High Rate Pond (HRP) Operations in California, 1981-1986

III. B.3.a. HRP Design and Construction Phase, 1981

The project described in this section succeeded the projects reviewed in Section III. A. that took place at the University of California-Berkeley. That research group moved essentially intact (as Ecoenergetics, Inc., later renamed EnBio, Inc.) to Fairfield, California, some 30 miles north of Berkeley, with a pond system set up in nearby Vacaville.

The ASP funded this project starting in fall 1980. The objective was to demonstrate the HRP system using agricultural irrigation waters and fertilizers. The HRP was defined as a paddle wheel-mixed (approximately 10-20 cm/s), moderate depth (approximately 15-30 cm), algal production system. The R&D goal was to develop production technology for microalgae biomass with a high content of lipids. A detailed literature review concluded that the best option would be to use N limited (but not starved) batch cultures of green microalgae.

The plan view of the facility is shown in Figure III. B.5. The system consisted of four 200-m2 and three 100-m2 ponds, along with three deep harvesting ponds and four water and effluent storage ponds. This system thus provided considerable flexibility for the testing of a large number of variables and algal species, at a scale that would allow some confidence in the scale-up of the results. The units were lined with 20 mil PVC, to allow complete mass balances.

The report to the ASP describing this work (Benemann et al. 1981) provided considerable detail on the design of the system and the various considerations that went into selection of different design options and operating variables. For example, Table III. B.1. lists the calculations on which basis the carbonation requirements for the ponds were estimated.

After the facility was only partially constructed, the project was terminated by the ASP, as the Hawaii ARPS system, reviewed earlier, was deemed to have already demonstrated its superiority to the HRP design, even before any operations of either. However, after a hiatus of about 1 year, and with changes in the ASP management, funding for the California HRP project was reinstated in August 1982, and actual pond operations were initiated.

image084

Figure III. B.5. Pond system design in California.

The schematic shows the four 200-m2 and three 100-m2 raceway ponds, three deep square algae harvesting (settling) ponds, and the mounds for location of the water supply and media recycle tanks. (Source: Benemann et al. 1981.)

Table III. B.1. Microalgae pond carbonation requirements. (Source: Benemann et al. 1981.)

Quantity

Formula

Example*

X, aver, hourly prod, g/n^.hr

~

1.5

Xp, peak hours prod, g/m2.hr

5

d, pond depth, an

20

A, pond area, л2

200

Q, wt. fraction of C in algae

0.5

F, flow of C02 (ft3)/hr

50

E, carbonator efficiency

0.5

T, terop., °С

25

Peak hourly demand, mmoles C/L. hr

8.3 QXP/d

1.0

Aver, hoursly demand, m moles C/L. hr

8.3 OX/d

0.3

C02 influx, m moles C/L. hr

126.4 EF [298/(273+T)]/ad 0.8

V, linear mixing speed, cm/sec

10

L, pond length, m

30

R, recirculation time, hr

T = .0S6L/V

.16

ДС, C02 influx/carbona^ion pas

(СОг influx) R

.07

pH av

8.0

A, alkalinity, meq/L

10

дрН

(f (pH ava A)

0.3

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