The waste water from food processing contains dissolved salts and organic matter. The amount of each depends upon the product being processed and the procedure being used. The suitability for irrigation of food processing waste water from 20 plants processing nine food products was assessed from the standpoint of electrical conductivity (EC), chloride and sodium concentrations, sodium-adsorption-ratio (SAR), and chemical oxygen demand (COD). Waste water from plants processing green beans (Phaseolus vulgaris L.), squash (Cucurbita pepo var. melopepo Alef.), tomatoes (Lycopersicon esculentum Mill.), corn (Zea mays L.), steam peeled potatoes (Solanum tuberosum L.) and sweet potatoes (Ipomoea batatas Lam.), and poultry is suitable for irrigation under most conditions. Waste water from some pea (Pisum sativum L.) and lima beans (Phaseolus lunatus L.) processing plants may be suitable for irrigation, but is of questionable suitability from others. Waste water from lye-peel potato processing is not suitable for irrigation.

Water pinch analysis and mathematical optimization are two approaches that can be used in an industrial unit to achieve the minimum water consumption and wastewater generation flowrates. The fundaments of these approaches are based on water reuse. In this study, water pinch analysis and mathematical optimization studies are conducted in a corn refinery to achieve minimum targets. COD and TDS were separately considered as single limiting contaminants in water pinch analysis and water network of a corn refinery plant was modified. Water consumption in the studied corn refinery decreased from 1800 m3/day to 1235 m3/day if COD was taken into account and to 1152 m3/day if TDS was. The same results are achieved for single contaminant in mathematical optimization as well. The single contaminant approaches in the most cases are useless due to process limitations in water reuse. Therefore, mathematical optimization with multi-contaminants approach is conducted to design a reasonable water distribution network. Simultaneous consideration of COD and TDS in a multi-contaminants optimization resulted in 30% decrease in water consumption and required freshwater was reduced to 1260 m3/day.

En este estudio se ha planteado la necesidad de evaluar el funcionamiento de proceso biológico utilizando tecnología MBR con el objeto de establecer las condiciones operacionales que permiten obtener un proceso de filtración en las diferentes circunstancias que puedan presentarse. | This study has raised the need to evaluate the performance of the biological process in order to establish operational conditions to obtain filtration process in different circumstances that may arise.

The effluent of food waste (FWE) is generated during food waste treatment process. It contains high organic matter content and is difficult to be efficiently treated. In this study, the sample was collected from a 200 t/d food waste treatment center in Hangzhou, China. Subcritical and supercritical water gasification were employed to decompose and convert FWE into energy. The effects of reaction temperature (300–500 °C), residence time (20–70 min) and activated carbon loading (0.5–3.5 wt%) on syngas production and the remaining pollutants in liquid residue were investigated. It was found that higher reaction temperature and longer residence time favored gasification and pollutant decomposition, resulting in higher H₂ production and gasification efficiencies. It is noteworthy that the NH₃-N was difficult to be converted and removed under current experimental conditions. The addition of activated carbon was found to increase the gasification efficiency. The highest total gas yield, H₂ yield, carbon conversion efficiency, gasification efficiency, total organic carbon removal efficiency and chemical oxygen demand removal efficiency were obtained from gasification at 500 °C for 70 min with 3.5 wt% activated carbon.

Microaeration has been used conventionally for the desulphurization of biogas, and recently it was shown to be an alternative pretreatment to enhance hydrolysis of the anaerobic digestion (AD) process. Previous studies on microaeration pretreatment were limited to the study of substrates with complex organic matter, while little has been reported on its effect on substrates with higher biodegradability such as brown water and food waste. Due to the lack of consistent microaeration intensities, previous studies were not comparable and thus inconclusive in proving the effectiveness of microaeration to the overall AD process. In this study, the role of microaeration pretreatment in the anaerobic co-digestion of brown water and food waste was evaluated in batch-tests. After a 4-day pretreatment with 37.5mL-O2/LR-d added to the liquid phase of the reactor, the methane production of substrates were monitored in anaerobic conditions over the next 40days. The added oxygen was consumed fully by facultative microorganisms and a reducing environment for organic matter degradation was maintained. Other than higher COD solubilization, microaeration pretreatment led to greater VFA accumulation and the conversion of other short chain fatty acids to acetate. This could be due to enhanced activities of hydrolytic and acidogenic bacteria and the degradation of slowly biodegradable compounds under microaerobic conditions. This study also found that the nature of inoculum influenced the effects of microaeration as a 21% and 10% increase in methane yield was observed when pretreatment was applied to inoculated substrates, and substrates without inoculum, respectively.

In this study, the suitability of an anaerobic biofilter (AnBF) as an efficient and low-cost wastewater treatment for safer irrigation water production for Sub-Saharan Africa was investigated. To determine the influence of different ubiquitous available materials on the treatment efficiency of the AnBF, rice husks and their pyrolysed equivalent, rice husk biochar, were used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal full-scale wastewater treatment plant pretreated with an anaerobic filter (AF) was used in this experiment. The filters were operated at 22 °C room temperature with a hydraulic loading rate of 0.05 m·h−1 for 400 days. The mean organic loading rate (OLR) of the AF was 194 ± 74 and 63 ± 16 gCOD·m−3·d−1 for the AnBF. Fecal indicator bacteria (FIB) (up to 3.9 log10-units), bacteriophages (up to 2.7 log10-units), chemical oxygen demand (COD) (up to 94%) and turbidity (up to 97%) could be significantly reduced. Additionally, the essential plant nutrients nitrogen and phosphorous were not significantly affected by the water treatment. Overall, the performance of the biochar filters was significantly better than or equal to the sand and rice husk filters. By using the treated wastewater for irrigating lettuce plants in a pot experiment, the contamination with FIB was >2.5 log-units lower (for most of the plants below the detection limit of 5.6 MPN per gram fresh weight) than for plants irrigated with raw wastewater. Respective soil samples were minimally contaminated and nearly in the same range as that of tap water.

This study investigated the effects of different water regimes in an acidogenic leach bed reactor (LBR) during 16-day batch mode food waste digestion. LBRs were operated under five water replacement ratios (WRRs) (100%, 75%, 50%, 25% and 5% in LBRs R1, R2, R3, R4 and R5, respectively) and methanogenic effluent (ME) addition with two leachate recirculation frequencies (once in 24h and 12h in LBRs R6 and R7, respectively). Results showed that 50–100% WRRs accelerated the hydrolysis and acidogenesis with butyrate as the dominant product (∼35% of COD); whereas 5–25% WRRs promoted propionate production. The ME recirculation enhanced protein decomposition and reduced ethanol production. Lactobacillus dominated in LBRs with water addition (R1–R5), while Clostridium and hetero-fermenting lactic acid bacteria dominated in LBR with ME addition (R7). The highest volatile solid degradation (82.9%) and methane yield (0.29L-CH4/g VS) were obtained with ME addition at 0.7d hydraulic retention time.