Application of Sludge

Depending on the treatment type and quality, digested or stabilized sludge can be applied to public or private lands for landscaping or agriculture.

Sludge that has been treated (e.g., co-composted or removed from a planted drying bed, etc.) can be used in agriculture, home gardening, forestry, sod and turf growing, landscaping, parks, golf courses, mine reclamation, as a dump cover, or for erosion control. Although sludge has lower nutrient levels than commercial fertilizers (for nitrogen, phosphorus and potassium, respectively), it can replace them fully or in part. Additionally, treated sludge has been found to have properties superior to those of fertilizers, such as bulking and water retention properties, and the slow, steady release of nutrients.

Design Considerations

Solids are spread on the ground surface using conventional manure spreaders, tank trucks or specially designed vehicles. Liquid sludge (e.g., from anaerobic reactors) can be sprayed onto or injected into the ground.

Application rates and usage of sludge should take into account the presence of pathogens and contaminants, and the quantity of nutrients available so that it is used at a sustainable and agronomic rate (see also Reuse of Urine and Faeces in Agriculture).

Appropriateness

Although sludge is sometimes criticized for containing potentially high levels of metals or contaminants, commercial fertilizers are also contaminated to varying degrees, most likely with cadmium or other heavy metals. Faecal sludge from pit latrines should not have any chemical inputs and is, therefore, not a high-risk source of heavy metal contamination. Sludge that originates at large-scale wastewater treatment plants is more likely to be contaminated since it receives industrial and domestic chemicals, as well as surface water run-off, which may contain hydrocarbons and metals. Depending on the source, sludge can serve as a valuable and often much-needed source of nutrients. Application of sludge on land may be less expensive than disposal.

Health Aspects/Acceptance

The greatest barrier to the use of sludge is, generally, acceptance. However, even when sludge is not accepted by agriculture or local industries, it can still be useful for municipal projects and can actually provide significant savings (e.g., mine reclamation).

Depending on the source of the sludge and on the treatment method, it can be treated to a level where it is generally safe and no longer generates significant odour or vector problems. Following appropriate safety and application regulations is important. WHO guidelines on excreta use in agriculture (Volume IV) should be consulted for detailed information.

Operation & Maintenance

Spreading equipment must be maintained to ensure continued use. The amount and rate of sludge application should be monitored to prevent overloading and, thus, the potential for nutrient pollution. Workers should wear appropriate protective clothing.

References

Further Readings

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; SCHERTENLEIB, R.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies (Arabic). 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). PDF

    This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

  • Cover image of a reference book or miscellany.

    ANDREOLI, C.V. (Editor); SPERLING, M. von (Editor); FERNANDES, F. (Editor) (2007): Sludge Treatment and Disposal. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

    Sludge Treatment and Disposal is the sixth volume in the series Biological Wastewater Treatment. The book covers in a clear and informative way the sludge characteristics, production, treatment (thickening, dewatering, stabilisation, pathogens removal) and disposal (land application for agricultural purposes, sanitary landfills, landfarming and other methods). Environmental and public health issues are also fully described.

  • Cover image of a reference book or miscellany.

    HERSELMAN, J. E.; BURGER, L. W.; MOODLEY, P. (2008): Guidelines for the Utilisation and Disposal of Wastewater Sludge. Volume 5: Requirements for thermal sludge management practices and for commercial products containing sludge. Pretoria: Water Research Commission (WRC). URL. PDF

    Traditional practices related to wastewater sludge management include dedicated land disposal, waste piling, landfill disposal and, to a lesser degree, use in agricultural practices. However, due to varying reasons, on-site land disposal and waste piling have become the standard management options for many wastewater treatment plants in South Africa today. With sludge production increasing on a daily basis, it has however become apparent that current practices are unsustainable with sludge management becoming a problem for many municipalities in South Africa. Innovative solutions need to be sought to create opportunities that provide a wide spectrum of options to the management of wastewater sludge. This guideline aims to provide options and opportunities for this innovation and to encourage the beneficial use of wastewater sludge. Where wastewater sludge cannot be used as a resource, the guidelines also provide for its disposal in a responsible manner.

  • Cover image of a reference book or miscellany.

    KLINGEL, F. ; MONTANGERO, A. ; KONE, M.; STRAUSS, M. (2002): Fecal Sludge Management in Developing Countries - A Planning Manual. Duebendorf: Swiss Federal Institute for Environmental Science (EAWAG). URL [Accessed: 23.06.2010]. PDF

    This manual is a first approach to provide guidance on strategic planning of faecal sludge management. The study took place in the City of Nam Dinh, in Vietnam. The main principles for strategic sanitation planning have been adopted from the guide “Strategic Planning for Municipal Planning” from GHK Research and Training Ltd.

  • Cover image of a reference book or miscellany.

    MONTANGERO, A.; STRAUSS, M. (2004): Faecal Sludge Treatment. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 10.06.2010]. PDF

    This document reviews current practices of faecal sludge management and treatment.

  • Cover image of a reference book or miscellany.

    SPERLING, M. von (2007): Basic Principles of Wastewater Treatment. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

    Basic Principles of Wastewater Treatment is the second volume in the series Biological Wastewater Treatment, and focusses on the unit operations and processes associated with biological wastewater treatment. The major topics covered are: microbiology and ecology of wastewater treatment, reaction kinetics and reactor hydraulics, conversion of organic and inorganic matter, sedimentation, aeration.

  • Cover image of a reference book or miscellany.

    STRANDE, L. (Editor); RONTELTAP, M. (Editor); BRDJANOVIC, D. (Editor) (2014): Faecal Sludge Management. Systems Approach for Implementation and Operation. London: IWA Publishing. URL [Accessed: 16.07.2014]. PDF

    This is the first book to compile the current state of knowledge on faecal sludge management. It addresses the organization of the entire faecal sludge management service chain, from the collection and transport of sludge, to the current state of knowledge of treatment options, and the final end use or disposal of treated sludge. It presents an integrated approach that brings together technology, management, and planning, based on Sandec’s 20 years of experience in the field. It also discusses important factors to consider when evaluating and upscaling new treatment technology options. The book is designed for undergraduate and graduate students, engineers, and practitioners in the field who have some basic knowledge of environmental and/or wastewater engineering.

Case Studies

  • Cover image of a reference book or miscellany.

    ROBBINS, D.; STRANDE, L.; DOCZI, J. (2012): Opportunities in Fecal Sludge Management for Cities in Developing Countries: Experiences from the Philippines. North Carolina: RTI International . URL [Accessed: 15.01.2013]. PDF

    In July 2012, a team from RTI International deployed to the Philippines to evaluate four FSM programs with the goal of reporting on best practices and lessons learned. The four cases—Dumaguete City, San Fernando City, Maynilad Water for the west zone of metro Manila, and Manila Water from the east zone of metro Manila—were chosen to highlight their different approaches to implementing FSM.

Awareness Material

  • Cover image of a reference book or miscellany.

    ECOSAN CLUB (Editor) (2012): Faecal Sludge Management.. Vienna: Ecosan Club. URL [Accessed: 16.10.2012]. PDF

    This issue presents studies from different regions (Bangladesh, Cameroon, Burkina Faso) that mainly show the non-existence of faecal sludge management. Additionally, the last paper describes a new technological solution (LaDePa) for producing hygienically safe organic fertiliser from sludge from ventilated improved pit toilets (VIPs).

  • Cover image of a reference book or miscellany.

    KONE, D.; STRAUSS, M.; SAYWELL, D. (2007): Towards an Improved Faecal Sludge Management (FSM). Duebendorf: EAWAG/SANDEC. URL [Accessed: 15.12.2010]. PDF

    More than two billion urban dwellers in developing countries use on-site sanitation facilities such as pit latrines, septic tanks and aqua privies for excreta and wastewater disposal. Since on-site sanitation installations will serve the growing urban populations in developing countries for decades to come, increasing faecal sludge quantities will have to be managed. Proper faecal sludge management (FSM) is the important link missing in integrated urban sanitation upgrading efforts.

  • Cover image of a reference journal article.

    RULKENS, W. (2007): Sewage Sludge as a Biomass Resource. In: Energy & Fuels 2008 22, 9.URL [Accessed: 04.07.2012]. PDF

    The aim of this paper, which is based on a literature review, is to discuss the various options to recover energy from sewage sludge and to assess qualitatively these options with respect to the development stage, potential of energy recovery, and expected future developments. In this evaluation the effect of the presence of toxic organic and inorganic components in the sludge is also assessed.

Training Material

  • Cover image of a reference book or miscellany.

    EAWAG/SANDEC (Editor) (2008): Faecal Sludge Management. Lecture Notes. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 23.05.2012]. PDF

    This module pays special attention to the haulage, treatment and reuse or disposal of faecal sludge. It covers both technical and non-technical (socio-cultural, economic, political etc.) aspects and provides practical information on design, financing and planning of faecal sludge treatment plants.

  • Cover image of a reference book or miscellany.

    EAWAG (Editor); SANDEC (Editor) (2008): Faecal Sludge Management. Pdf Presentation. Duebendorf: Swiss Federal Institute of Aquatic Science (Eawag), Department of Water and Sanitation in Developing Countries (Sandec). URL [Accessed: 23.05.2012]. PDF

    A presentation about faecal sludge management in developing countries.