Domestic Sewage Treatment Plant Research Articles

Avaliação da eficiência do tratamento combinado de lixiviado de aterro sanitário e esgoto doméstico utilizando ozônio

The objective of this work was to evaluate the efficiency of the combined treatment of leachate from the Sao Leopoldo landfill with the domestic sewage treatment plant of the Sinos Valley University (UNISINOS) by means of Advanced Oxidation Processes, with addition of ozone (O3). Two experiments were carried out, in which 100 liters of effluents were treated in each of them, testing two proportions of leachate in the sewage, of 2% and 5%, which are common in ETP that operate combined treatments. The following parameters were monitored: Chemical Oxygen Demand, Biochemical Oxygen Demand, Apparent and True Colors, Turbidity, Total Nitrogen, Total, Organic and Inorganic Carbons and pH. The first test with a mixture of 2% of leachate with domestic sewage presented viable treatment, with mean removals of BOD and COD of 90% and 91%. Removals of apparent color (92%) and true (98%) were also obtained. As the concentration of leachate in the sanitary sewage increased (5%), some evaluation parameters, mainly total nitrogen, turbidity and COD, were significantly affected. The results obtained in this study suggest that the concentration of 2% of leachate is the best indicated for the combined treatment of domestic leachate and sewage. Keywords: Leachate, Advanced oxidative processes, ozone.

Behavior of Micropollutants in Polishing Units that Combine Sorption and Biodegradation Mechanisms to Improve the Quality of Activated Sludge Effluent

The current study evaluated the removal of six micropollutants (estrone (E1); 17β-estradiol (E2); 17α-ethynylestradiol (EE2); ibuprofen (IBP), diclofenac (DCF), and paracetamol (PCT)) from the final effluent of an activated sludge domestic sewage treatment plant using polishing filters. Four polishing filters were assembled as columns and filled with a mixture of sand and vermiculite, sand and charcoal, sand and granulated activated carbon (9:1 by volume), and sand only. The column filters were placed near the outlet of a full-scale activated sludge treatment plant and were fed with a treated effluent containing from 4.71 to 28.93 ng L-1 of the target compounds at a hydraulic loading rate (HLR) of 50 m3 m−2 day−1. Samples were collected periodically from the influent (biologically treated sewage) and effluent of the four columns and analyzed for estrogens, anti-inflammatories, and analgesic compounds. Liquid samples were submitted to a solid phase extraction (SPE) and analyzed by gas chromatography coupled with mass spectrometry after their derivatization. Among the compounds found, diclofenac was distinguished by the high occurrence of detection in the samples (85%) and higher mean concentration (~ 17 ng L−1). High removal efficiency (> 90%) of the estrogens was observed in the polishing systems studied, while for the other targets, the removal efficiency varied from 10 to 30%. The concentration values of some compounds were low, probably due to rainfall during the sampling period.

IDENTIFICATION OF PHARMACEUTICAL RESIDUES IN TREATED SEWAGE EFFLUENTS IN JOHOR, MALAYSIA

The introduction of pharmaceutical residues into aquatic environment has threatened the livelihood of aquatic organisms worldwide. The entrance of these residues into the environment originates from sewage effluents discharged from domestic wastewater treatment plants. Up to date, their presence in the sewage effluent is not monitored in Malaysia. Therefore, this study aims to identify the presence of pharmaceutical residues in the effluent domestic sewage treatment plants employed in Johor Bahru, Malaysia. Briefly, ten pharmaceutical compounds, including acetaminophen, sulfathiazole, sulfamethazine, sulfamethoxazole, clarithromycin, trimethoprim, lincomycin, carbamazepine, naproxen and ibuprofen, were selected based on their worldwide consumption. Sewage samples from five different types of sewage treatment system were collected. The samples were filtered prior to solid-phase extraction. Finally, the extracted samples were analysed with LC-MS/MS. The analyses showed that only sulfathiazole was not present in all effluent samples. Acetaminophen recorded the highest concentration of 9299 ng/L in an Imhoff Tank. Meanwhile, the lowest concentration of pharmaceutical residue detected was sulfamethazine, i.e. 0.843 ng/L, in a sequencing batch reactor. Overall, six out from ten pharmaceutical residues were found in all sewage samples denoting the inefficiency of current biological treatment systems in removing trace pharmaceutical compounds from sewage.

Research on the sewage treatment in high altitude region based on Lhasa Sewage Treatment Plant

Sewage treatment is of great significance to enhance environmental quality, consolidate pollution prevention and ecological protection, and ensure sustainable economic and social development in high altitude region. However, there are numerous difficulties in sewage treatment due to the alpine climate, the relatively low economic development level, and the backward operation and management styles, etc. In this study, the characteristics of influent quality in the sewage treatment plant in Lhasa are investigated by analysing the influent BOD5/COD and BOD5/TN, comparing key indexes recorded from 2014 to 2016 with the hinterland. Results show that the concentration of influent COD, BOD5, NH3-N and SS in the Lhasa sewage treatment plant, in which the sewage belongs to low-concentration urban sewage, is smaller than that in the domestic sewage treatment plants in the mainland. The concentration ratio of BOD5/COD and BOD5/TN is below 0.4 and 4, which indicates that the biodegradation is poor and the carbon sources are in bad demand. The consequences obtained play a vital role in the design, operation and management of sewage treatment plants in high altitude region.

Activated Sludge Mineralization and Solutions in the Process of Zero-Valent Iron Autotrophic Denitrification

We studied the inoculation of activated sludge from domestic sewage treatment plants. The reaction of reducing nitrate by zero-valent iron was started in the up-flow anaerobic reactor. After 52 d of operation, a nitrogen removal rate of 29.3 g·(m3·d)-1 was achieved. Ferric iron and iron oxide coated on the sludge formed in the operation process caused the mineralization and slowly decreased the sludge activity. The methods of the "supplement and replacement of the sludge in the reactor" and "changing the reflux mode of the reactor" were applied. Using the method of the supplement and replacement of the sludge in the reactor, by discharging a part of the sludge in the reactor and adding the extra dosage from the anaerobic denitrifying sludge for the treatment of wastewater, after 22 d of operation, the conversion rate of nitrate-nitrogen was 33.0 g·(m3·d)-1 and the concentration of nitrite-nitrogen was 16.50 mg·L-1. The effluent average concentration of ammonia-nitrogen decreased from 12.38 mg·L-1 to 3.58 mg·L-1 and the nitrogen removal rate was recovered from 9.9 g·(m3·d)-1to 15.0 g·(m3·d)-1. The biological reaction weakened the chemical reduction of nitrate by zero-valent iron. Using the method of changing the reflux mode of the reactor, the reflux tank was arranged outside the reaction column using hydraulic circulation. The increase in the erosion of the upper layer of the sedimentation tank would bring out ferric iron and iron oxide with the outflow water and they would be deposited in the reflux tank. The corresponding ferric iron of transformation of nitrate settled in the external reflux tank was 58% at the ascending velocity of 3.49 m·h-1. The nitrate-nitrogen conversion rate was 34.3 g·(m3·d)-1, the effluent concentration of nitrite-nitrogen was 0.22 mg·L-1, and ammonia-nitrogen was 0.75 mg·L-1. Ammonia and nitrite did not extensively accumulate. The nitrogen removal rate was 33.4 g·(m3·d)-1, which solved the problem of the mineralized sludge in the long-term reactor operation. In summary, the method of reforming the reflux mode of the reactor performed better than the method of the supplement and replacement of sludge in the reactor.

Evaluation of virus recovery methods and efficiency of tannin-derived coagulants in removing total coliforms, E. coli and enteric viruses in effluents of a domestic sewage treatment plant.

In the present study, nine coagulants having potential to be used for sewage treatment were compared to assess their efficiency in removing total coliform bacteria, Escherichia coli and adenovirus. The coagulants tested were metallic and organic and their efficiency was compared when treating samples of raw and treated sewage (activated sludge). Before the efficiency tests of the coagulants, viral concentration methods were compared. Coagulation tests were carried out by using the jar-test system and the doses used ranged from 100 ppm to 1,000 ppm. Viral DNA was extracted and subjected to real-time polymerase chain reaction (qPCR) using primers for the gene of AdV hexon. Aluminum sulfate (1,000 ppm) presented the best results for raw sewage among metal coagulants whereas Acquapol® C118 and WW (1,000 ppm) had the most satisfactory results among organic coagulants, both reducing up to 7 logs for coliforms and 4 logs for virus. For the treated effluent, FeCl2 (1,000 ppm) presented best results for metal coagulants, whereas, from organic coagulants, the best removal rates were for Acquapol® 893/11 (1,000 ppm), both reducing up to 3 logs for coliforms and 4 logs for virus.

Biological Waste Water Rehabilitation of Sugar Factories by Algocoenosis Correction

The article deals with theoretical and practical aspects of biological waste water rehabilitation of sugar factories by algocoenosis correction. This technology allows you to transfer domestic sewage treatment plant of filtration mode fields in the biological treatment ponds mode, significantly reducing the area of sewage treatment plants, thus improving the quality of treated waste water, which will, in turn, use them repeatedly reducing total water consumption.

Domestic sewage treatment plant or ecological septic tank

Domestic sewage treatment plant or ecological septic tank

Carbon sequestration potential in domestic sewage treatment plants of Indian cities

Carbon sequestration is a new technology that is gaining importance in combating the harmful effects of global warming. The potential for carbon sequestration from domestic sewage treatment plants operating in India was studied. Based on the data provided by the Government of India on the generation of domestic sewage by State, the organic load generation, sequestration potential and net release of CO2 were calculated. By going in for carbon sequestration, domestic sewage treatment in India has a potential to be a carbon neutral sector with a capacity to store 22 thousand tonnes of CO2 every day at current levels.The Government of India's focus is on increasing the share of renewable energy sources to combat emissions; however, carbon sequestration technology would be an ideal solution for deployment over the time period required for renewable energy' share to become significant. Three metro cities, viz., Delhi, Mumbai, and Chennai are immediate prospects that could adopt this technology, followed by other cities. The prevalent Renewable Energy Credit Trading Scheme in India can support carbon sequestration technology infusion. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 162–170, 2017

454-Pyrosequencing analysis of highly adapted azo dye-degrading microbial communities in a two-stage anaerobic–aerobic bioreactor treating textile effluent

ABSTRACTAzo dyes, which are widely used in the textile industry, exhibit significant toxic characteristics for the environment and the human population. Sequential anaerobic–aerobic reactor systems are efficient for the degradation of dyes and the mineralization of intermediate compounds; however, little is known about the composition of the microbial communities responsible for dye degradation in these systems. 454-Pyrosequencing of the 16S rRNA gene was employed to assess the bacterial biodiversity and composition of a two-stage (anaerobic–aerobic) pilot-scale reactor that treats effluent from a denim factory. The anaerobic reactor was inoculated with anaerobic sludge from a domestic sewage treatment plant. Due to the selective composition of the textile wastewater, after 210 days of operation, the anaerobic reactor was dominated by the single genus Clostridium, affiliated with the Firmicutes phylum. The aerobic biofilter harbored a diverse bacterial community. The most abundant phylum in the aerobic biofilter was Proteobacteria, which was primarily represented by the Gamma, Delta and Epsilon classes followed by Firmicutes and other phyla. Several bacterial genera were identified that most likely played an essential role in azo dye degradation in the investigated system.

溧阳重点流域污染源解析研究

流域源解析可为水环境综合整治提供依据。本文采用调查和数学模型估算溧阳重点流域内点源和面源的典型水污染物的排放量和贡献率。结果显示，渔业养殖、种植农村生活污水和污水厂是溧阳主要的水污染源。工业排放的污染物虽然贡献率较小，但是从2011到2013有逐年增加的趋势。种植业的总氮、总磷排放量分别占溧阳排放总量的46.24%和46.88%。渔业养殖排放的COD、总磷分别占溧阳排放总量的26.01%和40.83%，且排放贡献率有增加的趋势。点污染源排放的COD、氨氮、总氮、总磷的贡献率分别为37.12%，44.02%，21.30%和7.63%，而面源的相应污染物的贡献率分别为62.88%，55.98%，78.70%和92.37%。对面源的管理控制措施是溧阳水环境整治的重点。 Source apportionment can provide the basis for comprehensive improvement of water environment. Based on the investigation and mathematical model, this paper estimated water pollutants emission and contribution from point source and non-point source in the key rivers of Liyang city. The results show that: the fishery, rural domestic sewage and city sewage treatment plant are the main water pollutant sources. The contribution of water pollutants from industrial emission source is small and the water pollutants emission from is increased from 2011 to 2013. The loss of the total nitrogen and total phosphorus from farmland accounted for 46.24% and 46.88% respectively. The loss of COD and total phosphorus from fishery accounted for 26.01% and 40.83% respectively and the pollutant contribution kept increasing. The contribution of COD, ammonia nitrogen, total nitrogen and total phosphorus from point source is 37.12%, 44.02%, 21.30% and 7.63%, and from non-point source is 62.88%, 55.98%, 78.70% and 92.37%, respectively. As a result, the management of non-point source is more important than that of point source.

Indicators of the environmental aspect of spatial order as a tool for the environmental protection in suburban areas

The spatial range of the present analysis spans the rural and urban communities of Lower Silesia region. The aim of the study was to determine the needs in terms of environmental protection and development, due to environmental resources and equipment in the communal infrastructure. The environmental aspect of spatial order was evaluated. It was assumed that the implementation of the spatial order in the aspect of the environment is done by means of developing that environment, and especially by the presence / absence of the biotic (natural) elements and the presence / absence of technical infrastructure (utilities), as well as the proper use thereof. Analyses were performed using the following indicators: the share of protected areas in the total area of the community, the share of green areas in the total area of the community, forestation rates, share of the population using sewage system in the general population of the community, number of domestic sewage treatment plants and number of septic tanks per 1000 inhabitants, as well as the total municipal waste per capita. Rural and urban communities were compared. The data was obtained from GUS (Central Statistical Office), the local data bank. The results allowed for ranking the communities included in the study according to a hierarchy, and grouping them in the terms of spatial order in the environmental aspect.

Mass loading and removal of pharmaceuticals and personal care products, including psychoactive and illicit drugs and artificial sweeteners, in five sewage treatment plants in India

Despite the high consumption of pharmaceuticals, mass loading and removal of these compounds in sewage treatment plants (STPs) in India have not been investigated. In this study, 43 pharmaceuticals and personal care products as well as 13 of their metabolites were analyzed in five domestic STPs (wastewater influent, effluent, and sludge) and in raw domestic sewage collected in open sewerage channels in residential areas in India. The mean concentrations of amphetamine in two of the five STPs (mean: 4300ng/L and 4720ng/L) were the highest ever reported for wastewater influents, globally. Among artificial sweeteners, saccharin was the most abundant compound in influents (mean: 303,000ng/L, df: 100%), followed by cyclamate [3460ng/L, detection frequency (df): 75%] and sucralose (1460ng/L, df: 100%). Elevated mean concentrations of an antimicrobial (triclocarban=6180ng/L), analgesic (ibuprofen=2320ng/L), antihypertensive (atenolol=3180ng/L), illicit drug (amphetamine=984ng/L), and saccharin (419,000ng/L) were found in the Cooum River in Chennai. The median removal efficiencies of pharmaceuticals and personal care products (PPCPs) ranged from 5% (norcocaine) to 100% (triclosan) for the five STPs. On the basis of the concentrations measured in influents, the mass loadings of PPCPs were estimated to range from 0.1 (norquetiapine) to 77,800 (saccharin) mg/d/1000 people. An estimated 2.55kg of triclocarban, 3.24kg of carbamazepine, 6.93kg of amphetamine, and 252kg of saccharin were discharged from a typical STP with an average flow rate of 20.7 million liters per day (serving a population of 325,000) in India.

Improvement of nitrification in winter using dewatering water

The reject water from the bioreactor of a domestic sewage treatment plant consists of supernatants of the anaerobic digestion tank and sludge thickener and dewatering water, which account for about 1–3% of the wastewater influent flow rate. Among these, dewatering water is very beneficial as it makes nitrification bacteria the dominant micro-organisms due to their higher nitrogen concentration and alkalinity, and their lower suspended solid, compared to those of the digester supernatant. This study was designed to improve the efficiency of nitrification in winter. Toward this end, the number of nitrifying micro-organisms was increased using dewatering water in the nitrification tank, and then they were introduced into the aeration tank to investigate the nitrification trends before and after the introduction. A comparative experiment was conducted at 12.5°C with an aeration tank having a capacity of 20 m3/d. The results showed average NH4+–N concentrations of the treated water of 8.5 and 18.4 mg/L in the pilot plant and the sewage treatment plant, respectively, and average NO3−–N concentrations of the treated water were 24.3 and 6.0 mg/L, respectively, which revealed nitrification improvement with the injection of dewatering water. The results of the microbiological analysis showed 3.27% total nitrification bacteria in the aeration tank of the pilot plant and 1.28% in that of the wastewater treatment plant, which indicate that the winter nitrification improved in the pilot plant.

Cadmium removal from aqueous solutions via biosorption onto acclimatized activated sludge

AbstractEquilibrium and kinetics of Cadmium (II) biosorption onto acclimatized activated sludge (AAS) were studied. Activated sludge (AS) obtained from a domestic sewage treatment plant was acclimatized using expired skimmed powdered milk as a model for simulated pharmaceutical wastewater (SPWW) to improve its performance as a biosorbent. The present study seeks to investigate the potential of using AAS as a biosorbent for removing hazardous Cd ions from industrial wastewater effluents. Up to about 99% of Cd was removed from aqueous solutions of 200 mg L−1 initial concentration using 1 g L−1 AAS and pH 5·5. The corresponding uptake capacity was 197 mg g−1. By comparing the results of AAS to that of non-acclimatized activated sludge, acclimatization proved to be beneficial in enhancing Cd removal by more than ten-fold. Furthermore, biosorption followed a Langmuirian type behavior and the kinetics was best described by the pseudo-second order model. AAS promises to be a cost effective eco-friendly biosorben...

Calculating specific denitrification rates in pre-denitrification by assessing the influence of dissolved oxygen, sludge loading and mixed-liquor recycle

This article presents the results of an experimental study on the correlation among the specific denitrification rate (SDNR), the dissolved oxygen concentration (DO), the F:M ratio (F:M) and the mixed-liquor (ML) recycle in the pre-denitrification reactors fed by domestic sewage. The experimental curves reveal a 28.8–32.0% reduction in the SDNR at 20°C () with DO equal to 0.1 mgO 2 L−1 and F:M in the range 0.2–0.4 kgBOD5 kgMLVSS−1 d−1. The SDNR reduction increases to 50.0–55.9% with DO=0.3 mgO2 L−1. A mathematical correlation of these results and an equation for calculating as function of the F:M as well as the average DO and BOD5 in the total flow rate fed in the denitrification stage are proposed. The conducted experience gives useful suggestions for practical usage, in particular regarding the denitrification reactor design, and represents a good starting point for future applications with the aim to optimize the biological process in domestic sewage treatment plants.

Performance Characteristics of Pollutants along the Longitudinal Profile of a Subsurface Flow Constructed Wetland Domestic Sewage Treatment Plant in the University of Lagos, Nigeria

The paper reports the findings of a research work carried out to examine the performance and efficiency of a subsurface constructed wetland (SSFCW) for the treatment of domestic sewage in the University of Lagos (Unilag), Nigeria. The removal patterns and efficiencies of the physical, chemical and biological sewage pollutants parameters of domestic waste water generated within Unilag community by the SSFCW were studied. The wastewater was sampled and analysed along the SSFCW from influent (point1) to effluent (point 11). Total Dissolved Solids (TDS) reduced from 471 mg/l to 11.85 mg/l (97.48%), Turbidity reduced from 108.75 HTU to 0.05HTU (99.95%), Manganese reduced from 6.05 mg/l to 0.61 mg/ (89.92%), Nitrate reduced from 27.5 mg/l to 2.0 mg/l (92.73%), Sulphate reduced from 48.5 mg/l to 28 mg/l (42.27%), Iron reduced from 1.13 mg/l to 0.03 mg/l (97.35%), BOD reduced from 73.14 mg/l to 12.8 mg/l (82.5%), and E-coli reduced from 874 MPN/100 ml to 0.15 MPN/100 ml (99.98%). On the other hand, Dissolved Oxygen content increased along the SSFCW from 3.14 mg/l to 7.49 mg/l (138.54%) while the pH improved from slightly acid level of 6.49 to slightly above neutral level of 7.05 (9.3%). All the parameters at effluent point are within the Nigerian Federal Environmental Protection Agency (FEPA) acceptable standard. The study concludes that the SSFCW is a cheap, efficient and appropriate technology for the treatment of domestic sewage under tropical conditions.

Source apportionment and quality assessment of surface water using principal component analysis and multiple linear regression statistics

Principal component analysis (PCA) and multiple linear regressions (MLR) analysis were applied on the data set of surface water quality for source identification of pollution and their contribution on the variation of water quality. Results revealed that, most of the water quality parameters were found to be toxic compare to the national standard of Malaysia. PCA identified the sources as, ionic groups of salts, soil erosion and agricultural runoff, organic and nutrient pollutions from domestic wastewater, industrial sewage and wastewater treatment plants. MLR investigated the contribution of every variable with R= 0.968 and R2=0.934 and it was highly significant (p<0.01).

Fate of 1,4-dioxane in the aquatic environment: From sewage to drinking water

Potential health effects of 1,4-dioxane and the limited data on its occurrence in the water cycle command for more research. In the current study, mobility and persistence of 1,4-dioxane in the sewage-, surface-, and drinking water was investigated. The occurrence of 1,4-dioxane was determined in wastewater samples from four domestic sewage treatment plants (STP). The influent and effluent samples were collected during weekly campaigns. The average influent concentrations in all four plants ranged from 262 ± 32 ng L−1 to 834 ± 480 ng L−1, whereas the average effluent concentrations were between 267 ± 35 ng L−1 and 62,260 ± 36,000 ng L−1. No removal of 1,4-dioxane during water treatment was observed. Owing to its strong internal chemical bonding, 1,4-dioxane is considered non-biodegradable under conventional bio-treatment technologies. The source of increased 1,4-dioxane concentrations in the effluents was identified to originate from impurities in the methanol used in the postanoxic denitrification process in one of the STPs. In view of poor biodegradation in STPs, surface water samples were collected to establish an extent of 1,4-dioxane pollution. Spatial and temporal distribution of 1,4-dioxane in the Rivers Main, Rhine, and Oder was examined. Concentrations reaching 2200 ng L−1 in the Oder River, and 860 ng L−1 in both Main and Rhine River were detected. The average monthly load of 1,4-dioxane in the Rhine River was calculated to equal to 172 kg d−1. In all rivers, concentration of 1,4-dioxane increased with distance from the spring and was found to negatively correlate with the discharge of the river. Additionally, bank filtration and drinking water samples from two drinking water facilities were analyzed for the presence of 1,4-dioxane. The raw water contained 650 ng L−1–670 ng L−1 of 1,4-dioxane, whereas the concentration in the drinking water fell only to 600 ng L−1 and 490 ng L−1, respectively. Neither of the purification processes employed was able to reduce the presence of 1,4-dioxane below the precautionary guideline limit of 100 ng L−1 set by the German Federal Environmental Agency.

Investigation of the FeFe-hydrogenase gene diversity combined with phylogenetic microbial community analysis of an anaerobic domestic sewage sludge

Biological hydrogen production through the anaerobic digestion is an environmental friendly alternative for satisfying future hydrogen demands. Microorganisms residing into waste water treatment plants are far from being exhaustively characterized and surveys on hydrogen production through FeFe-hydrogenase in such ecosystems are scarce. This study combined the analysis of 16S rRNA and [FeFe]-hydrogenase (hydA) genes with statistical tools to estimate richness and diversity of the microbial community of a domestic sewage treatment plant at the phylogenetic and functional levels. Archaeal groups were represented by 69 % of sequences assigned to Methanosarcinales and the remaining belonged to Methanomicrobiales. Within the bacterial library, 136 operational taxonomic units (OTUs) were distributed into 9 phyla, being 86 OTUs related to uncultivated bacteria. From these, 25 OTUs represented potential novel taxa within Synergistetes. Proteobacteria was the most predominant (36 % of the OTUs) and diversified phylogenetic group in the bacterial library, most of them assigned to the class Betaproteobacteria. Twenty-two putative hydA sequences were recovered into four distinct clusters and most of them were more closely related to each other than with sequences retrieved from databases, indicating they are hitherto undetected [Fe-Fe]-hydrogenase gene sequences. The richness estimates revealed that the number of sampled sequences was enough for full coverage of the archaeal diversity but not sufficient to cover both bacterial and hydA gene diversities. The results confirmed a great richness and diversity of bacterial and hydA sequences retrieved from the sewage sludge sample, suggesting such environment as a potential reservoir of new hydrogenase genes for biotechnological exploration.