API PUBL 4606-1994

$39.00

Source control and treatment of contaminants found in petroleum product terminal tank bottoms

Published By	Publication Date	Number of Pages
API	1994	113

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Category: API

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Description

SCOPE OF RESEARCH

In the previous API projects (Voung et. al., 1993 & Klock et. al.,
1994), toxicity reduction of tank bottoms after being subjected to
treatment in a sequencing batch biological reactor was investigated.
It was shown that arsenic, copper, zinc, and ammonia present in the
biologically treated tank bottom effluents may contribute to fish
toxicity. A combination of additional treatment: steam stripping to
remove ammonia, iron coprecipitation to remove heavy metals, carbon
adsorption, and UV-peroxide oxidation, subsequent to the biological
treatment were shown to be necessary to reduce the fish toxicity to a
non-toxic level for some but not all the tank bottoms. Implementation
of such multiple treatment processes for tank bottoms is not practical
except perhaps at a very large-scale distribution terminal where
sufficient wastewater treatment expertise and personnel are available.
Even though the multiple treatment processes are technically
implementable at some terminals, they might still be cost prohibitive.
Potential generation of air emission and hazardous wastes are the
additional drawbacks of implementing treatment system on site at
product terminals.

This project approached the problems via a different strategy. Instead
of focusing all the effort on finding technical solutions for the tank
bottom treatment, this project tried to answer two questions: (1)
Through what pathways do the metals, particularly arsenic, and ammonia
enter the tank bottoms; and (2) What source reduction measures can be
taken and to what extent must they occur in the refinery so that the
tank bottoms at petroleum product terminals can be treated to a
non-toxic level on-site.

This project therefore consisted of two phases. In Phase I, the
pathways of the three metals (As, Cu, Zn), particularly As, were
investigated from crude through the refining processes to the tank
bottoms. Speciation of arsenic compounds found in tank bottoms has
been conducted to aid the confirmation of the sources of arsenic.
Selenium and ammonia in the tank bottoms were analyzed, although no
major effort has been devoted to their fates in the refining
processes. In the Literature Review section, it has been shown that
several techniques which remove metals from the hydrocarbon phase can
be potentially used in a refinery to remove metals from refining
process streams, hence reducing the migration of metals from products
to tank bottoms. Based on the findings of this study, different
approaches to reduce the metals from the sources were identified and
recommended.

In Phase II, the upper concentration limits of organics, ammonia, and
metals (As, Cu, and Zn) in the tank bottom that could be treated by
two integrated treatment processes to the non-toxic level were
determined. The two treatment processes were activated sludge coupled
with iron coprecipitation and activated sludge coupled with powdered
activated carbon. The two treatment systems were selected because they
are simple to operate and practical to implement at the distribution
terminal. The results of Phase II study determine the necessity and
the extent that source reduction may be taken to resolve the fish
toxicity issues in the tank bottoms.