Effectiveness of a Large-Scale Ballast Treatment Process

Abstract

A study dealing with the effectiveness of large-scale treatment of ballast water was conducted at the terminal treatment facility of the Alaska Pipeline in Port Valdez, Alaska. Three principal questions addressed by the study were: the effectiveness of petroleum removal from ballast water; the nature of the chemical changes in the process stream; and the suitability of various analytical techniques for monitoring plant operation and measuring the quality of the final effluent. The following analytical operations were performed on-site in Port Valdez: determination of “total oil” by Freon 113 extraction, followed by IR and gravimetric measurement methods; determination of nonvolatile dissolved and nonvolatile suspended organic materials by TOC analysis; determination of volatile organics by gas chromatography; and accumulator column separation and chloroform extraction of dissolved nonvolatile organic matter for subsequent HPLC and GC/MS analysis. It was found that the final effluent contained volatile organic matter composed primarily of aromatic hydrocarbons (benzene, toluene, and xylenes) (48 percent), dissolved organic materials of petroleum nonhydrocarbon type (36 percent), and suspended organic matter which is traditionally defined as water-insoluble “oil” (16 percent). The bulk of the separation of oil from water, it was found, takes place in primary gravity separators (more than 99 percent), and that the secondary aeration-flocculation operation removes only approximately one-half of the remaining fraction of one percent. The studies also showed that standard methods for determination of “total oil” by extraction and either IR or gravimetric methods are insufficient for monitoring the quality of the final treated effluent. This is because the principal organic components in treated effluent are volatile aromatic hydrocarbons and dissolved petroleum non-hydrocarbons. The standard method for “total oil” analysis by extraction-IR is not calibrated for detection of such components, while evaporation of solvent during the gravimetric procedure results in the loss of the largest single group of organics present in the effluent: aromatic hydrocarbons.

Dissolved Hydrocarbons and Related Microflora in a Fjordal Seaport: Sources, Sinks, Concentrations, and Kinetics

“…According to dye studies (Colonell, personal communication), this warm (7 to 1700) effluent floats upward to become trapped below the less-dense surface water which is enriched 10 to 20% by freshwater from stream runoff. Although added hydrocarbons from the effluent would tend to decrease observed oxidation rates if An > KA, the rate maximum of Table 1 showed strong correlation with the plume location from dye studies and from direct hydrocarbon concentration measurements (20). Rate, (ng toluene liter'hr '1) FIG.…”

“…Toluene utilization rates were only approximately 0.01 ,tg/liter per h in the high-activity layer which is small when compared to the 0.4 to 0.9 mg of microbial biomass per liter present. Treated ballast water contains just four major components which are potential growth-supporting heterotrophic substrates: benzene, toluene, xylene, and ethylbenzene (20). Even if 10 other petroleum hydrocarbons were included and endogenous metabolism was neglected, the resulting growth rate from this input would be on the order of 2 per year.…”

“…The residence times of toluene (Table 2) as 1/k1 are given by toluene consumption rates (v) and the concentration of toluene (equation 2) so long as enzymatic processes are not saturated. Comparison of populations in the bacteria-rich layer (Table 1) with those in the holding lagoon (Table 3) where the toluene concentration is known (1.9 mg/liter [20]) gives an estimate of the concen-tration to which toluene in the 50-m sample is diluted based on the assumptions that both bacteria and toluene are equally diluted by fresh seawater and that little growth occurs within the layer itself (Table 2). This computed concentration of An (610 Lg/liter) is sufficient to saturate metabolism (EKi/n = 2.8 ,g/liter; see below) so that the toluene utilization rate is, from equation 8, v = 1.3 ,ug/liter per h. The residence time of toluene in the bacteria-rich layer, using this toluene concentration estimate and disregarding dispersal, is 19 days.…”

“…The rates of dissolved petroleum metabolism that occur in Port Valdez, Alaska, are considered because treated ballast water from oil tankers is pumped into the estuary in large amounts (2 x 106 liters per h) (20). It contains 11 mg of organic material per liter, about half of which is comprised of aromatic hydrocarbons.…”

A Scheme for Analysis of Oily Waters

“…The analytical scheme described here was used with some modifications in a field study of the effectiveness of small-scale bilge water treatment (5) and in a study of the effectiveness of large-scale ballast treatment (6).…”