Reactor-11: Another unit of reactor, i.e. Reactor-2 was introduced in order to enhance the removal efficiency of the system. In Reactor-11 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. A rectangular plastic container of size (23. 5-inch lengthX 18-inch widthx 15-inch depth) was used to construct the second unit (Reactor-11) of vermin-filtration system. In Reactor-II there were two district layers: firstly, base layer (large pebbles; 10-15 cm in diameter and height about 6-inches), and secondly, top layer (small pebbles; 5-7 cm in diameter mixed with fine sand and height up to 10-inches). The top layer acts as bedding sub-strate for earthworms in Reactor-II. 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. 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. The mean plant density in vermireactor was 0.14 plants/in.-2 (calculated using values of total surface area of Reactor-II and plant numbers in reactors)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. Initially, both reactors were run for two-three days using fresh tap water to wash and fix the layers of vermibeds in proper functioning forms. After establishment of plant stands (after one week) the reactor was run for wastewater treatment experimentations. In both experimental vermi-biofiltration systems, i.e. Reactor-I and Reactor-II individuals of earthworm p. sansibaricus were introduced over the top layer the reactors. 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 initial earthworm density in both vermi-biofiltration systems was measured in the ranges of 22.0-24.5 g/L. The earthworms were allowed to settle in vermireactors for initial 2-3 days and thereafter, vermireactor was run for
experimentation. A reactor without earthworm (bioreactor) acted as experimental control for this study.