Oscar performance for ODW
Industrial Waste Treatment is a specialist in processing difficult effluents. The firm's Oscar system treats oily waters and recovers both oil and water for re-use in the client's processIndustrial Waste Treatment (IWT) was founded in 1999 for the research, development and implementation of wastewater management systems to treat a range of difficult aqueous wastes. IWT's product and service line consists of the design, build, installation and servicing of wastewater management systems including advanced evaporation systems, membrane systems and specialised filtration systems.
The Oscar (oil separation, concentration and recovery) advanced evaporation system has been developed over a three-year period and combines a range of new and existing technologies to produce a versatile system. Oscar can process a range of aqueous wastes, for example oily dirty water (ODW) where the result has been a 'finished' water suitable for re-use or disposal to drain and the capturing of emulsified oil content for re-processing.
The principal existing methods of ODW treatment are predominantly by heavy chemical dosing, dissolved air flotation, biological treatment or any combination thereof. Physical settlement and dilution are also methods widely used. Potable water is sometimes mixed with the effluent so it is diluted and will meet the current discharge consents, but this method impacts even further on the environment by increasing the volumes discharged.
Compared to its own plant Industrial Waste Treatment believes the above methods are generally either ineffective or expensive and do not always provide water suitable for reuse within a process or capture valuable bi-products. The ODW feedstock consists of free oil floating on the surface, solids, oil/water emulsion (dirty water). Types of oils found in ODW range from insoluble hydraulic, crude and bunker oils through to oils that contain entire packages of additives or detergents and soaps. The effluent typically contains traces of heavy metals which, in the ionic form, act as emulsifying agents known as hydrophilic colloids. Obvious to the naked eye will be general dirt, grit and sludge. It is also possible to detect solvents of various species. The Oscar system comprises five separate stages:
- the preliminary separation of free oil from the emulsified feedstock,
- the removal of solids from the feedstock,
- removal of speciated VOCs from feedstock using a specially designed filtration media,
- low-pressure, forced re-circulation decanting system combined with Accelerated Phase Separation (APS),
- removal of any residue hydrocarbon/ VOC from the feedstock.
The entire plant is controlled by PLC to guarantee a continuous facilitated automatic process. One application for the system was with a leading collector and re-refiner of waste and spent hydrocarbon which generated a substantial volume of ODW emulsion as a process by-product. This waste material contains around 7-15% emulsified oil, VOCs, heavy metals and solvents. In addition to general detritus, the effluent typically has a average COD value of 87,000mg/l although this can be as high as 200,000mg/l. The effluent's characteristics prohibit discharge to foul sewer, necessitating removal from site under the provision of a waste management licence for disposal by a specialist contractor. Aware of the implications of impending legislative changes and the potential effect on disposal cost, Industrial Waste Treatment proposed an alternative methodology to address the problem. The ODW is an emulsion created from a process causing the oil fraction to be mechanically, chemically and electronically bonded to the aqueous phase.
Alternative treatment technologies were considered and tested, including membrane and chemical separation, but without success. Industrial Waste Treatment concluded existing technologies could not provide a reliable, cost-effective way to treat the inconsistent nature of the feedstock on a continuous basis. Low-pressure evaporators have been in existence for more than 50 years, however operational cost has made the technology prohibitively expensive. There have also been problems when the approach has been applied to materials that may contain 'light end' hydrocarbons as these evaporate preferentially to water and therefore contaminate the distillate stream. In an attempt to address both issues Industrial Waste Treatment's system has a heat recovery system and patented system for VOC capture known as APS. Results to date show a reduction in energy input of 60% when compared with the traditional evaporators, together with 86% removal of VOCs present. To support the evaporator plant the company has developed pre and post-treatment using a modified organic clay compound for both feedstock and processed water streams to ensure not only compliance, but enhanced reliability in the plant operation.
The system has reduced COD at the point of discharge to an average of 1-2,000mg/l, enabling the re-use of treated water within the client's process. A further benefit is derived from the return of oil, which is suitable for inclusion within the re-refining process. Excess water is safe to discharge to foul drain. made to measure Industrial Waste Treatment installs bespoke systems and plant specification is therefore dependant upon the percentage of oil in the feedstock and the client's requirements for disposal or re-use of the processed water. However, using Oscar technology for ODW the following results can be achieved.
Plant can be built to treat volumes up to 10 tonnes/h, typically over 24h, 330 days per annum. Typically the Oscar plant can treat effluent containing up to 20% oil. This will produce a concentrated oil residue of around 85%. Smaller volumes of effluent with a high oil content of up to 70% can be treated with an Oscar II unit. Typically these plants operate at around 1 tonne/h. Plant is skid mounted, with the exception of pre and post-filtration. The size of the plant is dependent upon capacity treated, but typically a plant to treat 6 tonnes/h will fit onto a skid of approximately 18x12x4m.
The Kalpac filtration system represents an evolving oil/water separation technology. The product is a versatile filtration medium that can be used in pre-treatment, post-treatment or stand-alone treatment processes. Kalpac is a type of organically modified clay able to remove mechanically emulsified oil and grease from water, thus extending the life of granular activated carbon by seven times or more. Kalpac also has the capacity to remove heavy metals, both in cationic and anionic forms.
Kalpac is manufactured by modifying bentonite with quaternary amines, it typically removes seven times the amount of oil activated carbon can, providing a saving for the user of 50% or more in filtration costs.
A combination of Kalpac and activated carbon can easily achieve non-detectable levels of most organics. Such a combination can be used to remove such paraffins, naphthenes and aromatics (PNA) compounds as anthrazene, flourene, pyrene and others, while the carbon then removes the benzene, toluene, ethylbenzene, and xylenes (BTEXs). Antifreeze and aqueous cleaners are filtered through Kalpac beds to remove oils and allow for reuse. Disposal options for spent medium are dependent upon the classification of the organics absorbed. Spent medium can be landfilled, land farmed, incinerated, bio-remediated or blended as a fuel source for firing in cement kilns. Spent Kalpac has a fuel value of up to 18,000BTU/lb, depending on the fuel value of the absorbed organics.
Industrial Waste Treatment has recently used a bed of Kalpac during a series of trials to process ODW. The Kalpac was used for pre-treatment to reduce the amount of oil and grease and importantly the VOCs. The results shown in Table 1 were achieved by one pass through a Kalpac bed with a retention time of 10 minutes.
There are numerous case histories covering the use of Kalpac in a variety of applications including:
- rinse water containing lead where trails showed that by using Kalpac with carbon and ion exchange resin, the lead was organically bound,
- metal plating operations where Kalpac was used to remove oil followed by natural zeolite to remove zinc and thereby ensuring compliance with local regulations.
In addition to the Oscar units, Industrial Waste Treatment has a range of membrane modules and treatment plants. Trials have been carried out for the laundry industry where the company can recycle up to 80% of incoming water and return it for re-use at around 35°C. The recovered water can then be used for normal washing cycles or for warm rinses.
Units can be made in small, skid-mounted modules for the treatment of 1-6 tonnes/h, or in self-contained, container mounted units for 10 tonnes/h and above. This means that they are suitable for small hotel-based laundries, independent and large commercial laundries. Plants are fully automated, requiring little maintenance or supervision - recycling the wastewater when supplies are available and shutting down when not required. In response to a growing problem Industrial Waste Treatment is currently involved in a project to treat and recover glycol. A test unit will be available during summer 2003.
The company seeks to design, build, own and manage systems typically seeking to secure five-year contracts where the client guarantees a minimum annual throughput volume at an agreed rate, eliminating the need for capital expenditure. For those clients preferring to purchase plant, a full service programme is available as well as operator.