Mitigating salt accumulation in recycled brewery effluent through the integration of water treatment, agriculture and aquaculture

Water scarcity in South Africa, and globally, presents challenges for industries. It is imperative to develop responsible water use, such as recycling and reusing wastewater from food processing industries such as breweries. The Ibhayi Brewery (SAB Ltd) employs a combination of sustainable treatment processes that include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW) to treat brewery effluent on an experimental scale. The constituent concentrations of these experimentally treated effluents are within the ranges prescribed by local regulations to allow for potential downstream use in agriculture and aquaculture. However, the sodium content in this treated effluent, which originates from upstream cleaning agents and pH control at the onsite effluent treatment facility, is a constraint to the downstream use of brewery effluent. This study addresses the salt problem, by investigating the potential of either reducing/eliminating salt addition at source, or developing alternative techniques for downstream agriculture to mitigate the effects of salt accumulation caused by irrigation with brewery effluent. Four salt-tolerant test crops; Swiss chard (Beta vulgaris), saltbush (Atriplex nummularia), Salicornia meyeriana and sorghum (Sorghum bicolor), grew efficiently in brewery effluent irrigated soils but did not stop sodium accumulation in the growth medium. Swiss chard had the best growth with a wet biomass accumulation of 8,173 g m-2, due to the plant’s ability to tolerate saline conditions and continuous cropping. Crop rotation, to limit effects of nutrient depletion in soil, had no significant effect on plant growth suggesting soils were adequately able to provide micro-nutrients in the short-term. Prolonged irrigation with brewery effluent can lead to sodium accumulation in the soil, which was successfully controlled through the addition of soil amendments (gypsum and Trichoderma cultures). These reduced soil sodium from a potentially limiting level of 1,398 mg L-1 to the acceptable levels of 240 mg L-1 and 353 mg L-1 respectively, mainly through leaching. However only Trichoderma improved Swiss chard production to 11,238 g m-2. While crop rotation in this work did not contribute to mitigating the problem of salt accumulation, soil amended with Trichoderma appears to be a potential solution when brewery effluent is reused in agriculture. In an alternative to soil cultivation, CWs were trialled with no significant differences in the sodium concentration of brewery effluent treated along a 15 m lateral flow CW, which could be attributed to evapotranspiration. This was notably accompanied by a desirable 95.21% decrease in ammonia from inlet to outlet resulting in significant improvement in water quality for reuse in aquaculture where ammonia levels are important limiting constraints. While CWs remain a suitable brewery effluent treatment solution, this technology requires additional modelling and optimisation in order to mitigate the problem of salt accumulation in the reuse of treated brewery effluent in agriculture and aquaculture. This research demonstrates the baseline information for such modelling and optimisation. African catfish (Clarias gariepinus) grew in CW treated brewery effluent; however, this growth was moderate at 0.92% bw day-1, whereas Mozambique tilapia (Oreochromis mossambicus) were shown to be unsuited to growth in this system and lost weight with an average specific growth rate (SGR) of -0.98% bw day-1; and both fish species presenting with health related concerns. Hardy fish species such as African catfish can be cultured in brewery effluent, but with risk involved. This was a preliminary study to develop parameters for future dimensional analysis modelling to allow optimisation of the CW, based on nutrient removal rates obtained which will allow for improved downstream aquaculture by reducing or eliminating risks presented in this study. This work has also contributed to a foundation for the development of guidelines that use a risk-based approach for water use in aquaculture. Alternatives to the current in place cleaning agents were considered to mitigate the effects of salt accumulation. Sodium is introduced into the effluent via the use of sodium hydroxide and sodium chlorite for cleaning and disinfection in the brewery, as well as through effluent pH adjustment in the AD plant. The widespread use of outdated legacy cleaning systems and pH adjustment regimes is entrenched in the brewery standard operating procedures (SOP). A cost-benefit analysis (CBA) demonstrated that a change of cleaning and disinfecting regimes to hydrogen peroxide in the brewery, and magnesium hydroxide pH adjustment in the effluent treatment plant addresses the sodium issue upstream in the brewery practically eliminating sodium from the effluent. In addition, a life cycle analysis (LCA) was carried out to assess the environmental impacts associated with the alternative cleaning and pH adjustment scenarios. The LCA showed that electricity consumption during use phase of the chemicals for respective purposes, as well as their production activities were major contributors to the significant environmental impact categories that were assessed. The cleaning scenario employing the use of hydrogen peroxide for both cleaning and disinfection was found to be the most environmentally sustainable. This was attributed to the reduced number of chemicals used compared to the other cleaning scenarios. Dolomitic lime was the pH adjustment alternative with the lowest average environmental impact; but, however, had a higher impact on freshwater eutrophication which is of major concern if the effluent will be reused for irrigation. Magnesium hydroxide was therefore considered to be the better option as a sodium hydroxide alternative for pH adjustment. This mitigates salt accumulation, making treated brewery effluent suitable for reuse in high value downstream agriculture and aquaculture, while employing more environmentally sustainable technologies. Notably, this converts brewery effluent from a financial liability to Ibhayi Brewery, into a product containing water and nutrients that generate income, improve food security, and can create employment in downstream agriculture and aquaculture in a sustainable manner.

Biotreatment of brewery effluents for aquaculture use using autochthonous fungi

The potential of reducing environmental impact of untreated brewery effluent was investigated. Although concentrations of pollutants in such effluents are usually considered low and inadvertently discharged into adjacent urban drainage facility, mycoremediation to remove dissolved inorganic nutrients in effluent was conducted with a view for aquaculture use in Uyo metropolis, southeast Nigeria. Raw brewery effluents were obtained and screened for indigenous microbial flora. Autochthonous fungi isolated included Aspergillus niger, Verticillium sp. and Mucor sp. The potential use of isolates as alternative treatment of brewery effluents was analyzed for treated and control groups. Treated group was inoculated with pure colonies of fungi isolates while the control group received no fungi treatment or modification. Both groups were incubated for seven (7) days. Thereafter, the physicochemical parameters of raw and remediated effluents were analysed and compared with National Environmental Standards and Regulations Enforcement Agency (NESREA) and aquaculture standards. Results confirmed suitability of autochthonous fungi isolates in mycoremediation of brewery effluent for aquaculture and irrigation. Key words: effluent toxicity, industrial pollution, mycoremediation, aquatic ecosystem, Uyo

Post treatment of anaerobically treated brewery effluent using pilot scale horizontal subsurface flow constructed wetland system

The anaerobic process is considered to be a sustainable technology for the treatment of wastewaters rich in organic matter mainly due to its lower energy consumption and production of value-added products such as biogas and organic fertilizer. However, it cannot be seen as providing ‘complete’ environmental solution as its treated effluents would typically not meet the desired discharge limits in terms of residual carbon, nutrients and other pollutants. This has given impetus to subsequent post treatment in order to meet the environmental standards and protect the receiving water bodies and environment. The aim of this study was to evaluate the post-treatment potential of a pilot scale two-stage horizontal subsurface flow constructed wetland (HSSFCW) system planted with Cyperus alternifolius and Typha latifolia, respectively, for enhanced removal of residual carbon and nutrient from an up-flow anaerobic sludge blanket (UASB) reactor treated brewery effluent. A pilot scale two-stage HSSFCW was integrated with the UASB reactor, and its performance efficiency was assessed for the removal of total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), ammonium–nitrogen (NH4–N), total phosphorous (TP), and orthophosphate (PO43−). Macrophytes aboveground biomass and nutrient accumulation potential were also determined following standard methods. The results from this study showed that Cyperus alternifolius planted CW cell removed 68.5% TSS, 74.2% COD, 55.7% TN, 68.6% NH4–N, 41.1% TP and 48.1% PO43−. Moreover, further polishing with Typha latifolia planted CW cell enhanced the removal efficiencies to 89% TSS, 92% COD, 83.6% TN, 92.9% NH4–N, 74.4% TP, and 79.5% PO43−. Strong linearity and Pearson correlation was found between macrophyte biomass and nutrient accumulation in each CW cell (Cyperus alternifolius: R2 = 0.91, r = 0.97 for TN; R2 = 0.92, r = 0.96 for TP; and Typha latifolia: R2 = 0.96, r = 0.98 for TN and TP), and showed substantial nutrient reduction with cumulative nutrient accumulation of 1290 gTNm−2 and 708.7 gTPm−2 in the complete system. The performance of the pilot CW system as a tertiary treatment for brewery wastewater showed that the effluent meets the permissible discharge standards throughout the year excluding phosphorous.

Nutrient removal and carbohydrate production potential of indigenous Scenedesmus sp. grown in anaerobically digested brewery wastewater

Background The combination of nutrient removal using microalgae from wastewater with carbohydrate production has been considered as a promising approach for sustainable wastewater treatment and production of valuable products such as biofuels. In Ethiopia, urbanization and industrial development are not in tandem with wastewater treatment system The objective of this study was to evaluate nutrient removal and carbohydrate production potential of the indigenous microalgae Scenedesmus sp. grown in anaerobically digested brewery wastewater. The indigenous Scenedesmus sp. was grown in an anaerobically digested brewery effluent in different seasons of the year. The biomass was converted into carbohydrate using microwave, autoclave, and oven as pretreatment, followed by optimization for acid concentrations and hydrolysis time. Result The overall removal efficiencies for the indigenous Scenedesmus sp. based wastewater treatment system were over 99%, 92%, 63%, 65% and 75% for NH4+-N, TN, PO43− -P, TP and COD, respectively. The concentrations of final effluent quality of these parameters except for phosphorus nutrient were below the permissible discharge limit for brewery effluent standard set by Ethiopian Environmental Protection Authority. With regard to carbohydrate production, microwave-assisted acid hydrolysis with HCl produced a higher total sugar than that of autoclave and oven pretreatments. Among acid concentrations, HCl with 3 N produced a higher total sugar, which is significantly different (P < 0.05) to the other acid concentrations. The highest total sugar (233.89 mg g−1) was obtained from microalgal biomass during the 20 min hydrolysis time with 3 N HCl and 5% (w/v) biomass at 1000 watts and 1200C. Conclusions This study showed that there is an opportunity for using the indigenous microalgae for sustainable wastewater treatment and for carbohydrate production that uses as bioethanol source in Ethiopia.

Effect of pH on nutrient removal and crop production of hydroponic systems treating brewery effluent

The use of a crop to remove nutrients from brewery effluent and the influence of pH on these removal rates was evaluated. Cabbage (Brassica oleracea) was grown in recirculating hydroponic systems fed with post-anaerobically digested brewery effluent (BE) either subject to pH adjustment (6.5–7.0) or unaltered pH (8.0–8.5). These were compared with cabbages grown in water only and in a inorganic fertiliser nutrient solution (NS). Hydroponic systems fed with pH adjusted BE removed significantly more nitrogen and phosphorus than systems fed with pH unadjusted BE (p &lt; 0.05). The final weight of cabbages from the pH adjusted BE systems were 6.7 times greater than cabbages from the pH unadjusted BE systems, whereas pH adjustment had no influence on cabbage weight in the water-only and NS treatments. Anaerobically digested BE that is not pH adjusted is not a suitable water and nutrient source for the hydroponic production of cabbages. However, pH adjustment of BE renders it more suitable for hydroponic crop production with hydroponic systems decreasing dissolved inorganic nitrogen, ammonium, phosphate and chemical oxygen demand concentrations by 72.8, 31.8, 98.5 and 51.0%, respectively. Hydroponic systems can be used to treat post-anaerobically digested BE to a similar standard obtained by conventional activated sludge treatment system.