 No 2.2 0.41 0.23–0.58 EPA, 1989

Dome Plug 9 3.8 5.4 No 1.8 0.24 0.11–0.39 EPA, 1989

Dome Step 8 4.6 9.0 No 1.5 0.27 0.24–0.31 EPA, 1989

Dome Plug 10 4.2 6.3 No 1.9 0.29 — EPA, 1989

Dome Step 5 4.1 7.3 No 2.3 0.43 — EPA, 1989

Dome Step 5 4.1 7.3 Yes 2.5 0.43 — EPA, 1989

Dome Step 14 4.1 6.6 Yes 3.3 0.52 0.45–0.59 EPA, 1989

Dome Plug 6 3.0 3.6 No 2.2 — — EPA, 1989

Dome Plug/Anoxic 7 3.0 3.6 Yes 3.3 — — EPA, 1989

Dome ? 7 3.75 5.2 No 1.9 — 0.10–0.35 Stenstrom, 1997

Dome ? 7 4.0 5.8 No 1.8 0.30 — Stenstrom, 1997

TABLE 3.15 (continued)

Process Water Performance — Municipal Ceramic/Plastic Domes and Discs — Grids

Diffuser Type

Flow Regime

Diffuser Density (%)

Submergence H_s (m)

G_s^a

(m³_N/h –m²) Nitrifying ααα αSOTE/Hs

(%/m)

Alpha

Reference Mean

Weighted Low–High

Ceramic disc Plug 8 4.9 3.4 Yes 3.0 0.2 0.19–0.22 EPA, 1989

Ceramic disc Plug 9 3.8 4.2 No 2.4 0.31 0.21–0.40 EPA, 1989

Ceramic disc Step 7 4.4 6.1 Yes 2.1 0.35 0.28–0.54 EPA, 1989

Ceramic disc Plug 11 4.2 5.6 No 1.9 0.28 — EPA, 1989

Ceramic disc ? 9 3.7 4.4 Yes 2.4 — 0.3–0.4 Stenstrom, 1997

Porous plastic disc ? 10 4.0 6.9 No 1.8 0.3 — Stenstrom, 1997

Ceramic disc ? 11 5.1 9.7 No 2.1 0.35 — Stenstrom, 1997

Ceramic disc ? 8 4.8 2.7 No 2.4–2.8 — 0.35–0.41 Groves et al., 1992

Ceramic disc ? 11 5.7 7.6 Yes 3.8 0.60 — Groves et al., 1992

Porous plastic disc ? 6 4.0 12.4 No 2.1 0.33 — Groves et al., 1992

Ceramic disc ? 10 4.4 8.3–11.3 No 2.9 0.50 — Groves et al., 1992

Ceramic disc ? 10 4.5 3.1–3.9 Yes 3.3–4.2 — 0.5–0.61 Groves et al., 1992

Ceramic disc ? 10 5.2 3.9 Yes 3.6 0.52 — Groves et al., 1992

a Airflows per unit tank surface area 1 m = 3.28 ft; 1 m_N³/h-m² = 0.059 scfm/ft²

© 2002 by CRC Press LLC

represent temporal variations of these mean weighted values and not spatial varia-tions within the aeration system. Spatial variavaria-tions in alpha (and αSOTE) are addressed later. The values of alpha were determined from clean water test data for similar tank geometries, airflow rates, diffuser densities, and placements. As described above, many of the data were collected after the diffusers were in service for significant periods of time. Therefore, the value of alpha reflects both the impacts of wastewater constituents and changes in diffuser characteristics. Values of αSOTE were calculated from field data by correcting to standard conditions of temperature, pressure, and basin DO of 0 mg/L.

It must be emphasized that this in-process oxygen transfer data represent the results of many oxygen transfer tests, each conducted over a period of several hours duration. The data should not be used for design purposes. It is provided to give some insight into the range of values observed in primarily municipal wastewater and to illustrate the effects of selected process variables on performance.

TABLE 3.16

Oxygen Transfer in Process Water — Municipal Perforated Membrane Discs/Panels — Grids

Disc 6 4.6 40.7–57.6 No 3.0–3.1 0.47–0.50 Egan-Benck et al.,

1992

Disc 7 4.6 45.8–54.2 Yes 2.6–2.8 0.42–0.45 Guard et al., 1990

Disc 33 4.0 7.5–11.1 Yes 6.0–6.4 0.68–0.76 Sanitaire, 1993

Disc 12 5.1 55.9–72.9 Yes 2.3–3.0 0.44–0.48 Currie & Stenstrom, 1994

Disc — 4.0 — Yes 3.0 — Stenstrom, 1997

Disc 10 5.6 45.7 Some 3.5 0.53 Stenstrom, 1997

Disc 28 4.3 9.5 No 4.1 0.51 Stenstrom, 1997

Panel^b 51 4.7 11.3 Yes 5.0 0.66 Dezham et al., 1992

Panel^b 51 4.7 9.7 Yes 4.4 0.57 Dezham et al., 1992

Panel^b 51 4.7 9.0 Yes 3.6 0.49 Dezham et al., 1992

Panel^c 51 4.7 5.6 Yes 4.5 0.52 Dezham et al., 1992

Panel 38 5.1 12.5–16.4 Yes 2.9–3.6 0.42–0.52 Currie & Stenstrom, 1994

Panel 66 4.0 3.3–4.9 Yes 6.8–7.1 0.7–0.72 Sanitaire, 1993

Panel 40 4.6 8.1–8.6 ? 3.5–4.0 — BBS Corp., 1990

Panel 42 4.6 12.9 Yes 3.6 0.59 Stenstrom, 1997

a Gas flow per diffuser surface area

bConsecutively new, 6 months, and 11 months of service

c Following cleaning

1 m = 3.28 ft; 1 m_N³/h-m² = 0.059 scfm/ft²

As discussed above, several design and operational variables affect the perfor-mance of aeration systems. The lack of controlled studies makes it difficult to draw strong conclusions regarding the impact of many of these variables. The following sections discuss the observations made to date from in-process test data.

In document Volume 11 - AERATION Principles and Practice (Page 106-112)