The costs of managing fats, oils and grease in the public sewer system is significant, but local authorities can take advantage of their potential and develop anaerobic digestion infrastructure at wastewater treatment plants, writes Sam Crowley
Chem

 

Author: Sam Crowley BEng, MEngSc, MIEI, Crowley Services Ltd

The fats, oils and grease (FOG) issue has received increasing publicity in recent years. Most recently, a 15 tonne wedge of solidified FOG was removed from a foul sewer at Kingston upon Thames, London in July.

The appropriately named ‘fatberg’ incident received significant coverage in the Irish media and was a familiar story for Irish local authority water services staff, who battle the problem in our sewer systems daily. The cost of managing FOG in the public sewer system is significant, with clean-up costs representing up to 60 per cent of overall annual sewer and pumping station cleaning expenditure (Cork County Council, 2008).

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The problem is not a new one, but the development of new wastewater collection and treatment infrastructure has elevated the issue to one of national concern. Considerable strides have been taken by local authorities in recent years to manage the problem and reduce maintenance expenditure. In many regards, Dublin City Council has led the way in this process through their FOG programme, which commenced in 2008. The programme is rightly lauded as a success with over 90 per cent of identified food service establishments (FSEs) now licensed.

However, we are still in the early stages in the resolution of the problem on a nationwide basis, with rates of compliance in many local authority jurisdictions still very low. The experiences of the Dublin City FOG programme should be reviewed to assess if the approach can be improved, in advance of future campaigns elsewhere.

All stakeholders should be taken into account to include local authorities, FSEs and environmental engineering and services providers. Opportunities and challenges exist for each of these stakeholders and the acknowledgement of this can assist in the development of a sustainable FOG management industry.

MANAGING COSTS OF COMPLIANCE

‘Fatberg’ (pic courtesy of Thames Water)

Experience has shown that a large portion of FSEs will comply voluntarily with this legislation without the need for enforcement, but the costs associated with compliance in the management of FOGs has been a barrier in this process. If such costs can be reduced, local authorities will meet less resistance and improvements in the sewer system will be achieved more readily. These costs can be divided as follows:

1.              Trade effluent licence (TEL) application cost

The cost to an FSE in the preparation of a TEL application can be considerable. These costs may include surveys to produce drawings, procurement of Ordnance Survey maps, obtaining and analysis of effluent samples. The application forms can appear complex to a food business operator (FBO), which may not typically deal with this type of information and hence consultants are often engaged to prepare the application.

These costs and perceived technical complexities have been found to deter many of the FBOs, which would voluntarily submit an application. Local authorities should make the application procedure as simple and affordable as possible. Indeed, some councils, such as Dublin City Council, have accepted this to be the case and now waive the necessity to carry out effluent analysis at application stage. This simplifies the process and reduces the cost of application by €100-200.

2.              Recurring annual trade effluent licence fees

In general, trade effluent licensing campaigns are designed to be cost neutral with, the cost of administration balanced by licence fees and savings obtained through lower sewer maintenance costs. Reduction in these fees can only be obtained if savings can be achieved through the streamlining of the administration of the programme.

Method-based consents should be adopted rather than the traditional model, which utilises qualitative effluent analysis to ensure grease management equipment is performing correctly. This is time consuming and costly. Method-based models focus on the carrying out of predetermined levels of maintenance that are generally considered to produce effluent of an acceptable standard.

For example, the grease trap must be pumped out four times per year, with certificates of disposal required to verify the work has been carried out. This model was adopted by Dublin City Council and is far more economical than traditional methods. However, a visual inspection of the grease management equipment is still required and provisions must still be made in the licence for effluent quality limits and effluent analysis in the event of non-compliance.

3.              Capital cost for the installation or upgrade of grease-management systems

Grease-management systems are required to remove FOG from the wastewater at source. The enforcement of this requirement can be a significant challenge for local authorities. Many FSEs do not possess any systems for the management of FOG; others may have existing systems but do not meet current standards. In many properties, it is not feasible to install systems that fully comply with the relevant standards and guidelines (IS EN 1825 for passive grease traps and PDI G101 for Grease Removal Units), for example due to spatial constraints.

The cost to install or upgrade systems can be considerable and may not be within the financial capability of some enterprises. For those who may have purchased such equipment in recent years, the notion of upgrading can be unpalatable and lead to conflict. Additionally, personal experience has found that the installation of equipment which does meet design standards above cannot guarantee compliance with the limits set in a TEL.

Local authorities must consider the best course of action for such cases at the outset of the licensing process, as it may be too late to change policy mid way through the campaign.

In reality, if even a small improvement in the quality of discharge can be achieved by each FSE, a significant positive effect will be found in the condition of the public sewer system. In many cases, it is possible to achieve such an improvement with equipment which is within an acceptable tolerance of current standards. For instance, the implementation of more rigorous maintenance can deliver higher performance.

However to facilitate this, a level of compromise and flexibility is required, which is not something easily achieved in legislation or in the terms of a licence. Whatever policies are adopted by a city or county council, they must be transparent and uniform to avoid situations which disproportionately affect the commercial competitiveness of a given business.

 4.              Maintenance and servicing cost of grease-management systems

All FOG management equipment requires maintenance, which carries some associated costs. Contractors are typically commissioned to maintain grease management systems for FSEs, which includes the regular removal of waste from the systems. Opportunities exist for the environmental engineering and services sectors to develop novel systems for the more economical management of grease-trapping equipment and grease trap waste.

At present, the majority of grease trap waste in Ireland is rendered or composted. These methods are expensive and do not take advantage of the potential of the feedstock. Analysis carried out on various methodologies for the recovery and re-use of grease trap waste has indicated that anaerobic digestion is the most viable option for the Irish market (Crowley, 2010). Research has found that grease trap waste is a particularly attractive feedstock for anaerobic digestion, with the potential of boosting biogas production by up to 30 per cent (Davidsson et al, 2008).

ANAEROBIC DIGESTION INFRASTRUCTURE

Digester tanks in a water treatment plant

Local authorities are in a strong position to take advantage of this potential through the development of anaerobic digestion infrastructure at existing wastewater treatment plants. The development of standalone anaerobic digestion facilities by private industry is not financially attractive due to planning constraints and costs involved in establishing the required infrastructure.

However, the development of such facilities could be carried out using a public private partnership. This would be particularly attractive in the case of facilities for which long-term operating contracts are in place. Such projects could provide significant revenues to the partnership and contribute to the operating costs of the wastewater treatment plant through tipping fees and power generation.

We currently have a number of research projects under way in conjunction with the NIMBUS centre at Cork Institute of Technology, which we hope will lead to a reduction in FOG management costs for FSEs. Initial feedback from market research for these projects has been extremely positive and we look forward to the development and launch of these systems in the next 12-24 months.

The opportunities for local authorities and the environmental engineering and services sectors in the establishment of a sustainable nationwide FOG management industry are clear. However, these can only arise through the collective commitment of the food industry to the correct management of FOG. The food industry must accept that FOG management is a permanent part of their business and should recognise this opportunity.

The establishment of a critical mass of compliant FBOs will create economies of scale and the critical mass necessary for those looking to invest in facilities and infrastructure for the recovery and treatment of FOG. Secure and stable feedstock volumes make the investment of capital more secure and finance more accessible. Contractors will also feel more confident investing in plant, equipment and personnel for the servicing of the FOG management industry.

Once improvements have been made in the sewer network, it is likely that local authorities may be in a position to reduce licence fees. Sewer maintenance costs contribute to the level of council rates and charges that are applied to FBOs and it is possible that if these costs are reduced, these charges will fall accordingly.

Sam Crowley completed both his undergraduate degree in civil & environmental engineering (BEng) and postgraduate degree (MEngSc) at University College Cork. In 2006, he joined Cork County Council to work on the Midleton FOG pilot project, which was completed in 2008. Since then, he has gained experience in the construction, operation and maintenance of water and wastewater treatment and pumping infrastructure with Response Engineering Ltd and with the family business, Crowley Services Ltd. This has included roles as project engineer on projects such as Skibbereen main drainage, Kinsale main drainage, Buttevant main drainage and the provision of storm-holding facilities and ancillary works at Watergrasshill WWTP. Crowley currently works in the Dyno-Rod department of Crowley Services Ltd. 

References

  1. Cork County Council 2008, Midleton FOG Project Final Report, Water Services National Training Group, Roscrea
  2. Crowley, S 2010, ‘A Study of the Re-Use of Waste Fats, Oils & Grease’, MEngSc Thesis, University College Cork
  3. Davidsson, A. Lovstedt, C. la Cour Jansen, J. Gruvberger, C. Aspegren, H. 2008, ‘Co-digestion of grease trap sludge and sewage sludge’, Waste Management. Vol. 28.
http://www.engineersjournal.ie/wp-content/uploads/2013/09/Grease-1024x683.jpghttp://www.engineersjournal.ie/wp-content/uploads/2013/09/Grease-300x300.jpgDavid O'RiordanChemCIT,Dublin City Council,local authorities,wastewater,water
  Author: Sam Crowley BEng, MEngSc, MIEI, Crowley Services Ltd The fats, oils and grease (FOG) issue has received increasing publicity in recent years. Most recently, a 15 tonne wedge of solidified FOG was removed from a foul sewer at Kingston upon Thames, London in July. The appropriately named ‘fatberg’ incident received significant coverage...