The synergistic transformation toward pollution and carbon reduction of the wastewater treatment sector, a key source of carbon emissions, is of strategic importance for achieving carbon neutrality. This paper systematically reviews emerging technologies that empower carbon neutrality in wastewater treatment, focusing on bioenhancement, resource recovery and energy self-sufficiency, novel functional materials, natural and hybrid systems, and digital synergistic coupling models, while clarifying the carbon-reduction mechanisms and application value of each technical pathway. The study found that bioenhancement reduces greenhouse gas emissions and energy consumption by revolutionizing microbial metabolic routes. Resource-recovery technologies convert organic pollutants into clean energy, driving treatment systems toward energy self-sufficiency while creating carbon-sink effects. Novel functional materials lower carbon-emission intensity by selectively capturing greenhouse gases and accelerating electron transfer. Natural and hybrid systems actively sequester carbon and regenerate energy through ecological cycling, and digital synergistic coupling transforms wastewater treatment plants from carbon emitters into carbon-asset producers via whole-process intelligent control. Currently, large-scale application of these emerging technologies is hindered by difficult microbial regulation, inadequate monitoring systems, lagging carbon-accounting standards, and an imbalance between economic cost and environmental benefit. Future efforts should coordinate technology R&D, policy mechanisms, and industrial ecosystems by strengthening functional-microbe regulation, building modular technology systems, and perfecting carbon-trading policies and green-finance instruments, thereby upgrading the wastewater treatment industry from a traditional energy consumer to a resource-output hub and offering a systematic solution for global carbon neutrality.
Odor emissions have become a critical bottleneck restricting the sustainable development of municipal wastewater treatment plants. Biological trickling filters (BTFs) are widely adopted because of their low energy consumption and ease of maintenance, yet their deodorization performance depends greatly on the characteristics of the packing material. Using bamboo charcoal as the control, this study systematically evaluated the deodorization performance of municipal sludge pyrolysis char (sludge char) as a BTF packing material and compared the removal efficiencies of NH3, H2S, and odor concentration under ambient (25℃) and relatively low (15℃) temperatures. Utilizing high-throughput sequencing analysis, the microbial mechanism of sludge char deodorization was revealed. The results showed that, the removal rates at 25℃ of NH3, H2S, and odor concentration by the sludge-char BTF reached 88.4%, 96.1%, and 87.8%, respectively, which were essentially equivalent to the rates of bamboo charcoal. When the temperature was decreased to 15℃, the deodorization efficiency of the sludge-char BTF was reduced by an average of 6.3% compared to that of bamboo charcoal. Furthermore, microbial analysis indicated that denitrifying sulfur-oxidizing bacteria enriched in the sludge char, such as Massilia and Microvirga, synergistically degraded odor components through the glutamate synthesis pathway driven by gln and glt genes, coupled with the sulfur-autotrophic denitrification pathway mediated by dsr and sox genes. The comprehensive analysis demonstrates that sludge char can replace high-cost bamboo charcoal as a BTF packing materia, providing not only a new perspective for low-cost deodorization in BTFs but also a novel approach for the resource utilization of municipal sludge.
As a stable nitrogen pollutant, nitrate is widely present in water, and high quantities can cause harm to the environment and to human health. Heterotrophic denitrification technology is commonly used in nitrogen-containing wastewater treatment because it is economical and efficient. The carbon source plays a very important role in this process as an electron donor. When the carbon source in the system is insufficient, an external carbon source needs to be added to ensure the denitrification effect. The denitrification rate of liquid carbon sources is high, because they can be directly used by microorganisms without hydrolysis or simple conversion, and the electron donor transfer is rapid, the path is simple, and the reaction speed is fast. However, the control accuracy is high, and excessive dosing can easily lead to excessive effluent DOC and secondary pollution. The denitrification rate of solid carbon sources is relatively low, and they need to be hydrolyzed or enzymatically hydrolyzed into small molecular organic matter before use. The carbon source is slowly released, and the electron donor transfer path is complex but more durable and stable, which can reduce the risk of carbon source waste and secondary pollution. In terms of microbial community, liquid carbon sources have a single component, which makes it easier for the microorganisms relying on these carbon sources to become the dominant flora and reduces community diversity. The carbon-release process of solid carbon sources is complex, which can enrich diverse functional bacteria and lead to higher community diversity. In terms of equipment and cost, liquid carbon sources need a high-precision control system, with high equipment costs; the solid-phase carbon-source process is simple and does not require complex dosing equipment. The price of natural materials is low; the cost of synthesizing polymers is high; and blockage problems may arise.
Agricultural non-point source pollution in plain river network areas originates from diverse sources and exhibits complex compositions. Although various governance practices have been implemented across regions, accurately selecting ecological control approaches suited to local characteristics remains a pressing challenge. Focusing on the Yangtze River Delta, this research systematically reviews regional experiences in agricultural non-point source pollution control through field investigations; and identifies three core approaches: in-field ecological transformation, pond-field integration, and agro-(forestry-)wetland complexes. To further verify their effectiveness, the study concentrates on pond-field integration and agro-(forestry-)wetland complexes by selecting Qingpu, Jiading, and Songjiang Districts of Shanghai as representative cases. By monitoring water quality before and after centralized treatment of farmland drainage, the reduction rates of major pollutant indicators were quantitatively assessed. The findings provide empirical data and practical reference for the systematic and precise control of agricultural non-point source pollution in the Yangtze River Delta, and offer valuable insights for selecting appropriate approaches in similar plain river network areas.
To address the spatial resolution limitations of water pollutant emission inventories, this study employed ArcGIS spatial analysis technology and adopted a bottom-up innovative accounting approach to minimize errors derived from allocating administrative-level emissions to spatial grids. A high-resolution water pollutant emission inventory system was developed across three-tiered grid, control unit, and watershed scales. Focusing on the Nanchuan River Basin, a typical Loess Plateau mountainous watershed, the study comprehensively detailed the compilation process of this spatially refined inventory. Emissions of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP) from various pollution sources were quantified, and the spatial emission characteristics of non-point and point sources were revealed through pollutant load per unit area statistics and kernel density analysis. The study produced several key findings: (1) The bottom-up accounting method proved feasible, establishing a grid-scale high-resolution emission inventory system that aligns with watershed ecological protection planning and partitioned environmental management needs, thereby supporting refined water environmental governance. (2) Point sources dominated pollutant emissions in the Nanchuan River Basin (contributing 69.72% of COD and 80.16% of TP), with large-scale livestock farming as the primary source (58.39% of total COD). (3) Rural and urban non-point sources were significant, jointly accounting for nearly one-fourth of COD emissions. (4) Emissions exhibited high spatial concentration along the mainstream of the Nanchuan River and the banks of the Dongchuan River. This inventory research and emission data robustly supported the “one city, one policy” initiative under the Joint Research on Ecological Protection and High-Quality Development in the Yellow River Basin, demonstrating substantial practical significance.
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