Toxicity of domestic wastewater pH to key species within an innovative decentralised vermifiltration system

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.

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.

Nitrogen removal in vermifiltration: Mechanisms, influencing factors, and future research needs

To meet global health and sanitation goals, there is a continued need for sustainable wastewater treatment alternatives that require minimal energy and investment. Vermifiltration, a technology gaining relevance in Africa and Asia, may be an alternative to traditional wastewater treatment systems due to its cost-effectiveness, ease of application and maintenance, and sustainability. However, nitrogen removal in vermifiltration is not well understood since most of the prior research focuses on organics removal. Thus, a state of the art review is necessary to separately focus on the mechanisms associated with nitrogen removal in vermifiltration, along with the factors affecting nitrogen removal. For the first time, this review attempts to present the types of vermifilter based on their flow pattern. The review further discusses the current status of the application of vermifiltration, along with the benefits and limitations associated with the adoption of this technology. It also explores possible strategies that could be adopted to maximize the nitrogen removal potential of vermifilters as optimizing nitrogen removal is critical for improving the performance of vermifiltration based treatment systems.

Understanding intricacies of clogging and its alleviation by introducing earthworms in soil biofilters

With the scarcity of fresh water and rise in pollution load in the aquatic ecosystem over the globe, the domestic and industrial effluents need to be reused after suitable treatment. In an attempt to do so, soil biofilters have been identified as a treatment alternative that is suitable for application in developing countries. However, rapid development of clogging in the soil biofilters limits its applicability as an effective technology. This paper aims to understand the occurrence of clogging due to biofilms formation in and over the bedding of soil media. To address this, the organic loading rates (OLRs) were varied in the range of 2.25-11.25kgCOD/m³·day to create different degree of clogging. Earthworms were inoculated into the soil bedding at the earthworm densities (EWDs) of 0, 5000 and 10,000earthworms/m³ to study the effect of earthworms introduction on clogging. The degree of clogging was measured using clogging coefficient (CC), hydraulic conductivity and head loss. The study highlights the impact of earthworms on the removal performance and clogging of soil biofilter. For all earthworm densities, head loss and clogging coefficient increased and hydraulic conductivity decreased linearly with organic loading rate. Introduction of earthworms versus no earthworms resulted in lower head loss and clogging coefficient and higher hydraulic conductivity for all organic loading rates, while increasing EWD from 5000 to 10,000 had only marginal effects on all parameters. The study reveals that high organic loading rate activates higher number of microbial sites, in turn causing higher degree of clogging. However, the introduction of earthworms reduces the clogging rate significantly along with enhanced treatment performance. The outcome of this study indicates that incorporation of earthworms into the soil biofilter can reduce the degree of bio-clogging and might provide a highly sustainable, low cost and efficient treatment system for the developing countries.

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.

Substrate removal kinetics and performance assessment of a vermifilter bioreactor under organic shock load conditions

In the present study, the effect of short-term organic shock loads (675, 799, 1,084 and 1,410 mg COD/L) on the treatment performance of a pilot-scale vermifilter (VF), employing an epigeic earthworm Eisenia fetida and treating synthetic domestic wastewater is investigated. The effect of organic shock loads on the performance and stability of vermifiltration reactor was evaluated to identify its feasibility in actual field conditions. Prior to the application of each organic shock load, normal loading conditions were maintained to achieve the pseudo steady state (PSS) conditions. The results showed satisfactory endurance against imposed organic shock loads with negligible reduction in chemical oxygen demand (COD) removals and it was almost similar to PSS condition with removal efficiencies of ∼ 66, 71, 67 and 68%, respectively. The experimental COD data fit well to first-order kinetic model, with a regression value of 0.95. At the end of all shock loads, the nutritional analysis of vermicompost obtained from the top layer of VF, showed increased concentration of total nitrogen (∼31 g/Kg) and total phosphorus (29 g/Kg). Besides, an augmented earthworm biomass, ∼23.2% on weight basis and ∼22% on number basis, was observed at the end of the study.

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.