The toxicity of ammonia/ammonium to the vermifiltration wastewater treatment process

A review on integrated vermifiltration as a sustainable treatment method for wastewater

To overcome the scarcity of fresh water, concerned authorities worldwide are bound to think about remediation and reuse of domestic and industrial effluents. The present review study on integrated vermifiltrationwith hydroponic system explains mechanism followed in system and presently the reutilization and remediation of domestic and industrial effluents. It explains the result of integrated vermifiltration and recognizes factors such as clogging, hydraulic loading rate or rain on bed, salinity, and sunlight affect the efficiency of system. The study also focuses on limitations associated with vermifiltration and also suggestions have been made for enhancing the sustainability and performance of existing practices. After literature review, integrated vermifiltration with hydroponic system considered as a natural and eco-friendly method for treating polluted water. Active zone of vermifilter remove organics, nitrate from nitrogen, total and dissolved phosphorus from wastewater. The vermifiltration and integrated vermifiltration with macrophyte able remove chemical oxygen demand (COD) in the range (53.7%-64.4%) and (75.5%-82.8%) respectively. The integrated system reduces land consumption and wastewater can be reutilized in cultivation.

Evaluation of the treatment performance and reuse potential in agriculture of organized industrial zone (OIZ) wastewater through an innovative vermifiltration approach

Vermifiltration (VF) is a natural and sustainable biofilter that has many advantages, including being energy-free, cost-effective, and allowing ease of application and maintenance. In this study, the effectiveness of a lab-scale VF system was assessed by the removal efficiency of total suspended solids, electrical conductivity, chemical oxygen demand, total nitrogen, total phosphorus, fecal coliform, and heavy metals in organized industrial zones (OIZ) and domestic wastewater (DW) for the first time. Additionally, the reuse suitability of the treated wastewater was determined by comparing different countries' and global irrigational criteria. The lab systems were built with four layers: one worm-bed and three varying filtering materials, and operated at an optimum hydraulic loading rate of 1.8-2 m³/m²/day for 45 days with Eisenia fetida as the earthworm species. The results demonstrated that removal efficiencies of total suspended solids and chemical oxygen demand were found to be 95% and 80% in OIZ wastewater and 90% and 88% in DW, respectively. Total nitrogen and total phosphorus were removed at rates of 69% and 67% in OIZ wastewater, respectively, and 84% and 74% in DW. Besides, the VF system has shown satisfactory removal performance for heavy metals ranging from 51% to 77% in OIZ wastewater that has met Turkish national wastewater discharge limits. Although the final characterization of treated wastewater was suitable, heavy metal and fecal coliform levels have not met many countries' irrigation water quality criteria. To meet global irrigation standards and to enhance the VF performance, further experimental studies should be carried out, including parameters such as bed material type in the reactor, worm type, and different operating conditions.

Vermifiltration: Strategies and techniques to enhance the organic and nutrient removal performance from wastewater

The vermifiltration (VF) technology has gained significant attention as a green alternative for remediating domestic and industrial wastewater over the last few decades. Of late, the implementation of various modifications to the orthodox VF technology, including tweaks in the design and operation of the vermifilters, has been portrayed in the available literature. However, owing to the scatteredness of the available information, the knowledge regarding the execution of the modified vermifilters is still inadequate. Hence, an effort has been made to comprehensively overview the innovative strategies and techniques adopted to improve the organic and nutrient removal potential of the VFs from wastewater. In addition, future perspectives have been recognized to design more efficient and sustainable VFs. This review explores more of such novel tactics to improve the performance of the VF technology regarding organic and nutrient removal from wastewater. PRACTITIONER POINTS: Innovative strategies and techniques implemented to VF technology were comprehensively overviewed. Design modification and advantages of each innovation were highlighted. The pollutant removal performance of every modification was emphasized. Modified vermifilters were better than the conventional vermifilters in terms of organic and nutrient removal from the wastewater.

Thermal optimum for mass production of the live feed organism Enchytraeus albidus

Live feed organisms are essential for the larval stages of many fish species grown in aquaculture, and juvenile fish reared on live feeds often exhibit higher survival and growth than those reared on formulated feed. The terrestrial enchytraeid (white worm), Enchytraeus albidus, has potential as a sustainable source of live feed because it can easily be mass produced, feeds on a wide range of organic waste materials and has high contents of protein and long-chain poly-unsaturated fatty acids. In the present study, we observed the effect of temperature on population growth over five months using soil microcosms. At the outset, each microcosm was supplied with approximately the same number of cocoons. Hatched enchytraeids were given rolled oats ad libitum as feed. We followed the population growth at seven temperatures in the range of 4-25 °C and investigated body composition in order to find optimal temperature for mass production. Results showed that E. albidus has a broad thermal optimum range and displays almost similar biomass production in the range of 15-22 °C with specific growth rates between 6.5 and 6.8%. In this temperature range, protein contents were 40-45%, glycogen contents 20-25% and total fatty acid contents 15-20% of dry weight. The temperature had a highly significant effect on fatty acid composition. In particular, the abundance of omega-3 fatty acids (18:3ω3 and 20:5ω3) was largest at low temperature. For what concerns achievable density of worms in mass cultures, our results surpassed previous results and showed that densities close to 100 g L^-1 substrate are realistic. Maximum production of biomass can likely reach 80 g live worms L^-1 month^-1 at temperatures between 15 and 22 °C.

Vermifiltration as a sustainable natural treatment technology for the treatment and reuse of wastewater: A review

With increasing urbanization and industrialization, the scarcity of freshwater is becoming rampant. To counteract this, authorities all over the world are forced to consider the treatment and reuse of the wastewater produced by either industries or domestic units. After an extensive literature survey, vermifiltration coupled with/without macrophyte has been identified as one of the best sustainable, natural and eco-friendly technology for the treatment and reuse of wastewater. Till date, it has been successfully applied for treating domestic wastewater. However, the results from very limited industrial applications are also encouraging and proving its worth for industrial wastewater remediation. The present review on vermifiltration deals with the mechanisms involved and its current status for the remediation and reutilisation of the effluents generated from domestic and industrial premises. The review successfully identifies and explicitly discusses the mechanisms involved in the vermifiltration. The review exhaustively discusses the performance of vermifiltration and identifies the factors contributing to the performance of vermifiltration, which could be of help in designing of the field scale vermifilter based treatment plant. The review identifies the limitations associated with the vermifiltration and suggests possible alternatives, aimed to improve its performance and applicability. The aim of this review is to bring the attention of prospective researchers to study each and every aspect related to the vermifiltration so that it may be adopted as a reliable and dependable technology for the remediation of several industrial effluents meeting the concept of "Zero discharge".

Fate of filter materials and microbial communities during vermifiltration process

The fate of filter materials and microbial communities during the vermifiltration process were studied for 5 months while treating the concentrated greywater. Four filters were filled with 10 cm gravel of which a layer of medium size gravel (5 cm thickness, aggregate size 20-40 mm) at the bottom and a layer of coarse gravel (5 cm thickness, aggregate size 10-20 mm) at the top, then filled with 20 cm sand (d₆₀ = 0.2 mm, d₁₀ = 0.118 mm). Finally, Vermifilter 1 (VF1), control unit and Vermifilter 2 (VF2), were filled with 40 cm fine sawdust (0.05-5 mm) but Vermifilter 3 (VF3), was filled with 40 cm cow dung (0.05-5 mm). Three filters were inoculated with 200 individuals of Eudrilus eugeniae except for the control unit which was filled with sawdust. Five sampling ports were installed on the wall of the filters at 10 cm intervals with reference to the surface of the top layer. Three of the filters were supplied with concentrated greywater and VF1 was supplied with drinking water at the hydraulic loading rate of 16 L m^-2.d^-1 on batch basis, i.e., four times a day at 8:00 a.m., 11:00 a.m., 2:00 p.m. and 5:00 p.m. Weekly, samples from influent and effluent, and monthly, samples of filter materials collected via sampling ports, were collected and analyzed.The removal efficiencies of biological oxygen demand (BOD₅), total chemical oxygen demand (tCOD), and dissolved chemical oxygen demand (dCOD) of VF2 and VF3 were 5-7% higher than the control unit, but little differences were observed in terms of total suspended solids (TSS). However, the removal efficiencies of nutrients for the control unit was slightly better than VF2 and VF3. The pH and Moisture content (MC) of filter materials increased along the depth, but percentage of volatile solids to total solids (VS/TS) decreased through time due to the high number of microbial communities and earthworms dominating the top layer compared to the bottom. The performance of VF2-sawdust was slightly better than VF3-cow dung to treat concentrated greywater.

Determination of the performance of vermicomposting process applied to sewage sludge by monitoring of the compost quality and immune responses in three earthworm species: Eisenia fetida, Eisenia andrei and Dendrobaena veneta

The aim of this study was to assess the effectiveness of vermicomposting process applied on three different sewage sludge (precomposted with grass clippings, sawdust and municipal solid wastes) using three different earthworm species. Selected immune parameters, namely biomarkers of stress and metal body burdens, have been used to biomonitor the vermicomposting process and to assess the impact of contaminants on earthworm's physiology. Biotic and abiotic parameters were also used in order to monitor the process and the quality of the final product. Dendrobaena veneta exhibited much lower resistance in all experimental conditions, as the bodyweight and the total number of circulating immune cells decreased in the most contaminated conditions. All earthworm species accumulated heavy metals as follows Cd>Co>Cu>Zn>Ni>Pb>Cr: Eisenia sp. worms exhibited the highest ability to accumulate several heavy metals. Vermicompost obtained after 45days was acceptable according to agronomic parameters and to compost quality norms in France and Poland.

A mechanistic review on vermifiltration of wastewater: Design, operation and performance

With global population explosion, the available water resources are slowly being polluted due to the excessive human interference. To encounter this, it is the need of this hour to find out sustainable pollution remediating technologies to meet the stringent discharge standards for domestic as well as industrial wastewaters. In addition, those techniques should have the capabilities for effective implementation even in developing countries. Based on the available literatures, one such technique, named vermifilter, has been identified which takes care of almost all the sustainable and economical criteria for its effective implementation even in developing countries. The aim of this meta-analysis is to provide a comprehensive review on assessment mechanisms involved, factors affecting the process and performance of vermifiltration under different scenarios. The present review envisages the current state of the knowledge regarding physical, chemical and biological aspects related to the treatment mechanisms and effective functioning of earthworms. This review has also proposed several suggestive plans on its application at any proposed site.

The use of microbial-earthworm ecofilters for wastewater treatment with special attention to influencing factors in performance: A review

With the unique advantages of lower operational and maintenance cost, the use of microbial-earthworm ecofilters (MEEs) for the wastewater treatment has been increasing rapidly in the recent years. This paper provided an overview of the research activities on the use of MEEs for removing pollutants from various wastewater throughout the world. However, the long-term effective treatment performance and sustainable operation of this system still remain a challenge since the treatment performance would be affected by design parameters, operational conditions, and environmental factors. In order to promote the treatment performance, therefore, this paper also provided and summarized the influencing factors of pollutants removal in MEEs. The design parameters and operational conditions of MEEs include earthworm species and load, filter media type, hydraulic loading rate, nutrient load, packing bed height, chemical factors and temperature. Lastly, this review highlighted the further research on these issues to improve performance and sustainability of MEEs.

Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil

The objectives of soil remediation processes are usually based on threshold levels of soil contaminants. However, during remediation processes, changes in bioavailability and metabolite production can occur, making it necessary to incorporate an ecotoxicity assessment to estimate the risk to ecological receptors. The evolution of contaminants and soil ecotoxicity of artificially phenanthrene-contaminated soil (1000 mg/kg soil) during soil treatment through bioventing was studied in this work. Bioventing was performed in glass columns containing 5.5 kg of phenanthrene-contaminated soil and uncontaminated natural soil over a period of 7 months. Optimum conditions of mineralisation (humidity=60% WHC; C/N/P=100:20:1) were determined in a previous work. The evolution of oxygen consumption, carbon dioxide production, phenanthrene concentration and soil toxicity were studied on sacrificed columns at periods of 0, 3 and 7 months. Toxicity to soil and aquatic organisms was determined using a multispecies system in the soil columns (MS-3). In the optimal bioventing treatability test, we obtained a reduction rate in phenanthrene concentration higher that 93% after 7 months of treatment. The residual toxicity obtained at the end of the treatment was not attributed to the low phenanthrene concentration, but to the ammonia used to restore the optimal C/N ratio.

The risk of sodium toxicity from bed accumulation to key species in the vermifiltration wastewater treatment process

This study was undertaken to assess the toxicological risks from sodium accumulation in a vermifiltration wastewater treatment system to the key worm species, Eisenia fetida. The study found that sodium chloride (NaCl) is the more toxic of the common sodium salts found in wastewater to the worms. The research further found that the worms have an ability to detoxify NaCl although reproduction will be impaired if the worms are exposed to moderate concentrations of NaCl for a long period of time. The actual risk from NaCl toxicity in the vermifiltration process was low however. The low risk was due to the low solid-water partitioning constant of NaCl, which led to a very low predicted environmental concentration (PEC) for NaCl.