International Contrasts in Waste Water Management and Planning
Comparing regional strategies in Wastewater Treatment, from AMP cycles in UK to Tertiary Treatment in Spain and Morocco.
The world of wastewater management stands at a critical juncture, shaped by rising regulatory pressures, the urgent push for water reuse, and the ongoing challenge of optimizing major infrastructure investments.
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This essay builds on an in-depth conversation with Rafael Coca, a seasoned engineer specializing in wastewater process design across Spain, the UK, and Morocco.
His insights help illuminate the core complexities of the sector and the contrasting approaches taken around the world.
Wastewater may not sound appealing to everyone, but trust me—Rafael brings not only deep expertise but also a rare ability to explain complex processes in clear, engaging, “common language.”
He’s the kind of professional you don’t want to stop listening to when the conversation turns technical.
Back in 2015, I learned how a biological reactor truly works thanks to one of his outstanding masterclasses at our former company.
It’s absolutely worth listening to him.
Lack of water analytics
Perhaps one the most significant professional issues we as water professionals face is the lack of adequate analytical data provided by clients (yes, it sounds insane, but it is what it is), despite the demand for stringent effluent guarantees.
Rafa views the role of the process engineer as somewhat akin to a detective, needing full immersion in the client’s operational life to diagnose problems and propose solutions.
This ideal stands in sharp contrast to reality, where initial design data can be summarized in as little as three lines, while guarantees span several pages.
This ambiguity forces engineers to make critical design assumptions, often relying on analogical data from nearby potable water plants.
A simple, yet vital, parameter often missing is alkalinity, which is crucial for biological nitrification; insufficient alkalinity can halt the nitrogen removal process, yet clients demanding nitrogen reduction may not provide this foundational analytical information.
In one extreme case, a client issuing a desalination tender demanded that the supplier guarantee quality, production, and energy consumption, regardless of the quality of the incoming water.
This approach shifts all risk and uncertainty onto the design engineer while absolving the client of providing necessary foundational data.
International Approaches to Water Management
The conversation drew key comparisons between the water sectors in the United Kingdom, Spain, and Morocco, demonstrating varied priorities and planning strategies:
1. The UK and the 5-Year Horizon (AMP Cycles)
Rafa’s experience with Anglian Water in the UK provided a model of intensive collaboration.
Under the UK’s regulated, privatized system, projects are planned based on five-year cycles (AMPs, currently AMP8).
Engineers worked directly with the client (Anglian Water) within defined plans lasting five or six years.
Crucially, this system provided engineers with maximum detail, including full access to analytic data, flow rates, repair history, and even live SCADA control systems across the entire region.
This data accessibility allows for highly informed design and decision-making.
Furthermore, the UK approach favored a smaller, five-year project horizon, contrasting with traditional long-term planning.
This allowed for investment to be focused on immediate, specific needs, facilitating the use of standardized, modular, and prefabricated equipment to reduce time spent on site.
The short-horizon planning also enables significant synergy, allowing clients to secure better pricing by committing to purchasing specific equipment (like chemical dosing plants) for dozens of facilities simultaneously.
2. Morocco and the Priority of Tertiary Treatment
Morocco demonstrates a clear, strategic commitment to water reuse.
Rafa noted that approximately 90% to 100% of the wastewater projects his company has handled in Morocco over the last two and a half years have included tertiary treatment.
While effluent guarantees for nitrogen and phosphorus removal may be slightly less restrictive than those mandated by new European directives in Spain, the dedication to tertiary treatment is strong due to widespread reuse in agriculture and golf courses.
Political Control, European Funds, and Integrated Planning
A significant concern raised was the perceived lack of mature, integrated administrative planning in certain regions, particularly regarding projects driven by European funds.
Projects often appear in “waves” without a deep, prior analysis of necessity, leading to potentially misallocated public funds.
This lack of holistic analysis manifests when strict requirements, such as low nitrogen and phosphorus limits, are mandated without determining if that specific receiving water body is genuinely sensitive, or if the pollution burden derives more from agricultural run-off than from the wastewater treatment plant itself.
Similarly, investing in tertiary treatment may not be economically justified if there is no demonstrable demand for the regenerated water nearby.
Such non-integrated thinking fails to optimize resources, contrasting with how private businesses manage their capital.
The elimination of nitrogen and phosphorus is primarily achieved in the biological stage of treatment.
While biological treatment promotes P removal by encouraging bacteria to absorb phosphorus (which is then removed with sludge), reaching extremely low limits necessitates chemical addition.
This addition introduces operational costs (OpEx), requires managing reactive chemical use, and increases the overall production of sludge, impacting the size and cost of the sludge treatment line (thickening, dehydration, digestion).
The Tertiary Application Steps
Tertiary treatment follows the secondary treatment stage (which includes the biological reactor and secondary clarifiers) and serves two basic functions: Filtration and Disinfection.
1. Filtration
Filtration serves as a crucial pre-treatment step for disinfection.
By reducing suspended solids and turbidity, it removes physical barriers that decrease the effectiveness of subsequent disinfection steps.
Filtration is also a physical barrier against parasite eggs, such as those from nematodes, which is often a requirement for water reuse in irrigation.
Common filtration technologies were discussed with Rafa in our episode.
2. Disinfection
The primary method of disinfection used today is Ultraviolet (UV) radiation.
This is applied either in closed reactors or open channels.
While traditionally utilizing mercury amalgam lamps (fluorescent tube-like lights with a specific wavelength), emerging technology involves UV-LEDs.
However, this LED technology is not yet widely commercialized or commonly specified in standard bid documents.
Hypochlorite (chlorine) is also sometimes discussed as a disinfectant.
At present, advanced tertiary treatment (quaternary treatment) aimed at removing emergent contaminants like PFOA/PFAS using technologies such as ozone or activated carbon is not commonly seen in current projects in the region.
The Horizon Year: 25-50 Years?
The discussion also tackled the optimal time horizon for plant design.
Traditionally, large projects, including wastewater plants, were designed for a long-term horizon, often 25-50 years, based on projections of population and urbanistic growth.
However, this traditional approach is fraught with problems.
If the plant starts operating at a fraction of its design capacity (e.g., 40,000 m³/day when designed for 100,000 m³/day), the initial investment is inefficiently used.
Equipment may sit idle, depreciate, and potentially spoil before being needed, constituting a waste of public money.
The UK’s 5-year planning cycle offers a more efficient alternative, as per Rafa’s opinion. Though as we all know, UK’s water management is having also their problems…
By matching investment closely to current needs and near-term regulatory shifts, clients avoid overspending and ensure that the infrastructure deployed is modular and scalable.
This flexible, shorter-term approach better reflects the reality that regulatory requirements, such as phosphorus discharge limits, can change significantly within a short timeframe.
In essence, deciding the ideal horizon year is like choosing between building a mansion that will stand empty for two decades (the 25-year plan) or building a modular, expandable home that meets immediate needs efficiently and allows for smart, planned growth based on real-time data and regulatory changes (the 5-year/modular plan).
What I learned from visiting my local drinking water plant
A few weeks ago, I visited my city’s drinking water treatment plant with my colleagues from the Young Water Professionals Spain (Andalucía group).
Visiting my local drinking water treatment plant gave me a new appreciation for the complexity, precision, and constant innovation behind something we take for granted: turning raw reservoir water into safe, reliable drinking water every single day.
What seems simple from the outside is, in reality, a highly engineered sequence of chemical, physical and digital processes that must adapt continually to changing raw water conditions, new regulations, climatic challenges, and ever-evolving consumer demands.
1. Understanding the Treatment Process Behind Every Glass of Water
One of the first things I learned is that the plant actually operates with two independent intake points.
The plant’s preferred water source is the Minilla reservoir, not only for its better quality but also for its energy efficiency. Water from other sources requires pumping or additional treatment, which adds cost and complexity.
The core treatment process follows the classic sequence: coagulation, flocculation, decantation, and filtration.
Filtration is done mainly through sand filters, but the plant has recently diversified with activated carbon and other media to deal with emerging contaminants.
Finally, the water undergoes conditioning: pH correction (using lime-saturated water) and final disinfection, currently done with chlorine dioxide instead of traditional pre-chlorination to reduce trihalomethanes.
The level of thought that goes into something as simple as “keeping the pH stable” was interesting.
2. An Over-Dimensioned Giant With Energy Challenges
The plant was built for a much larger demand than today’s—10 cubic meters per second, of which only around 30% is currently used.
This is a clear example of what Rafa mentioned in our episode and had highlighted before.
This oversizing leads to operational challenges, especially in filtration and ozone dosing, where equipment often cannot run efficiently at such low loads.
One of the most surprising insights: a large portion of the plant’s energy consumption comes from carbon filters located at a high point—a design decision from older expansions. More than half of certain pumping energy is tied to this feature alone.
3. Real Operational Problems: Chemistry, Climate, and Compliance
Despite the sophistication of the plant, operators face very real challenges:
Hypochlorite quality is becoming a major issue, especially in summer when degradation accelerates and suppliers struggle to meet the stricter new limits on chlorates and chlorites.
This has led to installing refrigerated storage to slow down decomposition—something I never imagined was needed for “just chlorine.”
The plant regularly battles seasonal spikes of bromides, fluorides, manganese, iron, turbidity, and algae blooms.
And above all, they are working hard to comply with Spain’s new 2023 Water Quality Decree, which tightens many thresholds.
Problems like these show how dynamic water treatment really is: nothing stays constant, and operators must react almost daily to changing conditions.
4. Entering the Era of Digital Water
Another major takeaway is how rapidly the plant is evolving digitally. They are undergoing a full transformation—organizationally, technically, and technologically—under initiatives funded through European “Green Projects.”
Some of the innovations underway include:
41 digital transformation initiatives under the Digital Embassy 5.0 program
AI tools to support operator decisions on dosing, water sourcing, and process adjustments
Early development of a digital twin of the plant
Modernization of documentation, sensors, control systems, and process automation
This made me realize how water treatment is shifting from being purely chemical and mechanical to becoming data-driven, predictive, and increasingly optimized by algorithms.
5. Understanding Consumption Behavior and the Importance of Conservation
The plant team also monitors consumption patterns across the city in real time. I loved the anecdote that water demand dropped dramatically during the World Cup 2010 Final, simply because nobody opened a tap for 120 minutes!
The plant has led successful conservation initiatives, reducing average consumption to around 110 liters per inhabitant per day, with a goal to reach 90 liters under the city’s “Plan 90.” Compared to other Spanish cities consuming 150–160 liters, the progress is impressive.
What a complex business ours is—encouraging potential clients to consume less of our own product.
It’s a perfect example of how unique this industry is, and of why we must remain fully aware of its particular dynamics.
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