(WO9823541-A1)      The process of purifying waste water in two stages, with an unusual recycle, comprises anaerobic treatment produces biogas containing methane followed by a plantation water purification system is employed. A feature is introduced: biomass harvested from the second purification stage is recycled back into the waste water, before it enters the first stage.    USE -   A two-stage water purification process including a plantation, which recovers biogas.    ADVANTAGE -   This process treats waters having an organic loading in terms of chemical oxygen demand (COD) up to 500 mg/l, by digestion. A biogas product results. Gas recovered has a calorific value of 20-25 MJ/m3. Control of the first stage effluent loading, protects the second stage from overloading. Recycle and organic additions may be curtailed, to accommodate increasing influent loading. Whilst a variety of plants may be used, St. Augustine grass (stenotaphrum secundatum) is considered particularly robust and effective in this role. Biomass is comminuted in e.g. a commercial unit nominated in the patent.    (EP946432-A1)      The process of purifying waste water in two stages, with an unusual recycle, comprises anaerobic treatment produces biogas containing methane followed by a plantation water purification system is employed. A feature is introduced: biomass harvested from the second purification stage is recycled back into the waste water, before it enters the first stage.    USE -   A two-stage water purification process including a plantation, which recovers biogas.    ADVANTAGE -   This process treats waters having an organic loading in terms of chemical oxygen demand (COD) up to 500 mg/l, by digestion. A biogas product results. Gas recovered has a calorific value of 20-25 MJ/m3. Control of the first stage effluent loading, protects the second stage from overloading. Recycle and organic additions may be curtailed, to accommodate increasing influent loading. Whilst a variety of plants may be used, St. Augustine grass (stenotaphrum secundatum) is considered particularly robust and effective in this role. Biomass is comminuted in e.g. a commercial unit nominated in the patent.    (US6129844-A)      The process of purifying waste water in two stages, with an unusual recycle, comprises anaerobic treatment produces biogas containing methane followed by a plantation water purification system is employed. A feature is introduced: biomass harvested from the second purification stage is recycled back into the waste water, before it enters the first stage.    USE -   A two-stage water purification process including a plantation, which recovers biogas.    ADVANTAGE -   This process treats waters having an organic loading in terms of chemical oxygen demand (COD) up to 500 mg/l, by digestion. A biogas product results. Gas recovered has a calorific value of 20-25 MJ/m3. Control of the first stage effluent loading, protects the second stage from overloading. Recycle and organic additions may be curtailed, to accommodate increasing influent loading. Whilst a variety of plants may be used, St. Augustine grass (stenotaphrum secundatum) is considered particularly robust and effective in this role. Biomass is comminuted in e.g. a commercial unit nominated in the patent.    (EP946432-B1)      The process of purifying waste water in two stages, with an unusual recycle, comprises anaerobic treatment produces biogas containing methane followed by a plantation water purification system is employed. A feature is introduced: biomass harvested from the second purification stage is recycled back into the waste water, before it enters the first stage.    USE -   A two-stage water purification process including a plantation, which recovers biogas.    ADVANTAGE -   This process treats waters having an organic loading in terms of chemical oxygen demand (COD) up to 500 mg/l, by digestion. A biogas product results. Gas recovered has a calorific value of 20-25 MJ/m3. Control of the first stage effluent loading, protects the second stage from overloading. Recycle and organic additions may be curtailed, to accommodate increasing influent loading. Whilst a variety of plants may be used, St. Augustine grass (stenotaphrum secundatum) is considered particularly robust and effective in this role. Biomass is comminuted in e.g. a commercial unit nominated in the patent.