Design and implementation of a treatment plant for the disposal of wastewater from portable toilets

Abstract

Characterization of wastewater from portable toilets show parameters values (i.e., Chemical Oxygen Demand COD and total suspended solids TSS) that exceed the limits stablished by environmental regulations. This means that a prior treatment of these effluents is mandatory. This paper describes the design and construction of a plant for the treatment of wastewater from portable toilets, in a coastal city with dry/humid tropical weather conditions. The plant has a capacity for the treatment of 2.2 m3 of wastewater every two days. The batch process for the treatment of wastewater from portable toilets consists of primary treatment (screening and sedimentation), secondary treatment (biological activated sludge) and tertiary treatment (disinfection by chlorination, and filtration with activated carbon and gravel filters), in order to eliminate the chemical disintegrator of organic matter, the blue color, bacteria and odors, and to meet the limit values in discharges at surface water bodies and public sewerage system. Cleaner production strategies were also implemented to improve the sustainability of the process, such as the use of recycled material (i.e. the empty containers of agents for organic material disintegration), use of unevennes in the land to decrease energy consumption, use of equipment (tanks and filters) from disused production units and substitution of the toilet disinfectant (which was formaldehyde based disintegrator), for a biodegradable and non-toxic glutaraldehyde-based disinfectant, considering the environmental commitment involved in wastewater treatment processes. The characterization of the treated water from the plant showed that it can be discharged into the sewer. A characterization of the microbia present in the bioreactor is suggested for future research and optimization of the wastewater treatment plant, since the inoculum identified in the process will be a potential adjuvant in other processes for organic material degradation such as septic tanks and wastewater treatment plants located in similar climatic conditions.