Wastewater expert and IWA Global Water Award 2021 winner Marcos von Sperling offers advice on providing new treatment in low- and middle-income countries, and the task of maintaining it.
In most low- and middle-income countries (LMIC), it is a real challenge to implement wastewater treatment. In urbanised areas with conventional piped sewerage systems, current statistics show that, in most countries, a high proportion of the population is still not connected to sewers. Adding to that scenario, the sewage flow that is collected by the network is frequently discharged untreated into water bodies. Improving these statistics is part of the Sustainable Development Goals, and involves a huge effort that needs to be addressed by low- and middle-income countries.
Improving the metrics in terms of percentage of population connected to sewers and percentage of wastewater treated is only part of the challenge, however. Yes, implementation of infrastructure must be celebrated, and the increase in coverage is undoubtedly essential, but it does not fully reveal the quality of the service being provided. In terms of wastewater treatment, implementing new treatment plants is a goal that does not bring an end in itself. On the contrary, new treatment plants unveil a list of new challenges that must be then faced by service providers, regulators and environmental agencies, as a whole.
The purpose of this article is not to present a negative view on a long list of challenges that need to be faced, but rather to act as an incentive for LMIC to go beyond simply inaugurating new treatment plants and consider that the mission has been accomplished, and to keep investing in their continued environmental and public health successes. Most of the issues are related to management, and technology availability is not usually a bottleneck in terms of sewage treatment.
The comments made here are personal, and based on my experience in Brazil, but I consider them to be also applicable to many other countries. The list is not exhaustive, and focuses only on municipal wastewater treatment in small to large towns that adopt off-site sewerage systems.
We could divide this discussion into two fronts. The first is related to the challenges to be faced when there is absence of wastewater treatment in a community or region. If there is success in this first stage through the implementation of treatment plants, then one needs to move on to a second stage, with the resulting challenges then associated with the existence of treatment plants in the region. Probably many LMIC will find themselves in a transitional stage, with several treatment plants needing to be implemented, while others are being planned, designed, built or put into operation.
Challenges dealing with the absence of treatment
The first obvious solution to the absence of wastewater treatment is to implement treatment plants. The main challenges here go beyond the question of having sufficient financial resources, which is typically referred to as the main obstacle in low- and middle-income countries. A sequence of tasks and activities needs to be well planned and executed, and if one of them is not done properly, it may jeopardise the whole implementation stage of new treatment plants. All this takes time, and skipping one stage to gain time or save money may lead to an unsuccessful outcome.
Challenges associated with the scenario of absence of wastewater treatment plants in urban areas in LMIC and the needs for their implementation are presented and discussed briefly below.
Obtain funding for implementing treatment plants. This is usually seen as the major challenge to be faced for implementing new treatment plants, but several other issues may be similarly important. Funding could be obtained at different stages and from different sources, but should cover the costs for conception, design and implementation of treatment plants (and, later on, for their operation and maintenance).
Reserve sufficient time and resources for making good conceptual reports to define treatment objectives and to decide about the treatment solutions to be adopted. Although this is of fundamental importance, with many aspects to factor in, preliminary conceptual studies have been frequently underrated. See the box ‘Adding new urban wastewater treatment: defining processes and objectives’ for more details.
Make good designs of the treatment plants. A good and flexible design is essential for a successful operation. Give importance not only to process design (sizing of units), but also to detailed design (hydraulic, civil, electromechanical, architectural, and so on).
Make good constructions of the treatment plants. Follow the design specifications, and only make adaptations if necessary and approved by the institutions involved. Avoid risky modifications from the design, aiming at purely saving money, because this could eventually lead to process failure. Use good material, and take into account the corrosive environment in the treatment plants.
Challenges with newly implemented urban treatment
Several challenges associated with the existence of wastewater treatment are summarised below. It should always be remembered that implementing new treatment plants does not guarantee success. The new challenges that appear in a scenario in which treatment plants have been implemented are sometimes forgotten, and, if there is no adequate long-term planning, unfortunately the treatment plants will not fulfil their objectives – and, in more extreme (and unfortunately frequent) cases, they will collapse and be simply abandoned.
Provide a good start-up of the new treatment plants. There is much expectation at the start of operation of a new treatment plant. The expected results will not be obtained immediately, and temporary malfunctioning may occur, but patience needs to be devoted to this stage, in order not to put at risk the quality of the treatment process selected and the concept of having sewage treatment at that selected location. Most likely, the town has spent decades discharging untreated wastewater, and it is entirely reasonable to wait for a few more months for things to be adjusted. Incoming loads to the treatment units must increase slowly and progressively during start-up, giving time for the biomass to develop. Assisted operation by the contractors during the start-up period, including staff training, is expected to alleviate the initial burden of having to deal with processes that may be entirely new to the local service providers.
Receive wastewater at the treatment plants. In many cases the coverage in terms of sewage collection is still small, and only small flows are collected and directed to the treatment plants, which have been designed for full capacity. In cases where coverage in terms of sewage collection is good, it may still be the case that the collected sewage is not conveyed to the treatment plant, because there are insufficient interceptor lines at the bottom of valleys – they are more difficult to implement than the sewerage network itself. In separate sewerage systems, reduce illegal connections of sewage into stormwater drainage systems and of stormwater into sewerage systems. In separate sewerage systems, avoid overflows due to the unwanted entrance of stormwater and power failure at pumping stations.
Guarantee proper functioning of the treatment units, equipment and installations. Ensure good maintenance infrastructure, which may be frequently scarce at LMIC, especially in small communities. Guarantee availability of spare parts and standby equipment, either locally or in nearby installations.
Guarantee a good operational level. Establish good training and capacity development of operational staff – this is frequently neglected in several situations in LMIC. Give value to the acquired knowledge of operators working in the treatment plants and incentivise them to develop and participate more in the decision on how best to operate the treatment units.
Monitor the treatment plant, and actually use the monitoring data. Perform monitoring, not only for legal requirements, but also as a support for plant management and control. Make good use of the monitored data – monitoring is not cheap. Flow measurements and water quality monitoring are scarce in several treatment plants. However, it is even more frustrating when monitoring exists, but the generated data are not used and interpreted.
Guarantee occupational safety of the operational staff. Ensure operational staff are protected by all safety measures, and that they are proud of the mission assigned to them.
Guarantee compliance with legal requirements for treatment plant performance. Quality standards may be in the form of discharge standards (applicable to the treated effluent) and water quality standards (applicable to the receiving water body). In either case, compliance with the legal requirements must be achieved. In LMIC, it is frequent to have standards that are very hard to comply with, because they have been simply copied from high-income countries. Try to establish a regulatory framework that conforms well with the local reality, while still giving sufficient protection to the environment.
Incorporate removal of pathogenic organisms, if necessary. Most treatment plants in LMIC incorporate only the objective of removing organic matter – BOD and COD. However, pathogens are a major concern in such countries, and due attention needs to be paid. Aim at having a universal sewage collection at the locality and full conveyance to the treatment plant, because discharge of even small amounts of collected but untreated sewage is likely to raise coliform or pathogen concentrations in the receiving water body. If necessary, depending on the water use (treated effluent or receiving water body), incorporate a disinfection stage.
If necessary, incorporate removal of nutrients (nitrogen and phosphorus). N and P removal is not trivial and requires the adoption of specific treatment processes. Therefore, the requirements for their removal should not be automatic in LMIC, and implemented predominantly in cases of discharge to sensitive water bodies.
Incorporate the removal of organic and inorganic micropollutants. These represent a more distant reality in LMIC. These countries need to be aware of the associated potential problems and follow up the development of new technologies of advanced treatment, but are likely to have difficulties in including this in their agenda at their earlier stages of sanitation infrastructure development.
Manage adequately the sludge produced. Sludge treatment and disposal are integral parts of wastewater treatment, and failure to take this into account will affect the overall environmental success of the system. Management of sludge in extensive treatment systems (e.g. stabilisation ponds and constructed wetlands), which have great potential in LMIC, involves actions taken at only long time intervals of years, but still they should not be neglected.
Manage adequately the biogas produced. Some treatment processes that involve an anaerobic stage produce biogas, which needs to be handled properly to avoid problems of bad smell, corrosion, occupational safety and greenhouse gas effects.
Reduce operational costs. If the plant is operating successfully, internal operational measures may be taken aimed at reducing costs, without sacrificing performance. The savings could be used to implement or improve sewerage infrastructure.
Expand treatment plants, if necessary. Population growth is important in many locations in LMIC, leading to an increase in the influent flows and pollutant loads over time. If the treatment plant becomes overloaded, its capacity needs to be increased, either by physical expansion or by implementation of operational control measures.
Guarantee safety and good relationships with the surrounding neighbourhoods. Try to treat the nearby population as partners, and not as problems. Participate at meetings with local representatives, and show the positive impacts that the treatment plant is bringing.
Include a focus of circular economy and resources recovery. Search for possibilities of using the treated liquid effluent (e.g., agricultural, urban, industrial reuse) instead of simply discharging it into a water body. Consider the produced sludge as biosolids, and search for a potential productive use (e.g., soil conditioner). In any application, comply with the regulations. Analyse the possibility of recovering elements or compounds considered as resources rather than pollutants: phosphorus, sulphur, metals, and biogas (energy). Avoid overly complex flowsheets for resource recovery that could not be handled well by the operational staff because of the increased complexity.
Provide institutional strengthening. All entities involved in the process (water and sanitation companies, environmental agencies, regulating agencies, population representation) must be strengthened and have common aims towards sustainability and environmental and public health protection.
Create a suitable environment for fostering applied research of appropriate solutions. Give incentives to local universities and research institutes to participate actively in the process, with a strong focus on applied research that addresses innovation, development and consolidation of appropriate technologies. Use the good experience from more developed countries, and try to adapt proven solutions to the local circumstances. Derive regional design guidelines based on successful operation of existing plants.
Both stages, related to the absence and to the existence of treatment plants, are associated with a long list of challenges. There is no single solution to approach all of them. Most possibly, success will be achieved if focus is not placed only on technology, but also, and very importantly, on management.
Low- and middle-income countries have to improve sanitation conditions, but this goes in parallel with several other demands from the population, related to provision of jobs, health system, education, personal safety, political stability and so many other issues that would make a list of challenges appear insurmountable.
The practical way is to move in a stepwise manner, achieving target after target, and always progressing in a positive direction. A dream may become reality, and the whole globe deserves that. •
Marcos von Sperling is a full professor at the Federal University of Minas Gerais, Brazil, and has worked for more than 40 years in the field of wastewater treatment. He is the author of several open-access textbooks published by IWA Publishing and is the recipient of the IWA Global Water Award 2021.
Adding new urban wastewater treatment: defining processes and objectives
When addressing the absence of wastewater treatment, it is important to reserve sufficient time and resources for making good conceptual reports to define treatment objectives and to decide about the treatment solutions to be adopted. There are many dimensions to this:
- Adopt suitable planning horizons (20 or 30 years), and perform population forecasts taking into account that growth rates in many LMIC are usually higher than in other countries. In order to accommodate for possible errors in the forecasts, consider implementing treatment plants in more than one phase, which could be adjusted in the future.
- Make good characterisations of the wastewaters to be treated (flows and pollutant concentrations) and investigate whether there will be additional loads (industrial wastewater, faecal and septic tank sludge, leachate from landfills and other sources). Take into account that sewage characteristics in LMIC may be different in terms of concentrations and per capita flows and loads.
- Use literature on wastewater treatment plant design suitable for LMIC, adapted to differences in wastewater composition and climatic conditions (temperature and rainfall regime) – several books and manuals are now freely available online.
- Decide on a centralised or decentralised setting for the treatment plants, based on population density, topography and layout of the sewerage network.
- Decide on the destination of the treated effluent (discharge to water bodies or reuse) and make the design to comply with legal requirements. Study the impact of the discharge into the water body.
- Decide on the treatment objectives: remove organic matter (as is most commonly done in LMIC), or also include nutrients and/or pathogens?
- Incorporate solutions for the treatment and destination of treatment products, such as sludge (biosolids) and biogas.
- Avoid adopting standard solutions for all localities – each solution should be site-specific.
- Avoid implementing directly imported solutions that have not been tested and endorsed locally. If they seem promising, carry out pilot studies before considering them for full-scale implementation.
- Try to adopt simple treatment processes, with little dependence on sophisticated electromechanical equipment and skilled operation. Consider using locally available material.
- Try to avoid possible impacts to the surrounding neighbourhood, and consider involving the population at early stages of treatment plant conception. Especially in small towns with decentralised solutions, population should participate in and contribute to the decision process.
- Strive for low-cost solutions, taking into account capital and operating expenditures.
Contributing reference works
Marcos von Sperling has published extensively with IWA Publishing. His books include the two-volume Biological wastewater treatment in warm climate regions (M von Sperling and CAL Chernicharo, 2005, DOI: 10.2166/9781780402734 and 10.2166/9781780402703), titles in the Biological Wastewater Treatment Series, and the recent Assessment of treatment plant performance and water quality data: a guide for students, researchers and practitioners (M von Sperling, ME Verbyla and SMAC Oliveira, 2020, DOI: 10.2166/9781780409320).
For more details, including various free/Open Access options, visit iwaponline.com and search and filter for eBooks by ‘von Sperling’.