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On-site greywater treatment and reuse in urban areas bears the potential to reduce huge quantities of wastewater and lower freshwater shortages. Until now dissemination of small, single household applications has been rather limited as simple and high quality water producing, but also cost-effective treatment units have not been developed so far. This paper proposes a new process, based on a concurrently working hollow-fibre membrane as fixed biofilm support and filtration device. Bioreactor characteristics, influence of different aeration rates, membrane flux development, as well as structure and composition of biofilm were monitored to evaluate the performance of the tested pilot unit. The introduced process achieved international water reuse guidelines, worked soundly and could, compared to conventional micro MBR, significantly reduce energy demand (<1.4 kWh m(-3)). Fouling control by air scouring and chemical cleaning was not required once flux had stabilized. The biofilm analysis showed a porous, spongy-like structure. Microbiological investigation revealed a community of sheathed bacteria and nematodes that could play an important role in the flux stabilisation effect. In general, the study confirmed the suitability of the presented process for greywater treatment and provides valuable design data for future optimization and systematic analysis.

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Although in recent years new developments for smaller applications have been made, investment costs have decreased and fresh water and sewage fees have increased, it has not been published so far if there are feasible grey water systems for single households with high quality effluent on the market. This paper gives a general overview of grey water treatment systems, a detailed comparison of available advanced grey water treatment for single households and a cost evaluation in view of onsite membrane bioreactor (MBR) systems for single households. The data and information were collected from demo units, publications, manufacturers and suppliers of these systems and were compared with experiences found in research literature. Results show that on-site MBR systems with daily grey water reclamation of more than 500 litres (10 persons) could be costeffective. For single households the investment is still too high for a payback time of less than 15 years.

Arsenic in drinking water resources and, especially, in groundwater, represents a severe health problem for millions of people in affected regions. This paper investigates a removal technology combining non-thermal plasma at a reaction time of 30 min, which has improved the downstream coagulation and the filtration efficiency. The results show removal rates of total arsenic over 98%. In addition, WHO limits of less than 10 g / L could be achieved in both batch and continuous set-ups. A difference in effective over potential of the NTP reaction of 32 m V over a reaction using air as oxidant was calculated. Kinetic data of arsenic concentrations over time fitted a pseudo first-order reaction. The proposed process combination has shown to be a simple and energy-saving alternative compared to conventional oxidation and adsorption technologies by exploiting the ’enhancer’ effect of ozone and other reactive oxygen species within the NTP.

The study evaluates with a mechanistic model the pilot plant results of a combined moving bed biofilm process and membrane filtration (MBBMR) treating single household greywater. It mainly includes the simulation of reactor hydraulics, degradation of pollutants, development of biomass and settlement of sludge. Iterative calibration was made with steady-state results of a 10-month pilot test. The model shows good predictions of readily biodegradable chemical oxygen demand and ammonium removal, as well as biomass concentration on carriers and in suspension. Also, a sensitivity analysis was made which calculates the relative significance factor of each model coefficient and by this provides comparability with other studies. Simulation data and actually measured parameters show that the suggested process was rather independent of ambient temperatures and short-term load fluctuations. Obtained datasets and model structure could be of use for future designers, as well as sellers and users of this process for on-site greywater reclamation.