Domestic Wastewater Treatment: Brief Introduction & Case Study of Domestic Wastewater Treatment Project in Shandong Province

Domestic Wastewater Treatment:Source, Impacts, Contents and Treatment

Source of Domestic Wastewater

The surge in urbanization and the rapid growth in freshwater consumption for residential use are major contributors to water shortages, particularly in areas with limited water resources. Experts predict that global demand for freshwater will exceed supply by 40% by 2030. This indicates that the world is on the brink of a water crisis, as freshwater demand is projected to surpass supply by 40% by the end of the next decade.

Domestic wastewater,or residential wastewater contains used water from house and departments, mainly santitory wastewater, in addition to 90% water by weight, and various types of dissolved and pendulous substances such as nutrients, solids, pathogens, helminths, oils and greases, runoff from urban areas, heavy metals, and numerous toxic chemicals., run-off wastewater from the grounds.

Untreated sewage poses significant environmental and public health risks due to its diverse composition.

Contents of Domestic Wastewater

In the very first section of this case study, we provide an in-depth exploration of the potential dangers associated with untreated sewage.

Water and Nutrients

Untreated sewage comprises a significant amount of water, making it a carrier for various contaminants. It also contains nutrients like nitrogen and phosphorus, which can have detrimental effects on aquatic ecosystems when discharged into water bodies.

Solids and Organic Matter

The presence of solids, including organic matter, in untreated sewage contributes to the pollution of water sources. These substances can deplete oxygen levels in aquatic environments, resulting in the death of marine organisms and the disruption of ecosystems.

Pathogens

Untreated sewage is a breeding ground for pathogens such as bacteria, viruses, and protozoa. These microorganisms pose significant health risks, as they can cause waterborne diseases and infections when individuals come into contact with contaminated water.

Helminths

Untreated sewage may contain helminths, which are intestinal worms and worm-like parasites. These organisms can infect humans and animals, leading to various health complications and diseases. Oils, Greases, and Urban Runoff: Sewage often carries oils, greases, and runoff from streets, parking lots, and roofs. These substances can contaminate water bodies, adversely affecting aquatic life and contributing to the pollution of the surrounding environment.

Heavy Metals

Untreated sewage can contain heavy metals such as mercury, cadmium, lead, chromium, and copper. These toxic elements have detrimental effects on ecosystems, potentially leading to bioaccumulation and posing a risk to human and animal health.

Drabacks of Conventional Wastewater Treatment Methods & Introduction of AOPs

The presence of resistant molecules in wastewater streams has rendered conventional biological methods inadequate for complete effluent treatment. Consequently, the adoption of innovative technologies to convert wastewater into less harmful or simpler compounds that can be further treated biologically has become essential. Chemical oxidation technology is one such approach that employs chemical oxidants to convert pollutants into slightly toxic or harmless substances, making them more manageable. However, the degradation rates of chemical oxidation technologies, which utilize oxidizing agents like ozone and hydrogen peroxide, tend to be lower. As a result, advanced oxidation processes (AOPs) have emerged as promising technology for treating wastewater containing stubborn organic compounds. AOPs leverage the high reactivity of hydroxyl radicals to drive oxidation and effectively address the challenge of refractory organic compounds in wastewater treatment.

Electrochemical Advanced Oxidation Processes

Oxidants Generated in EAOPs  & Domestic Wastewater Treatment

In recent years, there has been a growing focus on developing more efficient techniques to address water contaminated with organic pollutants. Among these methods, electrochemical advanced oxidation processes (EAOPs) have gained significant attention. EAOPs have emerged as promising methods for the inactivation of microorganisms in water. EAOPs utilize electrochemical reactions to generate powerful oxidants, such as hydroxyl radicals (●OH). The generated ●OH radicals exhibit strong oxidative properties, effectively targeting and destroying refractory organic pollutants. These methods have demonstrated high efficiency in organic pollutant removal, making them a viable alternative for wastewater treatment.

By studying the composition and concentration of contaminants present in water sources, researchers can identify suitable scenarios and niche opportunities for electrochemically-driven technologies. This approach ensures the development of fit-for-purpose solutions tailored to specific water treatment challenges.

As the field of EAOPs continues to evolve, there are exciting prospects for further advancements. Research efforts should focus on refining the understanding of electrode scaling and fouling mechanisms, as well as exploring innovative reactor designs and electrode materials to enhance system efficiency and longevity. Additionally, collaboration between academia, industry, and regulatory bodies is essential to promote the adoption and implementation of electrochemical technologies for wastewater treatment on a larger scale.

Electrochemical advanced oxidation processes offer a promising avenue for effectively eliminating microorganisms in water. The application of EAOPs in water treatment shows great potential, but further investigations are necessary to address electrode scaling, fouling challenges, and the treatment of realistic water matrices.

Anodic Oxidation via Boron-doped diamond Electrodes

Boron-doped diamond (BDD) electrodes are exceptional nonactive electrodes that offer a range of unique characteristics. These include a wide potential window, high overpotential for O2 evolution, electrochemical stability, and extensive applicability for sensitive species detection. As a result, BDD electrodes are considered an ideal choice for the electrochemical mineralization of organic compounds. BDD anodes exhibit remarkable oxidation capacity compared to alternative electrodes even under relatively mild operating conditions.

With long-term stable performance and stability of EAOP systems based on Boron-doped diamond electrodes, complete organic pollutants removal from domestic wastewater become reality in industry scale .

Case Study of Domestic Wastewater Treatment Project

The study aims to address the treatment of more realistic water matrices, including their composition and concentration, to identify suitable applications and specialized opportunities for electrochemically-driven technologies.

Background and Brief Introduction To the Shandong Project

Location & Situation of the Project

The case is located in Zibo City, Shandong Province, which is a typical plain area with flat terrain and a temperate monsoon climate with an average annual precipitation of 640mm. there are no rivers and reservoirs near the village and it is a non-environmentally sensitive area. With about 330 resident households and a resident population of 1,220. The village has an area of 1715 mu(approximately 282.52 acres) of cultivated land, 170 mu (approximately 28 acres) of greenhouses.

Domestic Sewage Treatment & Turnout

In September 2019, a project was initialized to collect and treat rural domestic sewage. All the domestic sewage of 330 households in the village is collected and treated, taking the model of three-dimensional diversion of rainwater and sewage, a total of 11.3 Km of sewage collection pipe network is built, one sewage treatment station with a treatment capacity of 45 m³/d, and the effluent finally met the national standard  (DB37/3693-2019), and the effluent water is used for irrigation.

Domestic Sewage Wastewater Treatment Process

This area has a flat topography, a high degree of population aggregation, a good collective economy of the village, stable drainage, no municipal pipeline network, rivers or reservoirs around the village, the village has a large shed industry, suitable for the mode of centralized construction of sewage wastewater treatment facility.

Boromond technical team used technical process combining biological and anodic oxidation to avoid large power consumption then removing refractory organic pollutants.

Domestic Wastewater Treatment: Collection

The grey water generated from the kitchen and washroom of each household are connected to the collective pipes in the hutong using PVC pipes, finally collected and stored in the terminal sewage wastewater treatment station.

Rainwater and run-off wastewater pipes are located below the rainwater ditch, the multiple-layer collection system does not interfere with grey water collection system.

Domestic Wastewater Treatment Methods

Sewage wastewater treatment process adopts biological + BDD electrolyzer treatment process, biological treatment section adopts sedimentation and anaerobic process, BDD electrolyzer treatment section adopts high load of sewage wastewater influent through the lifting pump, so that the wastewater was processed within the Boromond CT7 eletrolyzer, an eletrolyzer which is designed to finish anodic oxidation process with BDD electrode as anode and Titanium as cathode material, in which the pollutants was degraded by some of the most powerful oxidant, for instance, hydroxyl radicals.

Data and Result

Field testing result recorded influent water with COD at 650 mg/L, SS up to 320 mg/L, TN at 70 mg/L and TP up to 2.5 mg/L, and there was a significant drop with major datas which reflects quality of the effluent water: COD at 120 mg/L, SS up to 15 mg/L, TN at 16 mg/L and TP up to 0.2 mg/L.

The process has the advantage of low energy consumption, energy consumption is reduced by more than 60% compared with the traditional process, taking the treatment capacity of 45m³/d as an example, the total installed power of the traditional process is about 5KW, the installed power of this technology is less than 2KW, the electricity consumption and energy consumption are greatly reduced, so it plays a significant role in energy saving and emission reduction.