Constructed wetland applications have been limited by a large land requirement and capital investment. This study aimed to improve a shallow pond water hyacinth system by incorporating the advantages of engineered attached microbial growth technique (termed Bio-hedge) for on-site domestic wastewater treatment. A laboratory scale continuous-flow system consists of the mesh type matrix providing an additional biofilm surface area of 54 m 2 /m 3 . Following one year of experimentation, the process showed more stability and enhanced performance in removing organic matter and nutrients, compared to traditional water hyacinth (by lowering 33%-67% HRT) and facultative (by lowering 92%-96% HRT) ponds. The wastewater exposed plants revealed a relative growth rate of 1.15% per day, and no anatomical deformities were observed. Plant nutrient level averaged 27 ± 1.7 and 44 ± 2.3 mg N/g dry weight, and 5 ± 1.4 & 9±1.2 mg P/g dry weight in roots and shoots, respectively. Microorganisms immobilized on Bio-hedge media (4.06 × 10 7 cfu/cm 2 ) and plant roots (3.12 × 10 4 cfu/cm) were isolated and identified (a total of 23 strains). The capital cost was pre-estimated for 1 m 3 /d wastewater at 78 US$/m 3 inflow and 465 US$/kg BOD5 removed. This process is a suitable ecotechnology due to improved biofilm formation, reduced footprint, energy savings, and increased quality effluent. OPEN ACCESSWater 2015, 7 330

The use of aquatic macrophytes for the domestic wastewater treatment is increasing in various parts of the world. The aim of this study is to examine the potential of shallow pond system using water hyacinth (Echhornia crassipes) along with the microorganisms present in the bio-film attached to the roots and water column for treatment of domestic wastewater in the presence of high total dissolved solids (TDS) and heavy metal salts. The shallow pond system is different from conventional water hyacinth system and it has high oxygen rich zone to provide the superior growth of aerobic microorganism. The studies indicate that, water hyacinth can tolerate TDS up to 2000 mg/L in the shallow pond system. The heavy metal removal is a function of phytoaccumulation or phytoextraction, which can lead to morphological deformity if heavy metals exceed the saturation limit of 268 & 2152 mg/kg Cd, 381 & 3372 mg/kg Cu, 229 & 1850 mg/kg Ni, 462 & 2764 mg/kg Zn, in shoots and roots respectively. The reduction in TDS is marginal (19%) at the highest tolerable limit whereas the heavy metal reduction is 66 %, 68 %, 64 %, 70 % for Cd, Cu, Ni and Zn respectively at the outlet of the treatment system. The sewage treatment performance of the shallow pond water hyacinth system for all other parameters is estimated as 81 % Chemical oxygen demand (COD), 91 % Biochemical oxygen demand (BOD 5 ), 16 % Total dissolved solids (TDS), 70 % Total suspended solids (TSS), 4 % Chlorides, 74 % Ammonia nitrogen (NH 3 -N), 41 % Phosphate (PO 4 -P), 96 % Most probable number (MPN) and 98 % Total viable count (TVC) reduction.

The applications of biofilm treatment technologies for domestic wastewater are being increased in many parts of the world. The aim of the study is to assess a compacted aerobic attached growth fix-film unit (termed Bio-cache) for treatment of small volume domestic wastewater. The system consists of the miniature plastic packing matrix, which provides a large surface area of 300 m 2 /m 3 , so as to maintain the high rate growth of viable organisms responsible for organic degradation. The study on the Biocache was undertaken in a laboratory scale and analytical data were collected before and after treatment. This paper also investigates microbial flora present in the system by isolating and identifying the microorganisms. At the optimum hydraulic retention time (HRT) of 2 h, approximately 78% Chemical Oxygen Demand (COD), 88% Biological Oxygen Demand (BOD 5 ), 32% Total Dissolved Solids (TDS), 72% Total Suspended Solids (TSS), 9% Chlorides, 75% ammonia nitrogen (NH 3 -N), 40% phosphate (PO 4 -P), 93% most probable number (MPN) and 95% total viable count (TVC) reduction was achieved in the Biocache system. A comparative evaluation was done with the inferior surface fixed packing conduits and better treatment efficiency with lower wastage sludge biomass concentration was observed by the Bio-cache packed bed media. This study indicates a possibility of substantially effective attached growth system for small volume domestic wastewater treatment.

The use of aquatic macrophytes for the domestic wastewater treatment is increasing in various parts of the world. The aim of this study is to examine the potential of shallow pond system using water hyacinth (Echhornia crassipes) along with the microorganisms present in the bio-film attached to the roots and water column for treatment of domestic wastewater in the presence of high total dissolved solids (TDS) and heavy metal salts. The shallow pond system is different from conventional water hyacinth system and it has high oxygen rich zone to provide the superior growth of aerobic microorganism. The studies indicate that, water hyacinth can tolerate TDS up to 2000 mg/L in the shallow pond system. The heavy metal removal is a function of phytoaccumulation or phytoextraction, which can lead to morphological deformity if heavy metals exceed the saturation limit of 268 & 2152 mg/kg Cd, 381 & 3372 mg/kg Cu, 229 & 1850 mg/kg Ni, 462 & 2764 mg/kg Zn, in shoots and roots respectively. The reduction in TDS is marginal (19%) at the highest tolerable limit whereas the heavy metal reduction is 66%, 68%, 64%, 70% for Cd, Cu, Ni and Zn respectively at the outlet of the treatment system. The sewage treatment performance of the shallow pond water hyacinth system for all other parameters is estimated as 81% Chemical oxygen demand (COD), 91% Biochemical oxygen demand (BOD 5), 16% Total dissolved solids (TDS), 70% Total suspended solids (TSS), 4% Chlorides, 74% Ammonia nitrogen (NH 3-N), 41% Phosphate (PO 4-P), 96% Most probable number (MPN) and 98% Total viable count (TVC) reduction.