Urea Treatment can be used on faecal sludge, blackwater or source separated urine and faeces. Urea, with the chemical formula CO(NH2), is used as an additive to create an alkaline environment in the sludge storage device and thereby helps sanitise the sludge.Mixture of urine, faeces and flushwater along with anal cleansing water (if water is used for cleansing) and/or dry cleansing materials. Blackwater contains the pathogens, nutrients and organic matter of faeces and the nutrients of urine that are diluted in the flushwater.Refers to (semi-solid) excrement that is not mixed with urine or water. Depending on diet, each person produces approximately 50–150 L per year of faecal matter of which about 80 % is water and the remaining solid fraction is mostly composed of organic material. Of the total essential plant nutrients excreted by the human body, faeces contain around 39 % of the phosphorus (P), 26 % of the potassium (K) and 12 % of the nitrogen (N). Faeces also contain the vast majority of the pathogens excreted by the body, as well as energy and carbon rich, fibrous material.Mixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies, i.e. it has not been transported through a sewer. It can be raw or partially digested, a slurry or semisolid, and results from the collection and storage/treatment of excreta or blackwater, with or without greywater. Wastewater sludge (also referred to as sewage sludge) originates from sewer-based wastewater collection and (semi-)centralised treatment processes. The sludge composition will determine the type of treatment that is required and the end-use possibilities.The liquid produced by the body to rid itself of nitrogen in the form of urea and other waste products. In this context, the urine product refers to pure urine that is not mixed with faeces or water. Depending on diet, human urine collected from one person during one year (approx. 300 to 550 L) contains 2 to 4 kg of nitrogen. The urine of healthy individuals is sterile when it leaves the body but is often immediately contaminated by coming into contact with faeces.Describes technologies for on-site collection, storage, and sometimes (pre-) treatment of the products generated at the user interface. The treatment provided by these technologies is often a function of storage and is usually passive (i.e. requires no energy input), except a few emerging technologies where additives are needed. Thus, products that are ‘treated’ by these technologies often require subsequent treatment before use and/or disposal. In the technology overview graphic, this functional group is subdivided into the two subgroups: “Collection/Storage” and “(Pre-)Treatment”. This allows a further classification for each of the listed technologies with regard to their function: collection and storage, (pre-) treatment only or both.Refers to the methods through which products are returned to the environment, either as useful resources or reduced-risk materials. Some products can also be cycled back into a system (e.g. by using treated greywater for flushing).A functional group is a grouping of technologies that have similar functions. The compendium proposes five different functional groups from which technologies can be chosen to build a sanitation system:
User interface (U), Collection and Storage/Treatment (S), Conveyance (C), (Semi-) Centralised Treatment (T), Use and/or Disposal (U).
A sanitation system is a multi-step process in which sanitation products such as human excreta and wastewater are managed from the point of generation to the point of use or ultimate disposal. It is a context-specific series of technologies and services for the management of these sanitation products, i.e. for their collection, containment, transport, treatment, transformation, use or disposal. A sanitation system comprises functional groups of technologies that can be selected according to context. By selecting technologies from each applicable functional group, considering the incoming and outgoing products, and the suitability of the technologies in a particular context, a logical, modular sanitation system can be designed. A sanitation system also includes the management and operation and maintenance (O & M) required to ensure that the system functions safely and sustainably. The utilisation of products derived from a sanitation system.
Any substance that is used for growth. Nitrogen (N), phosphorus (P) and potassium (K) are the main nutrients contained in agricultural fertilisers. N and P are also primarily responsible for the eutrophication of water bodies.
A sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated.
An organism or other agent that causes disease.The means of safely collecting and hygienically disposing of excreta and liquid
wastes for the protection of public health and the preservation of the quality of public water bodies and, more generally, of the environment.

Waste matter that is transported through the sewer.
An open channel or closed pipe used to convey sewage. See C.3 and C.4
The organic molecule (NH2)2CO that is excreted in urine and that contains the nutrient nitrogen. Over time, urea breaks down into carbon dioxide and ammonium, which is readily used by organisms in soil. It can also be used for on-site faecal sludge treatment. See. S.18Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

Urea when added to faecal sludge is catalysed by the enzyme urease, which is present in faecal material, to decompose into ammonia and carbonate. The urea decomposition results in an alkaline pH (above 7) affecting the equilibrium between ammonia and ammonium, favouring the formation of ammonia. The un-ionised ammonia (NH3) acts as the main sanitising agent. Pathogen inactivation by uncharged ammonia has been reported for several types of microorganisms, bacteria, viruses and parasites. Ammonia disinfection has been shown to be effective in urine, sewage sludge, and compost, but applications for faecal sludge are still in the research phase. The process depends on temperature and partial pressures of ammonia gas above the liquid. Hence, ventilation and head space also influences the process conditions. It is recommended that treatment is undertaken in a sealed vessel to minimise the amount of ammonia gas that escapes and to force the equilibrium towards soluble ammonia. The treatment should be done as a batch process to ensure consistent sanitisation in the sludge.

Design Considerations

Urea is usually added at a ratio of 2 % of the overall sludge wet weight. Urea is initially placed in the storage vessel (e.g. bladder/closed tank) and then faecal sludge is pumped into the vessel. The size of the vessel may vary depending on the amount and frequency of the sludge to be treated. A pump is used to circulate the sludge within the storage vessel to ensure adequate contact between the urea and sludge. Urea decomposition requires a minimum of 4 days, hence a retention time in the closed vessel of approximately 1 week is recommended.

Materials

Urea Treatment needs a lockable vessel (e.g. a closed tank or portable bladder) and a recirculation pump to achieve a homogeneous sludge- urea mix. For liquid sludge, a diaphragm pump may be used, whereas thicker sludge may need a screw pump or a vacuum pump. In addition, a steady supply of urea is needed. Urea is a conventional, widely used and affordable chemical fertilizer that should be available in most local contexts. In addition, a water testing kit (particularly for pH and E. coli) is needed to control pH levels in the urea sludge mix and to test the level of treatment efficacy.

Applicability

Urea Treatment is considered an emerging technology that has not been widely used yet in emergency settings. However, first pilot projects and studies are promising and growing evidence suggests that Urea Treatment may be a suitable treatment option for the acute emergency phase due to its short treatment time (around 1 week), a relatively simple process and use of readily available materials.

Operation and Maintenance

Regular maintenance of pumps used for mixing is required. Due to potential health risks when handling urea (see below) the process requires skilled personnel following health and safety protocols and wearing proper personal protective equipment (PPE).

Health and Safety

Urea may be hazardous when it comes on contact with skin or eyes (irritant), ingestion or inhalation and may be combustible at high temperatures. Ammonia gas is toxic and precautions are needed when removing sludge from the tank. PPE (for example masks, gloves, aprons and long-sleeved clothing) must be worn when handling urea to prevent irritation to eyes, skin, and the respiratory system.

Costs

Urea Treatment is a relatively cheap treatment option. Costs may vary depending on the availability and costs of local materials and urea. To treat 1 m3 of faecal sludge, 20 kg of urea are required and urea is generally available and affordable.

Social Considerations

Appropriate health and safety protocols must be in place and include the provision of PPE and trainings for involved staff.