Augusto Arce

Cost comparison of full-scale water reclamation technologies with an emphasis on membrane bioreactors

The paper assesses the costs of full-scale membrane bioreactors (MBRs). Capital expenditures (CAPEX) and operating expenses (OPEX) of Spanish MBR facilities have been verified and compared to activated sludge plants (CAS) using water reclamation treatment (both conventional and advanced). Spanish MBR facilities require a production of 0.6 to 1.2 kWh per m3, while extended aeration (EA) and advanced reclamation treatment require 1.2 kWh per m3. The energy represents around 40% of the OPEX in MBRs. In terms of CAPEX, the implementation costs of a CAS facility followed by conventional water reclamation treatment (physical-chemical + sand filtration + disinfection) ranged from 730 to 850 €.m-3d, and from 1,050 to 1,250 €.m-3d in the case of advanced reclamation treatment facilities (membrane filtration) with a capacity of 8,000 to 15,000 m3d-1. The MBR cost for similar capacities ranges between 700 and 960 €.m-3d. This study shows that MBRs that have been recently installed represent a cost competitive option for water reuse applications for medium and large capacities (over 10,000 m3d-1), with similar OPEX to EA and conventional water reclamation treatment. In terms of CAPEX, MBRs are cheaper than EA, followed by advanced water reclamation treatment.

Nitrogen mineralisation in soil after addition of wine distillery waste compost: laboratory and field evaluation

The application of wastes from the wine-distillery industry as source of organic matter and nutrients could be a good option of agricultural management. This study is focused on soil nitrogen (N) mineralisation after addition of compost derived from this industry at different doses (7, 13 and 20 t ha–1). An aerobic soil incubation in controlled conditions was carried out to study N mineralisation from the soil-compost mixture as well as isolating the compost from the soil. The data were fitted to a non-linear regression obtaining low values of potentially mineralisable N (N0) and constants of mineralisation (k) (from 81 to 104 mg kg–1 and from 0.008 to 0.013 L day–1 for the soil-compost mixtures, and from 42 to 71 mg kg–1 and from 0.009 to 0.015 L day–1 for the increasing doses of compost) which indicates that it is a mature compost very resistant to mineralisation. Nitrogen mineralised (NM) in the field during two growing seasons (2011 and 2012) of a melon crop was calculated through a N balance, taking into account N inputs and outputs in the soil-plant system. NM in the unamended plots accounted to 31 kg ha–1 and 24 kg ha–1 in 2011 and 2012, respectively, and increased proportionally to the dose of compost applied until 113 kg ha–1 and 98 kg/ha in the consecutive years. The constants of mineralisation obtained in the laboratory were adjusted by field temperatures to predict NM in the field and a general overestimation was observed. The best estimates were obtained when considering the mixture of soil and compost, which reflects the important role of the soil to evaluate N mineralisation caused by the addition of organic wastes.