Calling in the effluent experts
Process Engineer at Atkins Water, Fred Gould, discusses the benefits of using an integrated and inclusive approach to dealing with industrial wastewater.
For the majority of industries the overriding concern is production: the product may be expensive and complex or cheap and cheerful, but successful industries need to focus on the core issues relating to efficient development and production that is responsive to customer needs. As managers and production staff focus on the production process itself, it often happens that aspects such as water supply and wastewater treatment do not get the attention they require, particularly where the cost implications for a product are proportionally small. Where this is the case it is not easy for industries or plants to select efficient and appropriate technologies for wastewater treatment themselves as management lack the breadth of knowledge and cannot afford the time to research the problem in more detail. The position is likely to become more complicated as existing EC Directives covering areas such as dangerous substances and water and environmental protection feed through into the European legislative environment. Therefore, a role exists for consultancies with the broad range of expertise required to be able to look at wastewater treatment within the current and future legislative environment. The attractiveness of such consultancy to industry will be much higher where it can be sensitive to the process requirements of a particular industry or plant. From an industry's point of view it is often most efficient for a consultant to work with the industry to develop an integrated approach to both the manufacturing process and wastewater treatment; where a consultancy has the necessary experience of industrial processes; an established reputation; and can be relied upon to do a good job. Handing over responsibility for more than just wastewater treatment need not be so daunting. Process technology
The consultant will initially characterise the effluent from the existing plant and identify suitable process technology to treat it to the required future standard. The next step is to consider, in consultation with the client, the options within the manufacturing process to either improve the treatability of the wastewater or to reduce the quantity to be treated. To ensure that the local management 'buy in' to any proposed changes it is essential to ensure an inclusive and consultative approach is maintained with the client and particularly with the local staff that will require to operate any new processes. Any proposed changes should be of minimum cost and ensure compliance with regulations ideally whilst improving plant operation. A stage by stage approach may be appropriate as it gives clients time to assess what is and is not justified within their budgets set against the regulatory background. In an ideal world the focus would be for the Consultant to free the client from the responsibility of identifying and evaluating possible solutions to wastewater treatment. The consultant can take the load off the client who would otherwise have to go through the very difficult process of interfacing with the authorities, keeping up to date with the actual legislation and choosing technologies and processes.Integrated solutions
As a consultancy with wide-ranging experience, Atkins has a dedicated Industrial Process Division that works closely with the Water Division in identifying and offering integrated solutions to industry, broadening the scope of the expertise that can be offered and bringing together proficiency in industrial processes and effluent treatment processes as well as knowledge of the relevant legislative framework. Atkins has a large number of Blue Chip companies as clients and has vast experience of various industrial effluents, having helped these clients select technologies and processes that uniquely address their specific circumstances. Atkins is able to identify the technologies and processes that are most suitable for their particular effluent, and to quantify the problems on a case by case basis. Analysis of the nature of the effluent, how the effluent is produced, the potential for waste minimisation and the current processes used all aids the decision as to which solutions would be most appropriate. The wastewater treatment solution can range from simple physico-chemical processes to complex treatment to produce a high quality effluent or to separate particular materials for separate disposal or recycling. To be most effective the manufacturing process itself will also be considered and the success of this approach is reliant on the experience and competency of the consultant used.
There are various methods available to industry for treating effluent. Two popular methods for removing suspended solids from effluents are Dissolved Air Flotation (DAF) and Ultra Filtration. For removal of precipitated heavy metals, and also liquids immiscible with water such as solvents and oils, DAF is often used. This involves treatment with coagulants and flocculants and pH adjustment if necessary prior to flotation and removal of the material that is floated to the surface. The process involves mixing high pressure water containing dissolved air through a nozzle system into the effluent to be treated: the air comes out of solution forming bubbles on the pollutants which act as nuclei. The pollutants then float and are removed by a skimming mechanism. This is a very common method but has some drawbacks including the problem of handling chemicals.Value-added sectors
Ultra filtration is a more sophisticated method, popular in the high value-added chemical and pharmaceutical sectors. It involves using semi-permeable membranes which permit the passage of liquid whilst retaining all but the smallest solids, producing an effluent very low in suspended solids. Drawbacks include a high capital cost and the risk that the life of the expensive membranes might be shorter than expected due to poor operation or other factors. When choosing a membrane for this process it is important that the membrane used has a proven record of success with effluents of similar nature to those being considered. Membranes are expensive and to minimise operational cost it's essential to ensure that the wastewater is compatible with the membranes proposed. In the last 10 years or so, membranes have improved markedly in their robustness and their ability to treat a wide variety of industrial wastewaters. In many instances, the 'waste material' produced by ultra filtration is valuable material that has been diluted in the production process (e.g. tank washes). Where material recovery offers no advantages in its own right, ultra filtration may well be economic by ensuring that a plant's trade effluent charges are reduced due to a lower strength effluent.
Ultra filtration is a technique which is not applicable to all wastewater, illustrating an important point - there are many processes available but some are more suitable for a particular industry or plant than others. What is appropriate for a pharmaceutical plant may be inappropriate for, say, the textile industry. In order to be confident that a particular technology is suitable for a particular industrial plant it is necessary to look at the whole spectrum of industrial processes that are or could be used and the whole spectrum of treatment options and then match them together in a manner to fit within any site constraints.Treatment options
Atkins was recently employed to consider treatment options for a wastewater that contained a variety of solvents and heavy metals. We characterised the effluent, and undertook detailed analysis to establish the volume and strength of the effluent and to then identify possible methods for pre-treatment prior to ultra filtration. The solution identified was an off-the-shelf fine screening system which provided sufficient protection to the membranes. A long-term trial confirmed both the suitability of the selected pre-treatment and the ability of ultra filtration to successfully treat the effluent to a high standard. There were no problems with the membranes themselves. The new system delivered enormous benefits to the client - both financial and in achieving their discharge consent and complying with the Integrated Pollution Prevention and Control (IPPC) application. It was also apparent that it would also be practicable to recycle a significant volume of this treated effluent rather than discharge it to sewer.
With the regulatory arena becoming increasingly complex and technological developments and treatment systems increasing the choices for industrial wastewater treatment, it is becoming ever more difficult for industry to identify the best treatment options, particularly in this period of changing environmental legislation. There is therefore an increasing role for specialist consultants to assist companies in choosing appropriate and efficient solutions for wastewater treatment. The value of such advice is enhanced where the consultant can offer an integrated approach, looking at the upstream processes in addition to wastewater treatment. Where this approach is taken it is essential that clients and local management are involved throughout the whole process to ensure 'buy-in' by those who will be responsible for future operation. As a consultancy with a multi-disciplinary team encompassing expertise in both wastewater and industrial process Atkins are able to provide such services.