The El Harrach River, which flows through some of the most densely populated areas of Algiers, has for several decades become a symbol of the environmental challenges faced by rapidly urbanizing coastal cities. The foul odors that recur regularly are not only a nuisance for residents: they reflect a deep ecological imbalance, chronic pollution, and a deterioration of quality of life. Understanding the origins of these odors and proposing sustainable solutions requires an integrated analysis of the hydraulic, social, urban, industrial, and biological pressures exerted on this watercourse.
The Degradation of El Harrach River
For years, a significant share of domestic wastewater from Algiers’ neighborhoods, particularly those of Baraki, Hussein Dey, El Harrach, Bachdjerrah, and surrounding urbanized areas, was discharged directly or only partially treated into the river. These waters, rich in organic matter, decompose under the action of anaerobic bacteria, producing gases such as hydrogen sulfide, easily recognizable by its rotten-egg smell, ammonia, and other volatile organic compounds.
On top of this, industrial effluents were discharged for many years, as several facilities located in the river valley, from textiles to agri-food, as well as mechanical and chemical industries, released heavily loaded wastewater without adequate treatment. These effluents contain heavy metals, oils, fats, solvents, or complex chemical substances that further disrupt the ecosystem, promote anaerobic degradation of sediments, and intensify odor production. Sometimes, pollution comes from more distant areas, as the river begins in the Blida region, where no monitoring is conducted.
The decomposition of organic matter, amplified by the continuous deposition of solid waste, vegetation, plastics, food residues, and even animal carcasses, also contributes to accelerated fermentation. Added to this is the river’s physical configuration. The current is slow, often obstructed by sediments, waste, constructions, or insufficient infrastructure. This slowdown creates stagnant zones where dissolved oxygen drops significantly. The lack of oxygen favors anaerobic bacteria that produce gases such as methane, hydrogen sulfide, or mercaptans, all responsible for strong odors.
The sludge accumulated at the bottom of the river for years constitutes a true biological reactor where successive chemical and microbiological reactions continuously release foul-smelling gases. Climatic conditions further exacerbate the phenomenon: in summer, heat reduces oxygen solubility, accelerates fermentation reactions, and increases gas volatilization. Accelerated evaporation also concentrates certain pollutants locally.
Strategy to Restore El Harrach River
Faced with this situation, solutions must be addressed with a systemic logic. Sustainable improvement of the El Harrach River requires acting simultaneously on pollution sources, hydraulic dynamics, the biological quality of the environment, urban management, governance, and citizen involvement. A single isolated action, even an ambitious one, will not be sufficient. The top priority remains full control of domestic discharges. This means that the capacity of the Baraki wastewater treatment plant and associated sanitation systems must not only be maintained but strengthened. Wastewater must be collected, directed to appropriate treatment systems, and purified in accordance with international standards before being discharged or reused.
To prevent stormwater from overloading sanitation networks and bypassing treatment systems, it is also necessary to modernize the stormwater drainage network to strictly separate sewage from rainwater. This separation is essential to maintain treatment plant efficiency and limit accidental discharges into the river, particularly during heavy rainfall. Added to this are state investments, including river development works and the establishment of monitoring stations.
The second-dimension concerns industrial discharges. No lasting progress can be expected if industrial effluents are not fully controlled. Every industrial site in the river valley must have pre-treatment facilities meeting regulatory requirements. Monitoring must be intensified and conducted regularly, with a clear system of deterrent sanctions and support mechanisms for companies wishing to modernize their facilities. A complete, continuously updated mapping of industrial facilities and their discharges would make it possible to better target priorities. Industries must drastically reduce discharges of heavy metals, hydrocarbons, and complex organic compounds, as these substances do not degrade easily and strongly contribute to anaerobic reactions in sediments.
Water stagnation is another major challenge. Several actions are necessary to address it. The river’s natural flow must first be restored by removing physical obstacles, clearing obstructed sections, rehabilitating and recalibrating the riverbed, and reinforcing the banks while respecting ecological engineering principles. Dredging the sludge, particularly that accumulated over several decades, is essential, as these sediments are saturated with organic matter and pollutants responsible for continuous gas emissions. This dredging must be carried out in a controlled manner, with a system for managing polluted sediments to avoid their dispersion in the environment. Once the riverbed is restored, water circulation will become more fluid, naturally increasing oxygenation and reducing the formation of anaerobic pockets.
To reinforce these efforts, targeted aeration or oxygenation systems could be installed in critical zones, particularly where the current is naturally weak. Artificial oxygenation, used in several international urban rehabilitation projects, can drastically reduce odors by promoting less odorous aerobic decomposition. At the same time, the installation of vegetated filters, constructed wetlands, or retention basins can play a crucial role in improving biological water quality. These nature-based solutions help filter pollutants, stabilize banks, create habitats for biodiversity, and strengthen the environment’s self-purification capacity.
Managing solid waste is another essential component. Waste dumped in or near the river does more than pollute visually: it ferments, creates blockages, slows water flow, traps other organic materials, and promotes anaerobic decomposition. It is therefore essential to implement an integrated waste management strategy, including regular cleaning operations, the elimination of illegal dumping sites, strengthened control of sensitive areas, and extensive public awareness campaigns. Improving lighting, installing surveillance cameras, or establishing regulated nearby collection points can significantly reduce illegal dumping. Cooperation between local authorities, environmental associations, residents, and specialized companies will be essential to ensure long-term success.
Another fundamental issue is ecological restoration. The progressive renaturalization of the river, through the planting of species adapted to wetlands, the creation of ecological corridors, and the reintroduction of resistant aquatic fauna and flora, can not only enhance the site’s appearance but also strengthen its ecological resilience. Riparian vegetation plays a crucial role in natural filtration, soil stabilization, regulating water temperature, and improving aquatic habitats. Experiences in other major Mediterranean cities such as Barcelona or Marseille show that ecological restoration of an urban river can transform a degraded area into a true biodiversity corridor and recreational space for residents.
Scientific monitoring and governance are also indispensable pillars. Implementing a continuous monitoring system, based on sensors measuring dissolved oxygen, organic load, pollutant discharges, sediment composition, and gas emissions, would allow assessment of intervention effectiveness and adaptation of strategies. This system should be complemented by microbiological monitoring to identify the dynamics of anaerobic bacteria responsible for odors. An open digital platform would make data accessible to the public and encourage transparency, a crucial element for strengthening trust and citizen participation.
The success of such a project also requires a clear and coherent governance model. It is essential to coordinate interventions between the various stakeholders: the Ministry of Environment, Ministry of Water Resources, local authorities, the National Waste Agency, industrial managers, and associations. A unified steering structure, equipped with sufficient resources and a multi-year roadmap, would be best positioned to implement a coherent strategy. Past projects have sometimes suffered from a lack of coordination between institutions, which reduced the impact of investments. A strengthened regulatory framework, including strict discharge standards, monitoring mechanisms, and compliance incentives, will also be necessary.
Finally, the social and cultural dimension must not be overlooked. The El Harrach River flows through dense and vibrant neighborhoods, where the population can become a key player in transforming the site. Awareness campaigns, environmental education in schools, community cleanup programs, and citizen initiatives can help change behaviors. In several cities around the world, resident participation in reclaiming urban rivers has proven decisive.
Conclusion
The sustainable improvement of the El Harrach River will not rely solely on technical interventions, but on a comprehensive transformation combining sanitation, ecological restoration, integrated water management, industrial and environmental responsibility, citizen participation, modern governance, and transparency. By adopting a clear, ambitious, and coherent strategy, Algiers can transform this river,today perceived as a problem, into a true symbol of urban, ecological, and social renewal.
