Wastewater is a complex environment that is susceptible to a wide range of external influences leading to system variability. The dynamic nature of wastewater in both composition and inherent conditions adds another level of intricacy. Enzymes are pivotal in the removal of pollutants from wastewater so that the released end product meets the governing specifications. Developments in treatment technologies include utilising enzymes to degrade emerging micropollutants from wastewater such as bioactive chemicals (BACs). Understanding how enzymes respond to wastewater variability will allow for improved process adaption. Enzyme performance is often overlooked or the applied experimental conditions do not reflect a real wastewater treatment plant (WWTP).
Enzymes inherent to the wastewater system and exogenous enzymes proposed in BAC treatment technologies were simultaneously studied in this work. Investigating both types of enzymes provided an overarching conclusion on process and matrix conditions that impact on enzyme behaviour linked to wastewater treatment. This included pH, temperature, solids concentration, dissolved oxygen, conductivity and metal inhibition. Hydrolases were the inherent enzymes studied due to them being responsible for degrading the main bulk of the organic sewage load. Analysing the activities of five different hydrolases provided a metabolic indicator for accessing WWTP biological performance. Unique enzyme fingerprints were derived which identified temporal and spatial variability across the sampled WWTP. For example α-glucosidase activity in the activated sludge increased by 70% from the previous sampling day and the activity across the entire treatment process varied greatly. Laccase and tyrosinase are two exogenous enzymes that are regularly put forward as BAC treatment technologies due to their high promiscuity towards different substrates. Investigating the performance of these two enzymes by BAC removal at varying conditions relevant to a WWTP informs on enzyme behaviour to system variability and in turn pollutant removal.
The EU Watch List has a number of different BACs that must be continuously monitored. In this research the selected BACs to study laccase and tyrosinase performance were estrone (E1), diclofenac (DCF) and sulfamethoxazole (SMX) as they are known endocrine disrupting chemicals. To reflect the complex nature of wastewater the substrates are investigated as single and mixed solutions when treated with laccase or tyrosinase to identify any inhibitory or enhancing effects. Previous work had shown that SMX removal increased in the presence of E1 and DCF. The degradation of the substrates by the two enzymes will move from a clean water matrix to collected wastewater samples. Research in the literature mainly focuses on using buffered solutions to represent the wastewater matrix but this does not account for the daily change in feedstock. Process factors known to influence enzyme behaviour are currently being studied and the variability analysed but in ranges typical of a WWTP. The inherent enzyme research has already shown temporal and spatial variability in activity. Furthermore the enzymes are independent of each other as different trends in activity have been observed. Standard water quality parameters are taken whilst sampling and so the next stage is to correlate these parameters with enzyme activity to identify significant relationships.
Water contamination and water borne health risks have become crucial socio-economic issues in rural India. Due to over population and severe contamination of fresh water resources by toxic chemicals and pathogens, water related disease outbreaks are at their worst in the rural regions of India. Unfortunately, the existing household drinking water purification systems have many drawbacks such as high system cost, poor regeneration, energy consumption, complicated processes, treatment specificity, unfeasibility, ineffectiveness, etc., to ease implementation in the rural and remote areas. In the present study, activated carbon (AC) based potential, affordable and compact filters were prepared using low-cost, abundant and indigenous raw materials and active ingredients for potential treatment of the drinking water. The filters were designed in such a way that I should perform the multi-functionalities such as sorption, catalysis, disinfection and ion-exchange within the filter matrix for the sustainable and ease purification of drinking water. Locally synthesized AC using rice husk, coconut shells, etc., and the naturally available clay minerals were used as important raw-materials with active ingredients such as Ag, Cu, Ti, Fe, etc., to enhance the treatment potential. Natural clay collected from the local reservoirs was preprocessed and chemical compositions were analyzed. The results obtained showed that SiO2 and Al2O3 were dominated species, which act as potential adsorbents for removal of organic pollutants and other minor components such as Ca, Na, Mg, etc. The results also revealed that presence of about 10-12 wt of carbon contents and absence of any toxic elements in the natural clay. A known weight of clay, AC core ingredients and active agents with homogeneous mixed sequence were molded into different shapes such as disc, candle, & foam layer and converted into ceramic structures under high temperature (>1000°C). The produced filter materials were characterized by suitable analytical techniques to know the obtained properties, which influence water purification. The characterization results clearly showed that well crystallinity, structural elucidation and extensive morphology, higher porosity and surface area, higher stability, and durability in the filter materials, which apparently enhance the purification efficiency. The drinking water purification efficiency of carbon based filters was evaluated under the gravity using well designed filter setups. Partially contaminated water (D grade) was used and important water quality parameters, which effect on human health were considered for the study. The results obtained clearly indicated that carbon embedded ceramic filters achieved the required drinking water quality standards, which are fixed by the Bureau of Indian standards (BIS) within a short duration. Considerable purification efficiency by carbon filters could be attributed due to adsorption and partial ion-exchange nature of core ingredients, redox and disinfection processes of embedded active agents, which resulted in effective removal of pathogens and other pollutants in the water. Factors, which affect on the drinking water purification efficiency, such as mixing ration of filter materials, contact time, regenerability, gravity, additional pressure, etc., were studied and optimized for the real-time applications. The multi-functional properties, along with affordable sequences and feasibility for practical applications have made these carbon filters sustainable and an excellent compact drinking water facility for rural India.
Water quality has deteriorated globally and provision of clean water is one of the most important global concerns. Currently, several toxic organic and inorganic compounds have been found at critical levels in waste, ground and surface waters. Consequently, there is an imperative demand to develop robust and environmentally friendly methods to remove them from wastewater. In this regard, numerous physic-chemical treatment technologies have been reported to control/minimize water pollution. Adsorptive removal of toxic compounds using advanced porous materials is one of the most appealing approaches in wastewater treatment nowadays. In recent years, the metal-organic frameworks (MOFs), a subgroup of advanced porous nano-structured materials, due to their exceptional characteristics, are showing great potential for improved adsorption/separation of various water contaminants. In this work, we report a family of new zinc and copper MOFs based on diazo and oxim ligands that were synthesized solvothermally under conventional electric heating, using reported methods. In order to assess the effectiveness of synthetized MOFs in adsorption-related purposes, the materials were characterized with various techniques such as nitrogen adsorption and scanning electron microscopy (SEM). The adsorptive removal of hazardous materials from water is related to high surface area derived from their huge porosity; that make MOFs superior to other porous adsorbents for efficient adsorptive removal of hazardous compounds present in wastewater.
The purpose of prospective risk assessments for chemicals is to identify potential risks for humans or environmental compartments like water bodies prior to the use of the substances. This is an important element to reach the Sustainable Development Goal (SDG) 6.3 to minimize the release of hazardous chemicals and SDG 12.4 to achieve the environmentally sound management of chemicals. Only with the knowledge which emissions of hazardous chemicals are relevant, these can be reduced in a goal-oriented manner. Within our study, we challenged the environmental risk assessment for biocides, which is conducted under the European Biocidal Products Regulation 528/2012, and evaluated whether it covers all possible emissions of biocidal active substances from households into wastewater. Thereby, we identified possible limitations of the existing risk assessment concept and yet unidentified possible risks for wastewater treatment plants and receiving water bodies.
For this reason, we established inventories of household products that could possibly contain biocidal active substances in 131 households in selected study sites in Northern Germany. The products that were used in the households were registered with the help of a barcode scanner. The ingredients of these products were evaluated, whether they contained biocidal active substances and whether the specific use of these substances is falling under the Biocidal Products Regulation.
Biocidal active substances were present in all households, even though not all possessed biocidal products, as the majority of observations of biocidal active substances was in washing and cleaning agents and personal care products, but not in biocidal products. Around 64 % of the registered applications of biocidal active substances do not fall under the risk assessment of the Biocidal Products Regulation. These can be active substances present in washing and cleaning agents, which are not assessed or approved for the use as in-can-preservatives. Furthermore, all biocidal active substances present in personal care products are not covered by the risk assessment of the Biocidal Products Regulation.
The results show that gaps exist in the environmental risk assessment of biocidal active substances. The attempt to solve the problem would require an extensive increase of complexity of risk assessments and their aggregation throughout all legislation. From our point of view, a better approach to reduce possible risks by these substances in general would be to limit their use to in fact essential usages. A sustainable use of biocides should thus be promoted to account for the limitations in the environmental risk assessment of these substances. This could be a promising approach to reach the SDGs of minimizing the release of hazardous chemicals.