Desalination 282 (2011) 95–103Contents lists available at SciVerse ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal Urban wastewater treatment using vermi-biofiltration system Priyanka Tomar, Surindra Suthar ⁎ School of Environment & Natural Resources, Doon University, Dehradun-248001, India a r t i c l e i n f o a b s t r a c t This work illustrates the potential of a novel vermi-biofiltration system in treatment of urban wastewater. A small-scale vermi-biofiltration reactor was constructed using vertical subsurface-flow constructed wetlands (VSFCWs) aided with local earthworms Perionyx sansibaricus. The coco-grass: Cyprus rotundus (density 0.14 plants/in. 2) was used to construct VSFCW. Another reactor without earthworms acted as experimental control. The wastewater was treated through this system for a total of eight repetitive cycles and after each cycle the changes in pH, electrical conductivity (EC), total dissolved solids (TDS), and total suspended solids (TSS), − 3− chemical oxygen demand (COD), NO3 and PO4 of water were measured. Vermi-biofiltration caused signif− 3− icant decrease in level of TSS (88.6%), TDS (99.8%), COD (90%), NO3 (92.7%) and PO4 (98.3%). There were − 3− about 38.8, 20.8, 80.6, 50.8 and 144.6% more removal of TSS, TDS, NO3 , PO4 and COD, respectively in vermi-biofiltration than control. Results thus suggested that vermin-biofiltration system is more efficient than VSFCW in terms of contamination removal efficacy. However, this work provides a preliminary idea of using earthworms in wastewater treatment system and further detailed studies are required on some key issues (e.g., loading rate, flow alternation impacts and earthworm stocking density) of this system. © 2011 Elsevier B.V. All rights reserved. Article history: Received 3 June 2011 Received in revised form 8 September 2011 Accepted 9 September 2011 Available online 13 October 2011 Keywords: Wastewater treatment Perionyx sansibaricus COD TDS Vermi-biofiltration Marshy plants 1. Introduction The urban runoff in general, carries organic load along with several hazardous chemicals which not only spoils the aesthetic sense of the river but at the same time also degrades the aquatic ecosystem. Due to high establishment and running cost of a sewage treatment plant (STP) the majority of urban centers in developing world dispose urban runoff and sewerage water directly into urban river without any treatments or with partial treatments. Several mechanical and chemical approaches are being applied widely for urban wastewater treatments systems in urban centers mainly by sewage treatment plants (STPs). Apart to construction costs the operation and maintenance problems in STPs has raised the question of sustainability [1]. Moreover, excess sewage sludge produced by STPs has been subjected to increasingly stringent limitations on discharge during the last few decades [2]. According to Sinha et al. [3] many developing countries cannot afford the construction of STP and therefore; there is growing concern over developing some ecologically safe and economically viable small-scale wastewater treatment technologies for onsite wastewater treatment. However, at this crucial juncture some ecologically engineered tools can solve issues related with safe and cost-effective wastewater treatments technologies. The majority of present wastewater treatment systems are a “disposal-based liner system” and they should be transformed into cyclical treatments [4] ⁎ Corresponding author. Tel.: + 91 135 2255103. E-mail address:
[email protected] (S. Suthar). 0011-9164/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2011.09.007 in order to conserve the water and nutrient resources. An economical and manageable wastewater treatment approach is often required and deserves to be explored [5]. Biological wastewater treatment process involves the potentials of some living organisms to remove contaminants and sludge from wastewater in order to make it suitable for surface irrigation and other industrial use. Biological wastewater treatment involves the transformation of dissolved and suspended organic contaminants to biomass and evolved gases: CO2, CH4, N2 and SO2 [6]. A variety of organism like aquatic plants, marshland plants, protozoa, nematodes, oligochaetes have been tested in both laboratory and field conditions to develop a low-cost bioreactor for wastewater treatment and sludge reduction. The potential of oligochaetes for wastewater treatment and sludge has been explored widely in many parts of the world. In general, Oligochaetes can be divided into two distinct groups, firstly, microdrilli (aquatic and small sized worms) and, secondly, terrestrial oligochaetes (earthworms) [7]. The aquatic oligochaetes can be divided into two groups: (i) the large aquatic worms (Tubificidae, Lumbriculidae and the semi-aquatic or terrestrial Enchytraeidae) and, (ii) the small aquatic worms such as Naidids and Aeolosomatids [8]. In recent years, both aquatic and terrestrial oligochaetes have been tested by several authors under lab-based trials to remove water contaminants and excess quantity of sludge [3, 6, 8-13]. The major components and outcomes of previous experiments on vermi-biofiltration are described in Table 1. The utilization of earthworms in wastewater or sludge treatment is called vermi-biofiltration. It was first advocated by the Prof. Jose Toha at the University of Chile in 1992 [22]. Vermi-biofiltration is a The microbes play an important role in vermibiofiltration system and they also provide some extracellular enzymes to facilitate the earthworms for rapid degradation of organic substances in vermibeds [25]. inoculated earthworms in vermibeds accumulate many organic pollutants from the surrounding soil environment. [5] Ghatnekar et al. [21] process that adapts traditional vermicomposting system into a passive wastewater treatment process by using potentials of epigeic earthworms. [18] suggested that the vermi-biofiltration system is efficient to remove COD and BOD load of wastewater generated from gelatin industry. Zhao et al. Chiarawatchai [26] has conducted an interesting study on combining vertical sub-surface flow constructed wetlands (VSFCWs) with earthworm. Eudrilus euginae E. rotundus is one of the most invasive weeds and have been reported from tropical and temperate regions of the world. They applied a three-tier biotechnology unit coupled with vermibiofiltration system to convert secondary liquid effluents from a gelatin manufacturing unit into bio-safe clean water. [2] investigated the interactions between microorganism and earthworm in vermi-biofiltration system. total dissolved solids (TDS) by 90–92%. [14] Wei et al. COD (more than 80% removal) and BOD (more than 81%) during the process 20–40% sludge converted into worm biomass and nitrate as well as nitrite removed efficiently References Hendrickx et al. [10] Sinha et al. fetida E. Sinha et al. According to Komarowski [23] in vermi-biofiltration system suspended solids are trapped on top of the vermifilter and processed by the earthworms and fed to the soil microbes immobilized in the vermifilter. agriculture plots. C. Zhao et al. COD by 80–90%. [11] Elissen et al. comprising of earthworm and construction wetland system. fetida Domestic wastewater sludge Secondary liquid effluents from Gelatine Industry Raw sewage Treatment of sewerage and sludge Domestic wastewater treatment E. suggested a significant decrease in COD by 90% and BOD by 89%. Perionyx excavatus. Although.96 P. They demonstrated that earthworm biofilm was dominated by the members of the phylum Proteobacteria and Pseudomonas sp. TDS by 90–92% during the process Significant reduction in pollutant during vermistabilization process Decrease in COD by 90% and BOD by 89%. Limnodrilns Sewage of domestic sludge Lumbriculus variegatus Buys et al. fetida Lumbricus rubellus E. Sinha and his group investigated the potential of vermi-biofiltration system in treatment of dairy industry effluent [3]. TDS by 90–92% from any liquid wastes by the general mechanism of ingestion and biodegradation of organic wastes. Recently. . passive absorption through the body wall and also intestinal uptake during the passage of soil through the gut [24]. Removal of COD by 80–90% and BOD by 90% during vermi-biofiltration Removal of COD by 81–86% and BOD by 90–98% during vermi-biofiltration Removal of COD by 55–66% and BOD by 47–65% during process Hughes et al. The majority of previous studies are available on either utilization of vermi-biofiltration or only constructed wetland filtration system for removal of nutrients/pollutants from wastewaters. According to a study conducted by Ghatnekar et al. Likewise. [19] Xing et al. [15] Song et al. The dissolved and suspended organic and inorganic solids are trapped by adsorption and stabilization through complex biodegradation processes that take place in the “living soil” inhabited by earthworm and the aerobic microbes. Type of sludge/wastewater Worm species used Major observations Sludge reduction was 77% during the process TSS reduced up to 99% after treatment Worm effectively removes major pollutant from sludge There was drastic impact on sludge (46. COD by 80–90%. S. Naidids and Aeolosomatids) Waste sludge produced in wastewater Lumbriculus variegatus treatment plant Waste sludge produced in wastewater Lumbriculus variegatus treatment plant Effluent of activated sludge process Lumbriculida hoffmeisteri Sludge from wastewater water Branchnria Sowerbyi. [2] studied the stabilization of domestic waste water sludge using earthworms and results have revealed that the presence of earthworms in the vermibeds to the significant stabilization of the sludge. rotundus in wastewater treatment and phytoremediation [27–29]. [16] Aquatic worm ((Tubificidae. [3] Wang et al. [17] Earthworms Domestic wastewater (assessment of toxicity of ammonia on earthworm in vermi-biofiltration system) Liquid waste products from dairy industry Eisenia fetida E. The efficacy of vermi-biofiltration system is already described in literature (Table 1). for wastewater treatment. The aim of this study was to assess the potential of an integrated vermi-biofiltration system with VSFCWs constructed by using earthworm Perionyx sansibaricus and a wetland weed Cyprus rotundus (coco-grass or red nut sedge) under a small-scale laboratory experiment. They claimed removal of 5 days' BOD (BOD5) by over 90%. Lumbriculidae.2–66. It is a perennial plant and mainly occurs in gardens. They claimed that earthworms have been found to remove the 5 day BOD by over 98%. [20] Xing et al. [18] Sinha et al. In general. but no comprehensive report is available on utilizing potentials of both systems to develop an effective integrated system. Few earlier studies have demonstrated the capabilities of C. The integration of these two ecological techniques (traditional wetlands system with vermi-biofiltration mechanism) can be a cost effective and sustainable option for onsite wastewater treatment. Intensification of soil processes and aeration by earthworms enable the soil stabilization and filtration system become effective and smaller in size [19]. Suthar / Desalination 282 (2011) 95–103 Table 1 Earlier studies indicating potential of oligochaetes in sludge stabilization and wastewater treatment. Similarly. Results thus. around stagnate water bodies etc. fetida. Tomar. fetida High salt concentration may cause damage to earthworms in vermifltration units Removal of 5 day BOD by 98%.6% in different treatment units aided with earthworms.4% reduction in first stage). and the total suspended solids (TSS) by 90–95% from urban wastewater after the treatment with worms. [19] developed a low-cost sustainable technology over conventional systems to recycle the domestic wastewater with potential for decentralization facility for waste management. COD by 80–90%. The volatile suspended solids (VSS) reduction in the vermibeds was in the ranges of 56. Fine net The fine plastic net (b0. In the top layer of Reactor-I. Reactor-I and Reactor-II individuals of earthworm P. base layer (large pebbles. 1. i. Fresh and viable specimens of plant: Cyprus rotundus were planted in top layer and thin patches of small stones were placed over the open spaces around Cyprus plant to avoid direct hydraulic impact of inflow water in Reactor-II on plant stand and earthworms.2. Other accessories like aeration pump. The top layer acts as bedding substrate for earthworms in Reactor-II. Layer VI Composed of surface vegetation stand of Cyprus. The detail of vermi-biofiltration/biofiltration unit is given in Fig.2. An aeration unit was also fixed in the middle layer of the Reactor-I. It also acts as feed for microbial communities helping in wastewater mineralization. Long unit was constructed with a traditional water filtration system using gravels and sand column at the base and a biofiltration system at the top made of living individuals of wetland plant stand. Following materials/layers were used to fill (from bottom to top) the circular cylinder to construct the vermi-biofiltration/biofiltration unit: Layer I Large stones (10–15 cm in diameter) up to 5-inch — this layer creates a kind of air chamber system and for water storage in base of system. In both experimental vermi-biofiltration systems. A fine plastic net was placed over the pebble layer — aeration device was installed in order to remove BOD load of the wastewater. sansibaricus were introduced over the top layer the reactors.14 plants/in. S.5 mm pore-size) was placed over the leaf litter layer in order to check the entry of earthworm in deep layers of the vermi-biofiltration system — in order to avoid moving earthworm to deep bottom layers of the reactor. In Reactor-II the biological component of the filtration unit was of more importance therefore the majority of the reactor volume was filled with earthworm and plant root zone layers. Dehradun.g. Collected wastewater was brought immediately to laboratory and collected in large-size wastewater reservoir unit of the vermi-biofiltration system. The urban wastewater was collected from a wastewater stream flowing over nearby location of university campus. A plastic circular cylinder of 80 L capacity was used to construct Reactor-I of vermi-biofiltration/biofiltration unit. The thickness of this layer was about 10 in. Reactor-II was introduced in order to enhance the removal efficiency of the system.e. The wastewater was collected from main streamline of wastewater drain in largesize pre-cleaned circular plastic containers of 20 L capacity. A rectangular plastic container of size (23. The roots of plant were planted deeply and surface layer was irrigated regularly (for one week) by tap water in order to fix the planted Cyprus in top layer of vermireactor. Layer II Thick layer of small stones and gravel (5–7 cm diameter) up to 2-inch — acts as filtration unit and creates a kind of turbulence during water flow and provides space for aeration of wastewater. The stock of P. both reactors were run for two–three days using fresh tap water to wash and fix the layers of vermibeds in proper functioning forms. The pieces of stones and pebbles in this root-zone-filtration system create an appropriate space for air and inoculated earthworm in sub-soil system. Wastewater was collected just before the starting of experimentation in order to avoid alternation in the wastewater characteristics mainly due to open storage of sample.P. plant collection and wastewater collection Individuals of earthworm Perionyx sansibaricus of different age group were collected from mud of a gray water drain in university campus. Reactor-II: Another unit of reactor. flow control units. 2. N-fixers.5 g/L. vermireactor was run for .. Nonetheless. 5–7 cm in diameter mixed with fine sand and height up to 10-inches). After establishment of plant stands (after one week) the reactor was run for wastewater treatment experimentations. rotundus was selected for vermi-biofiltration system due its local and perennial availability.0–24. Construction of vermi-biofiltration and biofiltration units The experimental vermi-biofiltration /biofiltration units were comprised of two reactors/batches: (i) long cylindrical unit: Reactor-I and (ii) rectangular unit: Reactor-II. Layer V Vermi-biofiltration bed mainly constructed using thick bedding of soil mixed with small stones and pebbles along with complex root-zone system of surface plant Cyprus rotundus.1. The initial earthworm density in both vermi-biofiltration systems was measured in the ranges of 22. top layer (small pebbles. short length (up to 40 cm) and easy cultivation capabilities. Aeration pipe (pierced 1 inch diameter and 15-inch length). India. ammonifying and denitrification bacteria) responsible for nutrient removal from wastewater. The mean density of Cyprus in vermireactor-I was about19 plants/in. The mean plant density in vermireactor was 0.e. Layer III A thick layer of sawdust spread over the net (2-inch) — saw dust acts as good absorbent for several kinds of inorganic pollutants of wastewater. The identification was made using standard taxonomic key and confirmed by plant taxonomist in university. It was about 4 – 6 in. — earthworm acts as biological agent to remove solid fractions of wastewater and mineralization of wastewater mainly driven by earthworm-microbe interactions in root-zone system. Earthworm. Also provides shelters to beneficial microbial communities responsible for N mineralization. After plantation Cyprus stand was allowed to grow for one week and during this period adequate amount of tap water was supplied in vermireactor to facilitate the fixing of roots of plant in top layers of Reactor-II. In Reactor-II there were two district layers: firstly. 2. A thin plastic net sheet was placed between the both layers to avoid movement of earthworms from top layers to base layer of the vermireactor. Materials and methods 2. sansibaricus was cultured in laboratory using garden soil spiked with leaf litter and cow dung inappropriate ratios. Tomar. were procured from a local sanitary engineering shop and scientific equipment supply firms. Initially. Layer IV Dried leaves of Sal tree were placed over sawdust layer (2-inch) — as natural adsorbent to remove nutrients from wastewater. in length — wetland plant provides air in root-zone system and removes nutrients from wastewater through general absorption. Layer-V the fresh and viable specimens of Cyprus were planted in top soil layers. i.e. The earthworms were allowed to settle in vermireactors for initial 2–3 days and thereafter. the root-zone system not only enhances the efficiency of wastewater filtration but at the same time also provide shelters to bacterial communities (e. Aeration pipe was covered with 1 inch layer of small pebbles. Small passages were made in the surface layers of both reactors in order to facilitate worms to enter in the top soil layers of the vermireactor. The open space between plant stand was filled with a thin layer of small stone to avoid direct hydraulic impact on the plant and earthworm. i. Cyprus rotundus and earthworms in its root zone system. −2 (calculated using values of total surface area of Reactor-II and plant numbers in reactors). i. 10–15 cm in diameter and height about 6-inches). adsorption and translocation processes. water pumps etc. Suthar / Desalination 282 (2011) 95–103 97 C. 5-inch length × 18-inch width × 15-inch depth) was used to construct the second unit (Reactor-II) of vermin-filtration system. and secondly. Plant Cyprus rotundus used for construction of biofiltration unit was originally obtained from moist soils around grey water drains in university campus. In this vermi-biofiltration system efforts were made to create a kind of soil ecological system mainly comprised of thick soil layer spiked with complex rooting system of Cyprus rotundus.e. Observation and data collection The wastewater was used without any dilation for this experimentation.67 863.2 ± 1.00 36. Tomar. After that the outlet of Reactor-I was opened into Reactor-II and Table 2 Characteristics of wastewater used for experimentations.29 216. experimentation.61 ± 0. The care was taken to avoid the overflowing of water.I Aerator Wastewater Tank Outlet from Reactor-I Reactor-I Layer -III Layer -II Layer -I Reactor -II Outlet (completion of cycle Fig.37 ± 0. prior to putting wastewater in experimentation cycle a sample of wastewater (about 1 L) was separated from stock and analyzed for its physic-chemical characteristics (Table 2). The wastewater was filled in reactor continuously up to the saturation level of top layer.0 ± 3.e. S. 1. As illustrated in Fig.V Layer .IV Layer -III Aeration pipe Layer . Vermi-biofiltration system used for wastewater treatment. Parameters pH EC (ΩS/cm) TSS (mg/L) TDS (mg/L) − NO3 (mg/L) 3− PO4 (mg/L) COD (mg/L) Range 7.64 56813.0 ± 5.98 P. i. layer-V.67 ± 7.3 ± 51. However. 2. during experimentation cycle the stock wastewater was supplied in Reactor-I through a mechanical pump and a flow control device was also fixed in main water-supply pipe. The wastewater was sprinkled over the surface of top layer of Reactor-I through a perforated plastic pipe and outlet of Reactor-I was closed to fill the reactor with wastewater. The wastewater was retained for 1 h in Reactor -I and a continuous air was supplied during this period using an electronic aeration device. A reactor without earthworm (bioreactor) acted as experimental control for this study.3.II Layer .3 384. 1. Suthar / Desalination 282 (2011) 95–103 Water Sprinkling Device Supply of wastewater from tank to reactor-I through pump Layer -VI Layer .10 922.60 . 1. 3. there was significant reduction in key pollutants of urban water in both biofiltration (without earthworm) and vermi-biofiltration (with earthworm). Reactor-II.81 in biofiltration (about 9. Statistical analysis A paired sample t-test between control (without earthworm) and experimental (with earthworm) vermi-biofiltration unit was performed for each chemical parameter to analyze the differences..2 7 6. pH The change in pH during different treatment cycle is illustrated in Fig.5. after each treatment cycle. All statements reported in this study are at the p b 0.e. A sample of wastewater was collected in pre-cleaned and sterilized polythene bottle of 1 L capacity from outlet of Reactor-II after each treatment cycle and stored at 4 °C for further investigations on changes in physico-chemical characteristics of wastewater during each cycle. Electrical conductivity (EC) Electrical conductivity (EC) of wastewater showed significant changes after treatment through filtration system in both biofiltration and vermibiofiltration processes. 3. pH of water mainly depends upon a variety of chemical factors. The collected sample of urban wastewater showed relatively high values of some key pollution indicating − 2− parameters of water: TDS (50813 mg/L). mainly by microbes in water. In second cycle of treatment (i. In vermi-biofiltration system EC value of effluent showed increasing pattern up to 5th cycle of treatment thereafter.3 mg/L). Nitrate. organic acids. The pH value of effluent obtained at the end of treatment process was 7. Total dissolved solids (TDS) and total suspended solids (TSS) was measured was measured filtration and gravimetric and oven drying methods. Probably the reduction in the level of ammonia. India). pH was measured using digital pH meter (Metrohm. S.3 mg/L) and COD (863. but difference was more prominent in water from vermi-biofiltration unit than initial levels. 3. ammonia..6 7. 2. sulphate and phosphate contents in water were analysed spectrophometrically by following methods as described by APHA-AWWA-WPFC [30]. dissolved gases. SO4 (293.4 7.05) of effluent from reactors. On the other hand. 2. . The decomposition of organic fractions of wastewater. Although. 7th cycle followed by pH stabilization state during last treatment cycle. The outlet water from Reactor-I was sprinkled over the surface of Reactor-II using a perforated pipe system. The wastewater after vermi-biofiltration process showed a drastic change in its major physico-chemical parameters.7 ΩS/cm in vermi-biofiltration system. Suthar / Desalination 282 (2011) 95–103 99 flow of outlet was controlled using a mechanical flow control device. The increasing EC could be attributed to mineralization of organic waste fractions of wastewater through microbial and 1400 1300 1200 EC Experiment Control ΩS/cm 1100 1000 900 800 700 600 0 1 2 3 4 5 6 7 8 Treatment cycle Fig.8 7. In biofiltration system (control) a trend of slight increment in pH was observed till last observation.0) was used for data analysis.05 levels.2 8 7.2 mg/L). Changes in pH during different cycles of treatment in control and experimental reactor. 3. Chemical analysis The chemical characteristics of wastewater samples collected after each treatment recycle were analyzed for different physic-chemical parameters by following methods as described by APHA-AWWA-WPFC [30]. Tomar. NO3− during biofiltration and vermi-biofiltration treatment caused sight changes in pH. in vermibiofiltration system pH decreased sharply up to 3 rd cycle of treatment thereafter. 3. a trend of gradual increment was observed up to 8. Swiss-made). Conductivity was measured using digital conductivity meter (Remi. SPSS® statistical package (Window Version 13. humic fractions and inorganic salts. 8% more than initial) reactor. 2.P.4. In biofiltration system EC showed a linear trend of increase till last observation while in vermi-biofiltration reactor EC showed different patterns of fluctuation during experimental processes. 21]. Also few earlier researchers have reported increase in pH after vermi-biofiltration processes [19. There was statistically significant difference between biofiltration and vermibiofiltration process for pH level (t-test: p b 0. treatment in Reactor-II) the water retention mechanism and time framework was same as used in Reactor-I. Results and discussion The quality of wastewater in terms of phyico-chemical characteristics is described in Table 2. i. One-way analysis of variance (ANOVA) was also preformed to measure the difference among different cycles for each physic-chemical parameter of wastewater. it reduced sharply till last observation.2. The complete passing of water from both reactors was counted as one treatment cycle and water after each cycle was putted back into new cycle. An interval (stabilization period) of 24 h was kept between two subsequent treatment cycles in order to stabilize the microbial environment and earthworm population in sub-surface of the vermireactor after each cycle. The conductivity of treated water was: 1230.37 mg/L). After that the outlet of Reactor-II was opened to release the water from second reactor. The changes in EC during different cycles are described in Fig.0 Ω S/cm in biofiltration and 984. Chemical oxygen demand (COD) was measured using potassium dichromate oxidation method. The difference between control and experimental reactor was statistically significant (t-test: p =0.1% more than initial) and 8.8 0 1 2 3 pH Experiment Control 4 5 6 7 8 Treatment cycle Fig.e. NO3 and organic acids) which plays an important role in shifting of pH scale of treated water. The different between control and experimental reactor for pH could be related to earthworm mediated rapid mineralization of organic fractions of wastewater. Changes in EC during different cycles of treatment in control and experimental reactor.15 in vermi-biofiltration (about 13. The changes in all reactors could be attributed to the development of biological communities within reactors [26]. The wastewater was repeatedly passed through both units of vermifiltration system for complete 8 cycles. 2.4 8. produces some acidic species of mineralized or− ganic materials (CO2. PO4 2− (36.g. NO3 (384.002). e. 8 ± 2. ammonium and potassium results in increased EC of substrate.7 24.0 186.90 ± 1.0 ± 15. In general. [5] also reported 90. during later filtration in vermi-biofiltration process.0 ± 8. mechanism such as adsorption on ion exchange sites binding to organic matter.001 P = 0.03 t-test c (t-coefficient value) 51. Under another laboratory trial of urban wastewater treatment through vermifiltration. The higher EC of effluent from verminbiofiltration than experimental control was possibly due to high mineralization processes driven by inoculated worm community in reactor [31].67 ± 11. Earlier worker have also reported significant reduction in the COD load during biofiltration and vermibiofiltration processes [3.01 1230.002 P b 0.01 984.0 78.71 − 26. The easy assimilable source of carbon and other available nutrients from earthworm products.4.13 27. by immobilization in sediments via. Results clearly indicated the potential of worms in removal of organic load from wastewater through direct feeding of solid fractions of water or by promoting microbial-mediated organic decomposition process.55 − 374. Recently Xing et al. Wang et al. According to Singleton et al. The level of NO3 in effluent after final treatment cycle was 27. Probably the release of different mineral ions. The presence of earthworm also promotes the microbial colonization in vermibeds and evidences from recent investigation supports this hypothesis [2.7% total removal of NO3 –N in vermi-biofiltration unit that was significantly higher than total removal in biofiltration unit (51. The removal rate was 90% (as compared to initial level) in vermi-biofiltration system and 36.001 Fig. Results thus. when organic waste transits through earthworm gut some fraction of it is then converted into plant available forms [25]. the geological and microbial system in control biofiltration unit is responsible for COD reduction while in vermi-biofiltration system enzymes.8% in biofiltartion system.001 P b 0.2% average removal efficiencies of vermi-biofiltration system for COD of a domestic wastewater.04 86.3 ± 5.100 P.03 545. Paired sample t-test between control and experiment. Zhao et al. The COD removal rate was 84% in vermi-biofiltration system after completion of 8 cycles of treatment. might be responsible for reduction in EC.82 91. Changes in COD during different cycles of treatment in control and experimental reactor.02 12. casts and mucus accelerates the microbial colonization in earthworm-containing vermibeds. Reactor with earthworms (biofiltration). [18] have investigated the impact of vermi-biofiltration system on chemical characteristics of wastewater generated from gelatin industry.001 P b 0. after 5–6 cycles of treatment EC of effluent water from vermi-biofiltration reactor showed sharp decrement till last observation.92 ± 2.81 ± 0.e.9 mg/L − for biofiltration unit. incorporation into lattice structure and precipitates into insoluble compounds [37].113 − 69. COD COD is an important indicator of organic load of urban wastewater.67 ± 0.9 mg/L for vermi-biofiltration unit and 186. Suthar / Desalination 282 (2011) 95–103 earthworm activities in reactors. 34]. such as phosphate.15 ± 0. Also Ghatnekar et al. [35] earthworm hosts millions of decomposer microbes in their gut and excreate them in soil along with nutrients in worm casts.001). They claimed about 90% reduction in level of COD at the end of process.67 ± 2.93 0. The changed in COD load of wastewater during different treatment cycles is illustrated in Fig. [2] investigated the earthworm-microorganism interaction during wastewater sludge treatments and results suggested about 46% reduction in the contents of volatile suspended solids due to earthworm-microbial action after treatment process. Chiarawatchai and Nuengjamnong [36] and Chiarawatchai [26] suggested that earthworms contributed to the wastewater remediation during the treatment process within the VSFCWs. However. In this study there was significant impact on nitrate concentration − in effluents after treatment in both experimental reactors.40 ± 1. b c Reactor without earthworms (vermi-biofiltration). In control biofiltration system COD reduced gradually during treatment cycles while in vermi-biofiltration system COD level of effluent water reduced rapidly after 1st treatment cycle (Fig. [3] studied the vermifiltration of wastewater originated from dairy industry under a pilot-scale project.6 ± 5. reduce the those chemicals which otherwise cannot be decomposed by microbes [19. Such nutrients further enhance the microbial quality and quality of the vermibeds.001). 21].62 ± 0.001 P b 0.. 4. The microbial association with worms in vermifiltration system could be important for removal of organic load form wastewater. but vermi-biofiltration showed more removal efficiency than biofiltration reactor (t-test: p b 0. Moreover the formation of biofilms of decomposer microbes in the geological system of the vermireactor also promotes COD reduction during vermifiltration process [3]. secreted by earthworm and gut-associated microflora. Tomar.86 − 160. accumulation of salts by inoculated worms. Parameters pH EC (ΩS/cm) TSS (mg/l) TDS (mg/l) − NO3 (mg/l) 3− PO4 (mg/l) COD (mg/l) a Control reactor a 7. 32] and were moderately higher than those detected in horizontal flow constructed wetlands planted Table 3 Chemical characteristics of outlet from biofiltration (control reactor) and vermi-biofiltration (experimental) at the end of process. There was about 92. NO3 –N Nitrate is an important indicator of water pollution and its high concentration in freshwater bodies leads to eutrophication problem. This could be because earthworms and aerobic microbes act symbiotically to accelerate and enhance the decomposition of organic matter [33].50 − 22. 25]. 4.001 P b 0. They claimed the average COD reduction in the ranges of 80–90% at the end.3% removal) (t-test: p b 0. But NO3 reduction arte was prominent in vermi-biofiltration unit than biofil− tration system (Table 3). The results of removal efficacy of biofiltration system were similar to those observed in constructed wetlands by other researchers [28.93 Significance level P b 0.00 9875. In general. S.86 − 1179. i. Moreover. Sinha et al. Sinha and his associates reported about 45% reduction in COD load after treatment [19] and removal rate was significantly high in experimental reactor than control one (without worms). clearly indicate that vermi-biofiltration may be an efficient treatment tool for designing of a low-cost domestic wastewater treatment facility. This could be due to adsorption and/or absorption of inorganic constituents of water by different biological or non-biological components [32] of vermi-biofiltration system. The EC reflects the salinity of any material and it is a good indicator of the mineralize fraction of wastewater. The COD load in effluents from biofiltration and vermi-biofiltration system was significantly low than initial levels. 3. − 3. [21] have reported significant COD reduction (47 – 58% than initial) during vermi-biofiltration of domestic wastewater. . In traditional wetland biofiltration system the nutrients and metals may be removed from the polluted water and retained in the sediment and taken up by the plants and by microorganisms associated on the surface of the roots and sediments.3. 4).0 Experimental reactor b 8. 3% and that was significantly higher than removal efficiency of biofiltration 3− system (65. i.63 to 14. The patterns of PO4 removal during different treatment cycles is described in Fig. Phosphate (PO4 ) in wastewater is household drains and urban runoff water containing excreta and other organic substances [21].0 to 62. Suthar / Desalination 282 (2011) 95–103 101 with Phragmites by Vymazal [38] and with Canna and Heliconia by − Konnerup et al.). addition of aeration device in current biofiltration system was an advantage over traditional biofiltration or wetland filtration systems. TSS and TDS As described in Table 3. better results of this study than previous report could be attributed to substrate quality. He suggested some technical improvements like replacement of substrates from gravel or sand to ones with high phosphorus adsorption capacities to enhance phosphorous removal capability of vermi-biofiltration unit. nitrous oxide (N2O) and finally to molecular nitrogen − (N2) [40]. Tomar. results of phosphorus removal contrasts with finding of Chiarawatchai [26] who reported least impact of earthworm inoculation on phosphorous removal from wastewater during vermi-biofiltration process. . In general.5.3% NH4–N removal in wastewater after treating through vermi-biofiltration system. 6.001). Xing et al. Preetha and Kumar [43] demonstrated more 3− than 99% removal of PO4 from wastewater using sand-column treatments device.62 mg/L) than sample collected from final stage of biofiltration system (12. The high NO3 –N removal efficiency of current biofiltration system than previous reports could be explained in terms of oxygen supply in rhizosphere of biofiltration system.6. the level of PO4 in final effluent from biofiltration system was comparatively high than prescribed limit. oxygen is released by roots of plants in constructed wetlands and it should be sufficient to meet the demand for the aerobic bacterial − communities which are mainly responsible for NO3 –N removal from wastewater. The level of PO4 in treated effluent from biofiltration and vermibiofiltration is of prime concern because high concentration of such substance is responsible for eutrophication in surface freshwater re3− sources. followed by further reduction to nitric oxide (NO). activities of earthworm and associated microflora in vermibeds also promote rapid P-mineralization in the sys3− tem. [5] reported efficient removal of + NH4 –N (with 85. 42]. The ligand exchange reactions and physical adsorption or sorption sites rapidly removes phosphorous from the soil solution. [21] reported about 7. Vymazal [38] also pointed out that in most system designed for the treatment of domestic or municipal sewage the supply of dissolved organic matter is sufficient and aerobic degradation is limited by oxygen availability. However. 3− The PO4 removal efficiency of current biofiltration system with Cyprus stand was relatively higher than those detected in horizontal flow constructed wetlands planted with Phragmites by Vymazal [38]. Although. The source of phosphate Total suspended solids (TSS) and total dissolved solids (TDS) showed drastic reduction during biofiltration and vermi-biofiltration − Fig. Moreover.2%) (t-test: pb 0. There was rapid removal in vermi-biofiltration unit than the biofiltration unit in the first and second cycle of the treatments and that could be due to filtration of suspended substances during first cycle of treatment which are considered to be feed materials for earthworms in vermi-biofiltration system. [39]. calcium carbonate and layer silicate minerals are important sites for sorption of phosphate anions [41. The different between biofiltration system and vermifiltration system for removal rate should be explained in terms of the population and activities of nitrogen metabolizing bacteria. The supply of oxygen also promotes the activities of heterotrophic and ammonifying bacteria which are mainly responsible for nitrate removal from wastewater. there was significant different between 3− inlet and outlet water for PO4 concentration in both treatment reactors. The trend of changing NO3 -N level during the treatment cycles is described in Fig. The presence of earthworm in rhizosphere sub-system has some advantages over traditional biofiltration system because of the direct impact of earthworms on aerobic heterotrophic bacterial communities which are mainly responsible for N-mineralization in − wastewater biofiltration systems. Therefore.0 mg/L as decided by national pollution monitoring agency. In soil column the hydroxides and oxides of Al and Fe.e. removal rates declined sharply. 3− Fig. plant type etc. 5. In general. The final effluent from vermi3− biofiltration system showed low concentration of PO4 (0. Moreover. 3− 3. According to Bostrom et al. denitrification processes involved the initial NO3–N reduction to NO2–N.1% of removal rate) while studying wastewater treatment using an earthworm-based ecological filter integrated constructed rapid infiltration (Eco-CRI) system. earthworm-mediated rapid nitrogen transformation − leads to rapid NO3 -N loss from wastewater. Wang et al. It is clear that in biofiltra3− tion system the removal trend for PO4 is slow and linear but in vermi3− biofiltration reactor there was a trend of sharp PO4 removal up to 5–6 cycles of treatments thereafter. Central Pollution Control Board (CPCB) for surface discharges of treated water. However. biofiltration and vermi-biofiltration.9% total N and 21. However. 3.e. 5. Probably the sand mixed column of current biofiltration reactor was advantage over the previous biofiltration systems. In current vermifltration system the top layer composed of sandy soils along with mixtures of large stones and pebbles. it is sug3− gested that high PO4 removal could be due to addition of aeration device in our vermi-biofiltration system. i. 3− The PO4 removal efficiency of vermi-biofiltration was recorded 98. 6. [44] aerobic conditions are more favourable for P sorption and co-precipitation therefore. Changes in NO3 during different cycles of treatment in control and experimental reactor. 5. i.7–97. Changes in PO4 during different cycles of treatment in control and experimental reactor.P.67 mg/L).e. NO3 –N reduction rate was relatively high in this study than previous reports and probably that attributed to oxygen supply in the system. design and biological components (earthworm species. Chiarawatchai [26] reported significant reduction in level of nitrate in effluents obtained from a labscale microcosm wastewater treatment unit than effluent from reactor without worms. S. But in this study the integration of these two components (traditional constructed wetlands system and earthworms has been applied to design a cost effective and sustainable option for onsite wastewater treatment. Fig. Water Res. N.7% after treatment process. Michigan Technological University. P. Changes in TDS during different cycles of treatment in control and experimental reactor. They have attributed the TSS removal to continuous consumption by earthworms. i. [3] reported total removal of TSS and TDS in the ranges of 90–92% and 90–95%. References [1] S. earthworm-microbial interaction etc. Rose. CFP Report Series: Report 27. respectively). Volkman. Xing.001) (Table 3). Conclusions This work provides an opportunity to explore the efficiency of a vermi-biofiltration system (mainly constructed by using a wetland weed Cyprus rotundus and live biomass of a local earthworm P. 1999. Tomar. Changes in TSS during different cycles of treatment in control and experimental reactor. M.e. Indian J. microbial ecology in vermibeds.K. Earthworm–microorganism interactions: A strategy to stabilize domestic wastewater sludge. J.D. The removal pattern of TDS in both filtration systems is described in Fig. Bharambe.e. Glyceria maxima. The efficacy of vermi-biofiltration system in TDS and TSS removal is also reported by earlier authors. Acknowledgement We would like to thank four anonymous reviewers for critical comments and fruitful suggestions on earlier version of the manuscript. Removal of high BOD and COD loadings of primary liquid waste products from dairy industry by vermifiltration technology using earthworms. process (Fig. Ganesh Bahuguna. Li Xi. G. Zhao. [4] G. Carex riparia. However. Zheng. They have reported significant removal of TSS. According to a study conducted by Prabu and Udayasoorian [28] Phragmitis australis. Li. . [2] L.001). D. According to Cooper et al. 82. i. The control (biofiltration) system showed a gradual removal of TDS during different cycles of treatments process while in vermi-biofiltartion system TDS removed sharply during initial 3–4 cycles thereafter. Sinha. Community-Based Technologies for Domestic Wastewater Treatment and Reuse: Options for Urban Agriculture. D. Fig. [3] R. Deng. 9). results clearly indicates the efficacy of vermibiofiltration system in wastewater treatment but further detailed studies are still required to answer few key issues of this system. respectively TSS from wastewater after treatments.g. The removal rate was high in vermi-biofiltration unit (88.8%) (t-test: p b 0. [45] and Vymazal et al. Eng. 36 (2010) 827–883.6% (t-test: p b 0. Yang. 7. Y. Division of Pollution Prevention and Environmental Assistance. Suthar / Desalination 282 (2011) 95–103 Fig. Yang. Environ. Y.102 P. Master's Thesis (2003). 27 (6) (2007) 486–501. Xing et al. Kamal and Digpal Negi) during experimentation is also acknowledged here. more detailed is needed to establish the relationship between removal of solids and earthworm working mechanism in vermi-biofiltration system. According to this study earthworm presence in treatment system caused about 57 to 79% reduction in total content of suspended solids in wastewater. Mustafa et al. 4. Namita Tiwari. Ecol. Results thus clearly suggested the capability of earthworms to remove solid fractions of wastewater during vermi-biofiltration processes. Philarius arundiraecae and Juncus effuses in wastewater treatments. 7 and 8.6% than initial level) than biofiltration system (63. Wang. Sinha et al. Results clearly suggested that integrated vermi-biofiltration reactor was more efficient than traditional biofiltration system in terms of removal of key chemical pollutant from wastewater (Fig. Protec. Zhang.8% in vermi-biofiltration unit and that was significantly higher than total removal in biofiltration system. 93. Ding. Although. [21] demonstrated the results of a small-scale vermifiltration unit for domestic wastewater treatment. Bapat. Q. [46] the suspended solids that are not removed in pre-treatment system are effectively removed by filtration and settlement processes. Similarly TSS also reduced significantly in wastewater obtained from both experimental reactors (biofiltration and vermibiofiltration) at the end of process. [5] D. sansibaricus) in treatment of urban wastewater. 44 (2010) 2572–2582. Sustainable wastewater treatment and reuse in urban areas of the developing world. Changes in different parameters of wastewater during different cycles of treatment in control and experimental reactor. [47] reported the potential of integrated constructed wetland system with Typha latifolia.C. hydrolic load. The kind cooperation of laboratory staffs (Mr. 7. A full-scale treatment of freeway toll-gate domestic sewage using ecology filter integrated constructed rapid infiltration. Cyperus pangorei and Typha latifolia planted biofiltration system removed about 77. W. respectively. The difference between both systems could be due to difference in biological components and working capabilities of both reactors. The total reduction in TDS content was about 99. X. 72 and 67%. Earlier scientific approaches were based upon the use of either plant or earthworm in biofiltration unit design. S. Wang. 8. 9. e. The results of present study corroborates with the findings of other scientists who claimed importance of earthworm in vermifiltration system. Yi. retention time impact. the removal process was more or less steady till last observation. Zi. Mater. Technol. Leiden.S. [19] R. Pilot-scale vermireactors for sewage sludge stabilization and metal remediation process: Comparison with small-scale vermireactors. Cocomposting with and without Eisenia fetida for conversion of toxic paper mill sludge to a soil conditioner. .. pp.D.S. Kumar. J.F. Hendrix. Soil Pollut.H. Ecol. subsurface flow constructed wetlands planted with Canna and Heliconia. Sinha. Buisman. J. Job.P. Elissen. 17–66. D. P. Fan. O. Wei.H. M. Publication of Australian water and waste water association. Konnerup.C. C. Borger. [21] M. [13] T. R. Eng. Sludge reduction with Tubificidae and the impact on the performance of the wastewater treatment process. Wetland treatment (HSSP) of wastewater from a milk-processing unit using Bambusa vulgaris. Elissen. R. Delwiche. Earthworms in Waste and Environmental Management. Soil Sci.W. M. 40 (2006) 3713–3718. Chiarawatchai. Water Res. African J. E. D. Technol. Loehr. Edwards. Ghatnekar. Phosphorus release from lake sediments. [9] Y. APHA-AWWA-WPCF.S.C. The Netherlands. Calheiros. Biochem.P. Dominguez. Li.S.T. 1996. Academic Pub. J. [18] S. J.L. Yang. Ecol. Lumbricidae) modifies the structure and physiological capabilities of microbial communities improving carbon mineralization during vermicomposting of pig manure.P. S. Implementation of earthworm-assisted constructed wetlands to treat wastewater and possibility of using alternative plants in constructed 103 [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] wetlands. Kien. Med. Application of vermi-filter-based effluent treatment plant (pilot-scale) for biomanagement of liquid effluents from the Gelatine Industry.. 105 (2010). Water Res. Klapwijk. J. Perfler. Anh. 9 (44) (2010) 7513–7520. [11] T. Anh. Marlow. Hamburg University of Technology. Environ. H. Y. Treatment performance of small-scale vermifilter for domestic wastewater and its relationship to earthworm growth. R. Hydrobiol. Tomar. J. Liang. Temmink.P. Medmenham. Aquatic worms eating waste sludge in a continuous system. Inarkar. Sci. Li. Buys. [14] J. Eisenia fetida (Oligochaeta. Brix. Biochem. [25] S. Phosphate movement in column of sandy soil from a waste water treated site.J. [23] S. Carroll.15–19 May 2005 . Ergebn. Rulkens. Harrington.V. [15] Y.N.R. J Environ Sci Eng. C. Shutes. Suthar / Desalination 282 (2011) 95–103 [6] Y. Buisman.G. Morand. [10] R. Temmink.K. 2001.. Treatment of domestic wastewater in tropical. R. Haberal. Doctoral Thesis. Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis. Ho. P. M. Xing. T.. Biotech. Thai J.L. Haz. [8] M. The risk of sodium toxicity from bed accumulation to key species in the vermifiltration wastewater treatment process. R.J. Backhuys Publishers. pp. S.C. J. F. London. Dynamic Plant (2010) 83–88.K. Environ. The effect of operating conditions on aquatic worms eating waste sludge.A. American Public Health Association. U. Long-term performance of a representative integrated constructed wetland treating farmyard runoff. S. 30 (1976) 241–262. Elissen.K. J. Vet. Ecol. Xing. 35 (2009) 248–257. G. P. Aira. UK. Microorganism-Earthworm-Integrated-Biological-TreatmentA sewage Treatment for Rural Settlements .P.C. Reed Beds and Constructed Wetlands for Wastewater Treatment. Yang. Bryan. Coleman. F.D. S. T.N. Wat. C. Xing. Manselli. Stephenson. Bharambe. Suthar. 43 (2009) 239–245. [16] X. 32 (4) (2008) 301–309. Mckenna. 99 (2008) 8360–8366.J. Mn and S chemistry of sphagnum peat in four peat lands with different metal and sulphur input. Tech. H. Nair. C. Electr. Sharma. Taylor and Francis.F. Castro. Stabilization of liquid municipal sludge using earthworms.Germany and Poland. Horizontal sub-surface flow and hybrid constructed wetlands systems for waste water treatment. Water Res. Dynamic Soil. Li. J. Liu. Laplanche. J. Technol. S. Rup. Nuengjamnong. Purification of wastewater by vermifiltration. L. Microbial Ecol. W. [26] N. Microbiol. Vymazal.G. Tan. Removal mechanisms and types of constructed wetlands. Bioresour. A. A. M. [12] T. Environmentalist 28 (2008) 409–420.H. Hughes. Y. J.T. H. D. Komarowski. Singh. Cluzeau. 1988. Eng.S. Denitrification. Bouche. R.Frankfurt (Oder) and Slubice . Eikelboom. Weider.G. J. Vermifiltration as a stage in reuse of swine wastewater: monitoring methodology on an experimental farm. July. 163 (2009) 199–206. 101 (2010) 8192–8198. Ghatnekar. Bioresour. The Hague. Hendrickx. J.G. Zhu. Bioresour. [17] R. 100 (2009) 3205–3213. 185 (2011) 881–888. Aquatic worms eat sludge: mass balances and processing of worm faeces.D. 140 (1985) 59–68. Food Chem.B. Aguilera. J. Phytoremediation potential of indigenous plants from Thai Nguyen province. G. Laber. in: C. 54 (2007) 662–671. Ph. Nutrients release and phosphorus distribution during oligochaetes predation on activated sludge. Neuhauser (Eds. Lin. Buisman. Dhaliwal. R. Prabu.. Houten. S. Xin. J. 7 (13) (2008) 2661–2666. J. M. 11 (415) (1979) 215–225. Song.H. J. Kim. A. Bioresour. Qui. Identification of uncultured bacteria tightly associated with the intestine of the earthworm Lumbricus rubellus (Lumbricidae. Chaudhari. Temmink. Effect of redox potential and pH on phosphate removal from waste water during land aaplication. 43 (2009) 943–950. Technol.M. Eng. Environ. 18 (1982) 5–59.J. Eng. 1923.). N. Minimization of excess sludge production for biological wastewater treatment.L. Buisman. Mustafa. Limnol. Hendrickx. WRc Publications.J.H. L. E. 35 (2009) 779–790. Agricul. reproduction and enzymatic activity. M. Technol. Vermistabilisation of municipal sewage sludge amended with sugarcane trash using epigeic Eisenia Fetida (Oligochaeta). Bostrom. Z. J. EJEAFChe 6 (1) (2007) 1689–1701.J. Tandon. pp. T. Y. Wei. Ecol. Monroy. Lu.T. M. Udayasoorian. Mater. C. G. Singleton. R. A new reactor concept for sludge reduction using aquatic worms. Kavian.L. N. [7] J. J. T.. Eng. M. Lee. 25 (2005) 478–490. [20] M.H. S. 39–43. Haz.B. A. Eng. Wat. Hassouna. 15th ed.N. Hazard. Cooper.U. H. H. Callarec. Wang.T. X.H. M. Rev.E. Li. SPB. Typha latifolia and Cyperus rotundus. 95–110. C. Arch. J. P. J. C. Hall. Kumar. [24] S. Patrick.C. P. Kaur.F.C. H. Rangel..L. Hendrickx. 21073 Hamburg. J. P.J. Brix. J.. Soil Biol. B. 100 (2009) 4642–4648. 19 (2007) 257–263. Development of a test method to assess the sludge reduction potential of aquatic organisms in activated sludge. G. Hendrickx. Proc. Annu. C. Fe. W. D.E. 35 (2003) 1547–1555. P. J. Germany.T. Flaig. Y. Cooper. G. The use of earthworms in lab-scale constructed wetlands to treat swine wastewater.H. P. Jansson. R. Lang.C.J.G. Whitman. Mat. ICID 21st European Regional Conference 2005 . C. Standard methods for the Examination of Water and Wastewater.C.N. A. [22] M. D. 177 (2010) 633–638. Holford Jr. R. 1998. Yu. Water. 37 (2003) 4453–4467. Hu. Vietnam. Vermiculture for sewage and water treatment sludges. Y. 100 (2009) 3815–3819.S. Air.C. 1994. Biol. Chiarawatchai.P. Suthar. Forsberg. Preetha. F. 39 (2) (2009) 157–162.S. Sewage treatment by vermifiltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization.D. D. Tua. p.R. D. Fauna of British India (Oligochaeta). 36 (2010) 703–712. Koottatep. Vig.B. Zhang. van. Y.L. A. H. 29 (1986) 309–320. H. Rhizosphere treatment technology for community wastewater treatment. 188 (2003). Beih. Treatment of pulp and paper mill effluent using constructed wetland. University of Montpellier 2. Song.C. Oligochaeta). D.B.D. H. Scholz. Washington. Yang. Al. Ghatnekar. Wang. A comparative study of synchronous treatment of sewage and sludge by two vermifiltrations using an epigeic earthworm Eisenia fetida. Dappelo. H. B. Green.A.J.B. 52 (2010) 23–26. Vymazal. Bioresour. C. Ecol. B. M. Temmink. Thesis. Elissen.S. 32 (2011) 257–262.