Land Contamination: Technical Guidance on Special Sites: Acid Tar ...

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Box 2.5 Scenario: Acid tar disposal lagoons (continued)By this time, disposal to formal landfill sites was not practicable, due to thereluctance of waste disposal operators to accept acid tars and a correspondingincrease in price per tonne by five times over the three years. The finalmethod chosen involved in situ treatment using quicklime to neutralise theacid tars together with Fuller’s Earth. After the tar and quicklime had reactedand settled down (releasing a considerable amount of heat and steam), thetreated material was re-deposited in layers, compacted, covered with subsoiland landscaped.This second, in situ, remedial exercise took six months, twice as long as thatof three years previously where the wastes were taken away. The area whereacid tar wastes remained became a recreation ground whereas the otherremediated areas where the tars were removed and replaced with limestonewere redeveloped for light industrial units. The remediation by quicklimeappears to have been successful, although generally the method of dispersionby chemical reaction was considered preferable. Similar treatment methodsat another site were less successful, and should therefore be subject totreatability trials.The principal receptors of concern were:• human health – associated mainly with the highly corrosive acidicconditions and also the physical hazard of fires and unstable ground;• groundwater and surface waters – particularly from mobile oils anddissolved phase contaminants;• adjacent buildings and infrastructure – due mainly to the instability ofthe lagoon, mobility of the tars that had broken through to the surface andfire.R&D <strong>Technical</strong> Report P5-042/TR/04 14
3. CHEMICAL AND PHYSICAL CHARACTERISTICSOF THE PRINCIPAL CONTAMINANTSKEY QUESTIONS ANSWERED IN THIS SECTION1. What are the chemical and physical characteristics of acid tars?2. What classes of chemicals are found?3. What typical concentrations of these chemicals could be expected?4. What specific contaminants are found?5. How do the main contaminants behave in the environment?3.1 ScopeThis section presents an overview of the characteristics of acid tars. It includes informationrelating to their chemical and physical form, toxicity and behaviour in the environment.Key information on the physical properties of acid tars is given in section 3.2 whilst section3.3 provides chemical characterisation. Comments are also made on breakdown products ofacid tars and mobility of chemicals present within the environment. A list of the chemicalsthat are potentially present in acid tar lagoons is in Appendix B.3.2 Physical Properties3.2.1 ViscosityAcid tar is thixotropic i.e. it is relatively solid, becoming more liquid when agitated. It has arelatively low density of approximately 1.3 tonnes/m 3 (lower than soil) and the viscosityvaries markedly with temperature, becoming less viscous and more free-flowing during thesummer months as the tars warm. In such conditions, tars may ‘bleed’ and rise throughcovering materials above to spread laterally across the surface. Depth considerations areimportant; with the surface layers typically being weathered to leave a thick and crustysurface, whilst more liquid conditions exist at depth.As discussed in Section 2, the viscosity of acid tars varies with the refining process that gaverise to them (white oil refining generally giving rise to thicker tars than benzole refining).Viscosity also varies with the specific process conditions such as contact time of acid with theoils being refined and so conditions may be highly heterogeneous within the same lagoon ordisposal site.R&D <strong>Technical</strong> Report P5-042/TR/04 15
Page 1 and 2: Land Conta
Page 3 and 4: CONTENTSFOREWORDiGLOSSARYii1. Intro
Page 5 and 6: FOREWORDPart IIA of the Environment
Page 7 and 8: CresolsCreosoteDCRDesorptionDesulph
Page 9 and 10: PVCRCRASelosafeSodium saltsSodium h
Page 11 and 12: 1. INTRODUCTION1.1 BackgroundThis r
Page 13 and 14: SECTION 2: INDUSTRIAL PROCESS/FACIL
Page 15 and 16: 1.5 Linkages Between the Gu
Page 17 and 18: 2.1.2 Overview of acid tar lagoon s
Page 19 and 20: Overall CommentsAcid tars can be of
Page 21 and 22: White Oil• Acid tar lagoons from
Page 23: Box 2.5 Scenario: Acid tar disposal
Page 27 and 28: Table 3.1 - General Physical Charac
Page 29 and 30: The chemicals listed in Table B.1,
Page 31 and 32: 4.2.3 Common mistakesIt is possible
Page 33 and 34: Geophysical methods, such as resist
Page 35 and 36: Investigation locations will need t
Page 37 and 38: • gas chromatography by simulatin
Page 39 and 40: 5.2.2 Water environmentThere is lit
Page 41 and 42: 5.3 Assessment of Investigation Dat
Page 43 and 44: 6. REMEDIATION ASPECTSKEY QUESTIONS
Page 45 and 46: 6.2.5 Solidification and stabilisat
Page 47 and 48: Box 6.1 Example of Remediation of A
Page 49 and 50: 6.3 Natural AttenuationNatural atte
Page 51 and 52: Table 6.1 - Remedial Options/Techni
Page 53 and 54: Table 6.2 - Remedial Options/Techni
Page 55 and 56: 6.4 ValidationThe principles of val
Page 57 and 58: • all personnel should follow a d
Page 59 and 60: Verschueren (1983) Handbook of Envi
Page 61 and 62: USEPA. Innovative Site Remediation

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