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Dissolved air flotation (DAF) waste, a byproduct with high lipid content separated from dairy wastewater, is disposed of by land spreading and causing environmental pollution. To develop a sustainable treatment for DAF waste, this study investigated the effects of food to inoculum (F/I) ratio and ultrasound pre-treatment on the anaerobic digestion of DAF waste. The biochemical methane potential (BMP) of tested DAF waste ranged from 436–566 mL CH 4 /g VS fed. Increasing the F/I ratio (>1.0) inhibited methane production due to long chain fatty acids (LCFA) accumulation, which high concentrations of oleate inhibited methanogenesis and delayed palmitate degradation. Ultrasound pre-treatment with 30 min pulse (10 s on/ 10 s off) and 15 min continuous operations increased soluble chemical oxygen demand in DAF waste by 82% and 52%, respectively. Moreover, continuous sonication removed 38% of LCFA due to the implosion of cavitation bubbles. The BMP of DAF waste increased by 36% after sonication with F/I ratio 3.0. However, the lag time of methane production was prolonged after sonication due to the fast release of LCFA to the bulk solution. By implementing ultrasound pre-treatment and optimizing the F/I ratio, the energy potential of DAF waste can be harnessed, leading to more sustainable practices in dairy production. [ABSTRACT FROM AUTHOR]

Dairy sludge is one of the main and inexpensive wastes of the dairy industry, which contains the nutrients necessary for the growth of lactic acid bacteria (LAB) to produce microbial metabolites, and for its efficient use, optimization of fermentation conditions is critical. In order to optimize the production of dry biomass, three independent variables of dairy sludge concentration (5, 12.5 and 20%), pH (6, 7 and 8) and the inoculation rate of Lactobacillus fermentum strain 4-17 (1, 3 and 5%) were used. Before fermentation, the cell growth and morphology of this bacterium were examined in order to determine the function of the growth rate and confirm the presence of bacteria in this medium. The independent variables were optimized using response surface method (RSM) with central composite design (CCD) in order to maximize dry biomass production by this bacterium. The optimization results showed that the maximum amount of dry biomass production related to the optimal treatment included 20% dairy sludge concentration, 1% inoculation rate and pH 8. Also, according to the results, the dairy sludge substrate is suitable for the fermentation of this bacterium. As a result, the effect of dairy sludge bed concentration and pH on dry biomass production by this bacteria was very significant. [ABSTRACT FROM AUTHOR]

The dairy sector in Bangladesh releases huge amounts of wastewater in the open environment. Dairy wastewater is enriched with hazardous contaminants, which can cause various health complications. The objective of this study was to evaluate the water quality of dairy wastewater by determining the physicochemical properties of tap water and wastewater from three farms from the Islamnagar zone, Savar, Dhaka, and also to assess the significant impacts of wastewater on the environment. The most important physicochemical properties investigated include pH, total dissolved solids (TDS), electrical conductivity (EC), dissolved oxygen (DO), and microbial colony count. The results revealed that in tap water, the pH ranged from 7.11 to 7.20, and in wastewater, it ranged from 7.30 to 7.77. The TDS in tap water ranged from 109 to 116 mg/L, and in wastewater, it ranged from 451 to 2000 mg/L. The EC values were found in tap water from 0.22 to 0.23 mS/cm, whereas in wastewater, they ranged from 0.86 to 13.20 mS/cm. Additionally, for DO, the tap water ranged from 4.21 to 6.25 mg/L; in wastewater, it ranged from 0.98 to 1.86 mg/L. The pH and TDS stayed within the standard limits in the physical–chemical parameters assessed. However, the EC and DO are not within the DoE (Department of Environment, Bangladesh)-allowed limits. In addition, more microbial colonies have occurred in wastewater than in tap water. The study demonstrates that the discharge of dairy wastewater in the open field is detrimental to our ecosystem, and a proper treatment facility is essential. [ABSTRACT FROM AUTHOR]

Dairy industries are highly polluting, energy and fresh water consuming installations. The present study aims to make dairy effluent treatment plant operation less time consuming with minimal energy consumption while generating a value added product. Analysis of the temporal and spatial variation in performance of a biofilm based plug flow reactor involved in the biotransformation of Dairy Waste Water (DWW) revealed ammonia (57.68 mg L–1) rich liquid biofertilizer production within 4 h, with associated reduction of nitrate (70.77%), phosphate (36.44%), protein (62.87%), Biological Oxygen Demand (BOD) (26.38%) and Chemical Oxygen Demand (COD) (39.59%). The process was 4 times faster than the fastest existing process reported till date. The consortium showed a striking reduction in its doubling time from 78 min 56 sec (in suspension culture) to 17 min 10 sec (as biofilm) upon immobilization. It could produce 734.60 mg ammonia per kg of immobilization matrix from DWW. Metagenomic analysis revealed the robustness of the biofilm based biotreatment system. The novelty of this study is the innovative approach of rapid conversion of the waste from dairy industry into a value added product using microbes from geosphere in an energy efficient manner which would make dairy effluent treatment plant operation self-sustainable and eco-protective. [ABSTRACT FROM AUTHOR]

In this research the membranes distillation were used to remove calcium ions from heavy sewers at dairy plants in Iraq. This method is easy to operate, easy to manage and has many economic benefits. A chemical treatment was carried out on it using alum as a coagulant, different tests achieved samples before and after passing MD, according to APHA, AWWA, WEF. The results showed that obtained in water treatment trust that has been manufactured and edited according to the characteristics of the water waste the interests of the dairy capacity of this method to remove the calcium ion to a certain extent it is when the concentration reaches the inside of this ion to 1428.57 mg per liter, where to start the composition of hydroxides of calcium responsible for pain. The optimal working temperature ranges from 20-22 ° C and the flow is around 0.66 kg.m-2.h-1, here was the result of a layer of plaster that led to clogged membrane and folding and was stopped for washing and cleaning. [ABSTRACT FROM AUTHOR]

Anaerobic dairy waste treatment requires effective control to avoid long-chain fatty acid (LCFA) inhibitory effects on anaerobic microorganisms, especially methanogens. The hybrid anaerobic baffled reactor (HABR) can provide system stability, but more needs to be done to understand how the microbial communities underpinning the HABR compartments behave and respond. Thus, this study aimed to examine the HABR's microbial community correlating its performance when subjected to an increase in organic loading rate (OLR) during simulated dairy wastewater treatment. Besides the elevation in OLR, the system could maintain a high COD removal efficiency, nearly to 91%, and elevate the methane production to 53%. Almost all of the organic matter removal occurred mainly in C1 and C2 compartments. The genera Methanosaeta, an acetoclastic methanogen, and Methanobacterium, a hydrogenotrophic methanogen, were the HABR's dominant species. The most representative phylum found was Bacteroidetes (12–28%), Firmicutes (3–20%), Chloroflexi (4–26%), and Proteobacteria (4–14%). Species capable of syntrophic partnership with methanogens were also identified, belonging to the family of Syntrophomonadaceae and Syntrophaceae. Microorganisms able to perform the AD process as HA73, VadinCA02, T78, Longilinea, Clostridium, and Syntrophomonas were present in the HABR. [ABSTRACT FROM AUTHOR]

In this study, Haematococcus pluvialis and Coelastrella saipanensis were evaluated for heterotrophic nutrition potential in dairy waste medium by blocking the PSII using DCMU. The study was done by four sets of experiments. In the first set, in the different concentrations DCMU-treatments, 20μL showed pronounced effect in H. pluvialis and C. saipanensis as 89 % and 83% decrease in cells (>30 and > 250 cells/mL) compared to control (536 ± 12.35 × 104 and 1167 ± 15.35 × 104 cells/mL, respectively). Damage to the PS II by DCMU interrupted the growth, which in turn produced a significant drop in the number of cells. In the second round of experiment, growth of algae in various dairy waste concentrations suggest that dairy wastewater (DWW) provides enough nutrients to produce 35.71 % and 64.74 % more cells in H. pluvialis and C. saipanensis, respectively compared to the control. In the third set, high DCMU concentration was added to microalgae cultures in DWW to assess the heterotrophic nutrition potential. Growth in cell number 34.4 ± 19 and 617.46 ± 60.44 cells/mL was recorded in H. pluvialis and C. saipanensis when grown control medium whereas addition of DCMU reduced the cell number to 1.53 ± 0.75 and 55.13 ± 0.75 cells/mL on 15th day, respectively. This shows cells in cultures treated with DCMU reveal that algae can sustain their metabolic activity by utilizing the nutrients of dairy waste inhibiting photosystem. Fourth round of experiments found that microalgae could resume their growth and productivity by adapting to heterotrophic nutritional behaviour when DCMU given in mild dose at different time interval. This study conclude as C. saipanensis grows more readily by absorbing dairy waste nutrients than H. pluvialis. Therefore, C. saipanensis is an excellent choice for wastewater treatment through sustainable environmentally benign process after scale-up investigation. These results provide useful information to advance to molecular study for measuring microalgae's capability for bioremediation application. [Display omitted] • Dairy waste nutrients are an efficient substrate for the growth of H. pluvialis and C. saipanensis. • These algae can thrive in the waste medium by utilizing the available nutrients by disabling phtosystem II using DCMU. • DCMU can be used to measure the microalgae capability of adaptation to heterotrophic nutrients. • In light of this, both algae, C. saipanensis in particular, is a good candidate for wastewater cleanup. [ABSTRACT FROM AUTHOR]

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Featured Application: This article deals with two different methods of wastewater treatment in the dairy industry. This article will help industrialists in the dairy world who have problems with their wastewater treatment. Membrane filtration can provide a significant role in the management of waste streams from food manufacturing operations. The objective of this research was to evaluate the reductions in the organic content of waste streams accomplished when using membrane filtration. Reductions in Chemical Oxygen Demand (COD) by membrane filtration were compared to a Dissolved Air Floatation (DAF) system. Membranes with six different pore sizes (200, 20, 8, 4, 0.083, and 0.058 kDa) were evaluated. In addition, the various membrane treatments were applied after the DAF as an additional level of comparison. The DAF treatment provided 75.15 ± 3.95% reduction in COD, and the reduction in COD improved from 85% to 99% as the membrane pore size decreased. When all membranes were used after a DAF pre-treatment, a reduction in COD to less than 1200 ppm in the permeate stream was achieved. These reductions were independent of the COD in the feed stream. The membrane fouling rates were evaluated for the membranes with the four largest pore-sizes membranes. The membranes with 20 kDa pore-size had the lowest fouling rates during extended fouling-rate studies. [ABSTRACT FROM AUTHOR]

The main objective of the present paper is to evaluate the use of Moringa oleifera (MO) as a natural coagulant in coagulation/flocculation/sedimentation (CFS) followed by the microfiltration (MF) or nanofiltration (NF) process in dairy wastewater treatment, focusing on determining the best association of treatments that can generate wastewater for reuse purposes. The association of CFS-MF-NF treatments showed a high removal efficiency for chemical oxygen demand (COD) (mean of 96%), turbidity, and color (mean of 99%) meeting water reuse standards, allowing the reutilization of the wastewater, in relation to the analyzed parameters. The results indicate a lower membrane fouling rate (63%), an increase in permeate flow, and better quality of the permeate, proving that the CFS-MF-NF treatment is the most suitable among all the tested treatments. Finally, the treated wastewater obtained with this process presents better quality than the wastewater obtained with the conventional treatments. [ABSTRACT FROM AUTHOR]

This paper presents a real-time control strategy based on the derivative of the oxi-reduction potential (ORP) values for nitrogen removal via nitrite in a sequencing batch reactor (SBR) fed with effluent from an anaerobic sequencing batch reactor (ASBR) treating dairy wastewater. The developed control strategy optimized the length of aerobic and anoxic phases without external carbon source addition. Firstly, a fixed interval length for aeration period was used in the SBR cycle to promote the nitrogen removal; however, this strategy did not allow the proper alternation of anoxic and aerobic conditions, and thus effective removal of nitrogen was not verified. After that, the real-time control strategy was implemented, and the end of nitrification and denitrification processes was determined when the derivative of the oxi-reduction potential (ORP) was close to zero. This strategy provided a removal of 92.2 ± 9.7 and 63.9 ± 19.0% for concentrations of TKN-N and Nt-N, respectively, which were well above those found for the open-loop system-43.8 ± 21.6 and 26.5 ± 26.2% for the removal of TKN-N and Nt-N, respectively. [ABSTRACT FROM AUTHOR]

Dairy wastewater collected from local dairy industry was used as a growth media (without any pre-treatment) for the cultivation of microalgae Acutodesmus dimorphus . The level of COD reduced over 90% (from 2593.33 ± 277.37 to 215 ± 7.07 mg/L) after 4 days of cultivation; whereas, ammoniacal nitrogen was consumed completely (277.4 ± 10.75 mg/L) after 6 days of cultivation. Dry biomass of 840 and 790 mg/L was observed after 4 and 8 days of cultivation, respectively, which is about 5–6 times more than that of BG-11 grown culture (149 mg/L after 8 days). This biomass contains around 25% lipid and 30% carbohydrate, which can be further converted into biodiesel and bioethanol, respectively. Theoretical calculations based on the recently reported conversion yield suggest that 1 kg biomass of A. dimorphus might produce around 195 g of biodiesel and 78 g of bioethanol, which sums up to 273 g of biofuels. [ABSTRACT FROM AUTHOR]

In sequencing batch reactors (SBRs) treating dairy wastewaters, the overgrowth of filamentous bacteria is a frequent cause of operational problems. The present study aimed at understanding to what extent the operating conditions of a SBR can be optimized to convert a bulking activated sludge into a well-settling biomass at low aeration velocity. The abundance of filament morphotypes and floc-formers able to store biopolymers were analysed by PCR-DGGE and 16S amplicon sequencing. The results indicated that a combination of an anaerobic-microaerated feeding pattern with a low selective pressure was beneficial to supress filamentous overgrowth and to form aerobic granules, while increasing the efficiency of suspended solid removal. Average removal efficiencies for total chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were 94 ± 2%, 95 ± 1% and 83 ± 13%, respectively. [ABSTRACT FROM AUTHOR]

A dairy wastewater treatment system composed of the 1st segment (no aeration) equipped with a facility for the destruction of milk fat particles, four successive aerobic treatment segments with activated sludge and a final sludge settlement segment was developed. The activated sludge is circulated through the six segments by settling sediments (activated sludge) in the 6th segment and sending the sediments beck to the 1st and 2nd segments. Microbiota was examined using samples from the non-aerated 1st and aerated 2nd segments obtained from two farms using the same system in summer or winter. Principal component analysis showed that the change in microbiota from the 1st to 2nd segments concomitant with effective wastewater treatment is affected by the concentrations of activated sludge and organic matter (biological oxygen demand [BOD]), and dissolved oxygen (DO) content. Microbiota from five segments (1st and four successive aerobic segments) in one location was also examined. Although the activated sludge is circulating throughout all the segments, microbiota fluctuation was observed. The observed successive changes in microbiota reflected the changes in the concentrations of organic matter and other physicochemical conditions (such as DO), suggesting that the microbiota is flexibly changeable depending on the environmental condition in the segments. The genera Dechloromonas , Zoogloea and Leptothrix are frequently observed in this wastewater treatment system throughout the analyses of microbiota in this study. [ABSTRACT FROM AUTHOR]

Activated carbons (MBK400 and MBK600), produced from milk bush kernel shells, were carbonized at 400 and 600°C, respectively, activated with H3PO4, and subsequently, employed to remove heavy metals (cadmium, lead, nickel, zinc, iron, and copper) in dairy industrial wastewater (DIWW). Effects of doses (1.0–3.0 g/L) and contact time (5–25 min) at constant agitation (120 rpm) on removal efficiencies and adsorption capacities of the agricultural precursors were investigated. Four types of Langmuir isotherm model were used to fit the adsorption of the heavy metals. The pH of the treated DIWW increased from 6.1 to a range of 6.7–6.9 and 6.8–6.9 with MBK400 and MBK600, respectively, while, there were slight increase in the conductivity of the treated DIWW, except with 3.0 g of MBK400, which reduced the conductivity from 377 to 345 µS/cm. The maximum percentage of cadmium, iron, copper, lead, zinc and nickel removal were 90, 80, 91.7, 91.6, 87.18, and 73.62% with 2.0 g/L MBK400, 1.0 g/L MBK400, 3.0 g/L MBK600, 2.0 g/L MBK600, 3.0 g/L MBK600 and 1.0 g/L MBK600, respectively. The removal of lead ranked the highest, consistently, for all the doses of MBK400 and MBK600 used. The Langmuir Type-1 was the most suitable linearized Langmuir isotherm that described the adsorption of the heavy metals in the DIWW, based on coefficient of determination (R2). The adsorbents developed are suitable for the removal heavy metals, particularly lead, in a typical DIWW. [ABSTRACT FROM PUBLISHER]

In this study, the potential of MEUF process has been analyzed to treat a real dairy wastewater. For this purpose, linear alkylbenzene sulfonate (LAS) and Triton X-100 (TX-100) have been used as anionic and nonionic surfactants, respectively. The ranges of 2–3.5 bars and 0–4 mM are selected for transmembrane pressure (TMP) and surfactants concentration, respectively, to investigate their effects on the permeate flux as a function of operating time. Moreover, it is revealed experimentally that rejection of pollution indices including chemical oxygen demand (COD) and total dissolved solid (TDS) is affected by TMP and feed surfactant concentration, while turbidity is remained relatively unchanged. According to the experimental results analysis, the increase of feed surfactant concentration has negative and positive effects on the permeate flux and rejection efficiency, respectively. TMP enhancement also leads to the higher flux values but it does not necessarily improve the rejection. Furthermore, the effectiveness of anionic surfactant in pollution indices elimination is more than the nonionic one. In the treatment combination assessed for the factors, the best rejection values of COD, TDS, and turbidity using LAS surfactant with polyacrylonitrile (PAN-350) 20-kDa poly(ethylene glycol) membrane are almost 93, 52, and 99.9%, respectively. [ABSTRACT FROM AUTHOR]

Based on its large water consumption, dairy industry is considered as one among the most polluting food industries. The present work is related to investigations about water management practices in one Tunisian dairy plant where two effluents’ generators were identified as the most polluting following their COD assessment. The first was the generated water from DECREAMING (D) machines washings with COD value of 112 g L−1, and the second source is BACTOFUGATE (B) with COD value of 196 g L−1. Thermal coagulation was performed for (D) and (B) samples leading to media clear phase separation. After decantation, recuperated supernatants were filtrated. The recorded COD removal amount exceeded 90% for both samples filtrates. Additional biological treatment was performed with mediums based on the obtained filtrates. IsolatedCandidastrains,Lactobacillusand baker’s yeast strains were inoculated in batch process fermentation. Different biological treatment effects were evaluated using musts COD assessment at the end of fermentation after biomass removal. The reduction in organic load was important with the appropriate inoculated strains. [ABSTRACT FROM AUTHOR]

Dairy industries and milk processing plants normally discharge their wastes directly to the close surroundings, generating environmental nuisances. Consequently, dairy wastewater deserves special attention since its levels of potential contaminants typically exceed those levels considered hazardous for domestic wastewater. At present study, performance of conventional chemical coagulation using poly aluminum chloride as an inorganic pre-polymerized coagulant (at various pH and coagulant dosages) and adsorption process by modified dried activated sludge (with ZnCl2) for treatment of real dairy wastewater was investigated. Maximum removal efficiency of pollutants (BOD5and chemical oxygen demand (COD)) by chemical coagulation process was achieved at initial pH 8 and coagulant dose 100 mg/L in 60 min. In addition, optimum conditions for adsorption process were found to be: initial pH 6, adsorbent dose of 7 g/L, and contact time 90 min. The biosorption equilibrium data were fitted by Freundlich isotherm. Furthermore, according to the thermodynamic properties, ΔG°, ΔH°, and ΔS°, adsorption of COD onto modified dried activated sludge was spontaneous, endothermic, and feasible in the temperature range of 298–318 K. [ABSTRACT FROM PUBLISHER]

Dairy wastewater when released from the industry is highly rich in organic matter, suspended solids, oil and grease, fats, nitrogen, phosphorous and calcium. After disposal it may cause water as well as land eutrophication and can block soil pores thus resulting in reduced levels of soil infiltration. When send to the treatment units this dairy wastewater also results in crystalline deposits. Dairy wastewater is classified as nutrient rich wastewater containing sufficient amount of nitrogen, phosphorous and calcium that can be separated or extracted by suitable methods. The extraction of these nutrients is done using a lab scale batch reactor of desired efficiency needful to justify this issue and find a solution to it. The process of extraction of nutrients is performed using a Mixed Suspension Mixed Product Removal Batch Reactor of suitable dimensions in the form of Magnesium Ammonium Phosphate and Hydroxyapatite. These nutrients being a slow released fertilizer will provide value to the crop production and land yield, further reducing BOD, COD and TSS of the wastewater making it safer to dispose. Dairy wastewater is taken from an industrial source which is firstly characterized, diluted and then fed into the reactor in the presence of suitable seed material resulting in formation of crystals. Experiments performed for the formation of Magnesium Ammonium Phosphate and Hydroxyapatite are separately carried out in different batches. The key focus of this project is to enhance the efficiency of dairy wastewater treatment units and prevent crystallization during treatment process. [ABSTRACT FROM AUTHOR]

This study demonstrated that the limiting factor to algae growth on dairy wastewater was the ammonia nitrogen deficiency. Dairy wastewaters were mixed with a slaughterhouse wastewater that has much higher ammonia nitrogen content. The results showed the mixing wastewaters improved the nutrient profiles and biomass yield at low cost. Algae grown on mixed wastewaters contained high protein (55.98–66.91%) and oil content (19.10–20.81%) and can be exploited to produce animal feed and biofuel. Furthermore, algae grown on mixed wastewater significantly reduced nutrient contents remained in the wastewater after treatment. By mitigating limiting factor to algae growth on dairy wastewaters, the key issue of low biomass yield of algae grown on dairy wastewaters was resolved and the wastewater nutrient removal efficiency was significantly improved by this study. [ABSTRACT FROM AUTHOR]

Anaerobic sequencing batch reactors applied to the treatment of dairy wastewaters have received increasing attention in bench-scale studies, particularly because dairy plants intermittently operate. This study compared two mechanically stirred, pilot-scale reactors, the Anaerobic Sequencing Batch Reactor (ASBR) and the Anaerobic Sequencing Biofilm Batch Reactor (ASBBR), in the treatment of dairy-plant wastewater. The reactors were fed with wastewater from a dairy plant and were operated with two cycle times: 48 and 24 h. The organic matter concentration in the influent, measured as chemical oxygen demand (COD), was approximately 4500 mg l −1 . The ASBR exhibited highly efficient removal of organic matter (92.8 ± 5.9%), with production of bicarbonate alkalinity and low concentration of volatile fatty acids in the effluent for both cycle times. In contrast, the organic matter removal efficiency of the ASBBR decreased from 92.3 ± 16.5% to 60.5 ± 16.5% when the cycle time was changed from 48 h to 24 h. Moreover, the ASBBR also presented higher levels of instability during operation, showing lower bicarbonate alkalinity concentrations and higher concentrations of volatile fatty acids in the effluent when compared with the ASBR. The superior results exhibited by the ASBR may be related to larger changes in its microbial ecology and biomass configuration that occurred because of its better microbial selection and adaptation conditions. Granule diameters decreased greatly over time; however, this reduction did not affect settleability, assuring the performance of the ASBR. [ABSTRACT FROM AUTHOR]

In this study, response surface methodology approach using Central Composite Design was applied to develop a mathematical model and to optimize process parameters for the COD, color, orthophosphate, TSS, and turbidity removal from dairy wastewater by electrocoagulation process using iron and aluminum electrodes. The second-order regression model was developed to predict the removal efficiencies using Statgraphics Centurion XVI.I software program. The optimum conditions for the COD removal were found to be 5.06 min for reaction time, 5.0 for pH, and 50.5 A/m2for current density with Al electrodes, whereas 5.21 min for reaction time, 5 for pH, and 65 A/m2for current density with Fe electrodes. High removal efficiencies (98.91% COD and 99.78% orthophosphate removal with Al electrodes, and 98.84% COD and 98.24% orthophosphate removal with Fe electrodes) were achieved under optimum conditions. The operating costs for the COD removal from dairy wastewater by electrocoagulation process using Fe and Al electrodes at optimized conditions were calculated to be 0.54 and 0.42 €/m3, respectively. The sludge formed under optimized conditions in EC process was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The FT-IR results showed that pollutants in dairy wastewater were linked with aluminum hydroxide and iron hydroxide complexes, precipitated at the bottom of the reactor containing milk components. [ABSTRACT FROM PUBLISHER]

The biomass productivity and nutrient removal capacity of simultaneous Chlorella sp. cultivation for biodiesel production and nutrient removal in raw dairy wastewater (RDW) in indoor bench-scale and outdoor pilot-scale photobioreactors were compared. Results from the current work show that maximum biomass productivity in indoor bench-scale cultures can reach 260 mg L −1 day −1 , compared to that of 110 mg L −1 day −1 in outdoor pilot-scale cultures. Maximum chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) removal rate obtained in indoor conditions was 88.38, 38.34, and 2.03 mg L −1 day −1 , respectively, this compared to 41.31, 6.58, and 2.74 mg L −1 day −1 , respectively, for outdoor conditions. Finally, dominant fatty acids determined to be C16/C18 in outdoor pilot-scale cultures indicated great potential for scale up of Chlorella sp. cultivation in RDW for high quality biodiesel production coupling with RDW treatment. [ABSTRACT FROM AUTHOR]

The present work describes an effectiveness of ultrasonication pretreatment for enhancement of biohydrogen production from complex dairy wastewater at optimized culture conditions obtained previously. An ultrasonic pretreatment was comprised of five ultrasonic densities (UD) (from 0 to 0.2 W/mL) at five different ultrasonication time (UT) (from 6 to 14 min). Response surface methodology (RSM) analysis showed that UD was the highly significant parameter, which predominantly influences biodegradability, hydrogen yield (HY), and specific hydrogen production rate (SHPR) enhancement during dark fermentation. Optimization of pretreatment using RSM integrated with desirability function followed by a verification test showed that maximum HY of 15.33 mmol/g COD and SHPR of 31.38 mmol/g VSS.d obtained at 0.08 W/mL and 9 min. Significant relative enhancement of HY, 27%, and SHPR, 51%, suggests that ultrasonication pretreatment of complex dairy wastewater is about 1.1–2-fold more effective for enhanced hydrogen recovery compared to unsonicated one. A successful energy balance of ultrasonication pretreatment suggests an effectiveness of the pretreatment for enhanced energy recovery. [ABSTRACT FROM AUTHOR]

To overcome the shortcomings of direct anaerobic digestion of the dairy waste effluent, an enzymatic pre-treatment have been employed to significantly overcome the sludge problems and other drawbacks. This work describes the application of Lipase Z to perform the enzymatic pre-hydrolysis of a synthetic dairy wastewater containing around 2,000 mg/mL of fat content. Different process parameters like effect of enzyme loading, temperature, different concentration of fats and different concentrations of NaCl were optimized for maximum conversion of fat. The maximum hydrolysis of around 75% is achieved at 0.2% w/v enzyme loading, 30°C and 100mM NaCl concentration for 2,000 mg/mL fats content. It was contemplated that the enzymatic pre-hydrolysis prior to the anaerobic digestion reduced the reaction time required for anaerobic degradation, improved biogas formation and appreciative chemical oxygen demand removal. [ABSTRACT FROM AUTHOR]

Dairy wastewater is characterized by a high content of hardly biodegradable dissolved, colloidal, and suspended organic matter. This work firstly investigates the performance of two individual electrochemical treatments, namely electrocoagulation (EC) and electro-oxidation (EO), in order to finally assess the mineralization ability of a sequential EC/EO process. EC with an Al anode was employed as a primary pretreatment for the conditioning of 800 mL of wastewater. A complete reduction of turbidity, as well as 90 and 81 % of chemical oxygen demand (COD) and total organic carbon (TOC) removal, respectively, were achieved after 120 min of EC at 9.09 mA cm. For EO, two kinds of dimensionally stable anodes (DSA) electrodes (Ti/IrO-TaO and Ti/IrO-SnO-SbO) were prepared by the Pechini method, obtaining homogeneous coatings with uniform composition and high roughness. The OH formed at the DSA surface from HO oxidation were not detected by electron spin resonance. However, their indirect determination by means of HO measurements revealed that Ti/IrO-SnO-SbO is able to produce partially physisorbed radicals. Since the characterization of the wastewater revealed the presence of indole derivatives, preliminary bulk electrolyses were done in ultrapure water containing 1 mM indole in sulfate and/or chloride media. The performance of EO with the Ti/IrO-TaO anode was evaluated from the TOC removal and the UV/Vis absorbance decay. The mineralization was very poor in 0.05 M NaSO, whereas it increased considerably at a greater Cl content, meaning that the oxidation mediated by electrogenerated species such as Cl, HClO, and/or ClO competes and even predominates over the OH-mediated oxidation. The EO treatment of EC-pretreated dairy wastewater allowed obtaining a global 98 % TOC removal, decreasing from 1,062 to <30 mg L. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ultrasound used for the intensification of enzyme pretreatment of dairy waste water. [•] Effect of various parameters on ultrasound assisted enzyme catalyzed reaction of fat was studied. [•] COD was decreased from 42,400ppm to 11,250ppm with 73.5% removal efficiency. [•] Ultrasound alone significantly reduce the reaction time by 97%. [Copyright &y& Elsevier]

The wastewater from the dairy industries usually contains high concentrations of contaminants and, since the volume generated is also high, the total contaminant load is very significant. Among the available options for treatment, biological degradation looks like the most promising one. Furthermore, the supplementation of the native microbial populations with external microorganisms with high specific degradation rates (bio-augmentation) has demonstrated to improve the performance of treatment. The main objective of this research was to select a combination of bacteria to improve the aerobic treatment of dairy processing wastewater. For this purpose, eleven fat/protein-degrading microorganisms belonging to the genera Bacillus, Serratia, Lactococcus, Enterococcus, Stenotrophomonas, Klebsiella and Escherichia, were evaluated as potential degrading bacteria using a Plackett-Burman design. Assays were carried out to select the strains that most significantly influenced the degradation of wastewater and biomass yield, in terms of COD removal. A simulated dairy industry effluent was used as culture medium. Four strains were selected as potential members of the microbial consortium: Lactococcus garvieae, Bacillus thuringiensis, Escherichia coli and Stenotrophomonas sp. The optimal operation temperature and pH range of the selected consortium were 32°C and 6 ∼ 8, respectively. The degradation percentages reached with the selected consortium were 80.67 and 83.44% at 24 and 48 h, respectively. The selected consortium significantly improved the degradation of the dairy wastewater, and the degradation degree achieved by this consortium was higher than by using the strains individually. [ABSTRACT FROM AUTHOR]

Abstract: Present work describes a kinetic analysis of various aspects of biohydrogen production in batch test using optimized conditions obtained previously. Monod model and Logistic equation have been used to find growth kinetic parameters in batch test under uncontrolled pH. The values of μ m , K s , and X m were 0.64 h−1, 15.89 g-COD L−1, and 7.26 g-VSS L−1, respectively. Modified Leudeking-Piret and Michaelis–Menten equation corroborates a flux of energy to hydrogen production pathway and energy sufficiency in the system. Modified Gompertz equation illustrates that the overall rate and hydrogen yield at 15 g-COD L−1 was higher compared to a dark fermentation of other wastewaters. Besides, Andrew's equation also suggests that since the higher value of K I (19.95 g-COD L−1), k (255 mL h−1 L−1) was not inhibited at high S. The experimental results implied that the entire products during the fermentation process were growth and substrate degradation associated. The result also confirms that the acetate and butyrate were substantially used for hydrogen production in acidogenic metabolism under uncontrolled pH. [Copyright &y& Elsevier]

Abstract: In this study, the granular sludge was generated for simultaneous nitrification, denitrification and phosphorus removal (SNDPR) and studied on a laboratory scale. Analyzing the nutrients removal percentages from wastewater were scrutinized by using an optimization of the variables, i.e., COD:N:P ratio, OLR, aeration time, MLSS, F:M and HRT. These 6 interrelated parameters were evaluated as the process response. Microscopic observations of the performance of the SNDPR process revealed that the granules included Bacillus sp. in the bacterial community. According to these results, the UAASB system produced an effluent that lends dairy wastewater suitable for land irrigation and that this an attractive process of using granular sludge is appropriate for achieving carbon, nitrogen and phosphorus removal from nutrient-rich wastewater by a biological method. [Copyright &y& Elsevier]

A fungal consortium including Aspergillus niger, Mucor hiemalis and Galactomyces geotrichum was tested for the treatment of dairy wastewater. The bio-augmentation method was tested at lab-scale (4 L), at pilot scale (110 L) and at an industrial scale in Wastewater Treatment Plants (WWTP). The positive impact of fungal addition was confirmed when fungi was beforehand accelerated by pre-culture on whey (5 g/L lactose) or on the dairy effluent. Indeed, chemical oxygen demand (COD) removal yields increased from 55% to 75% for model medium, diluted milk. While after inoculation of an industrial biological tank from a dairy factory with the fungal consortium accelerated by pre-cultivation in a 1000 L pilot plant, the outlet COD values decreased from values above the standard one (100 mg/L) to values in the range of 50–70 mg/L. In addition, there was a clear impact of fungal addition on the ‘hard’ or non-biodegradable COD owing to the significant reduction of the increase of the COD on BOD 5 ratio between the inlet and the outlet of the biological tank of WWTP. It was in the range of 451%–1111% before adding fungal consortium, and in the range of 257%–153% after bio-augmentation with fungi. An inoculated bioreactor with fungal consortium was developed at lab-scale and demonstrated successfully at pilot scale in WWTP. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combined UASB–MBR is feasible for dairy wastewater treatment at ambient temperatures. [•] The system presented a high tolerance to loading changes and temperature fluctuations. [•] High biogas production with more than 70% methane content was obtained. [•] Overall biomass yield similar to anaerobic systems was obtained. [•] Permeability values similar to those reported for aerobic MBR systems were obtained. [ABSTRACT FROM AUTHOR]

Highlights: [•] Investigate the environmental fate of 17α-estradiol-3-sulfate in dairy wastewater. [•] Compare aerobic and anaerobic degradation rates of estrogen 17α-estradiol-3-sulfate. [•] Explore aerobic and anaerobic degradation mechanisms of the estrogen in wastewater. [•] Assess the potential risk of using dairy wastewater for agricultural irrigation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dairy wastewater was treated in an industrial three-cascade-reactor plant. [•] The plant maintained high treatment performances over a wide range of influent loads. [•] The large majority of the organic matter depletion occurred in the first reactor. [•] At high organic loads of the influent DO and ORP were very low in the first reactor. [•] Values of the sludge volume index indicated good settling properties of the flocs. [ABSTRACT FROM AUTHOR]

The application of batch systems to the direct treatment of dairy wastewater was investigated. Batch experiments were conducted to study the organics removal and simultaneous nitrification and denitrification (SND) process. The experiment was conducted by varying four independent parameters (mixed liquor suspended solids, chemical oxygen demand [COD]/N ratio, aeration time and cycling time), using a central composite design under response surface methodology. The process responses of five dependent parameters (COD, Total kjehldahl nitrogen (TKN), NO3-, effluent NO3- and effluent total nitrogen) were studied, and in each case, the percentage removal in batch runs was determined with each process displayed in contour plots. Finally, after optimizing the process conditions, the best treatment of dairy wastewater under optimized conditions was established and the responses were shown. This study shows that microbial granules cultivated under the alternating aerobic/anaerobic conditions in batch systems could efficiently remove organic carbon and convert all the ammonium to nitrogen gas. [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous nitritation and anammox is a novel process for nitrogen removal from wastewater. This study operated two innovative biofilters to examine the effects of pH and temperature on the nitritation–anammox process. Marble chips were packed in the biofilters to buffer pH and supplement alkalinity. Electric arc furnace slag was added to marble chips in one biofilter to further increase pH to favor nitritation over nitratation. After a 5-month startup period, the biofilters were batch loaded with dairy wastewater and drained weekly over seven months. Fluorescence in situ hybridization analysis found that aerobic ammonium oxidizing and anammox bacteria accounted for 69–74% of the bacterial populations in the biofilters, which were substantially higher than those reported earlier for constructed wetlands and biofilters. Ammonium removal rate was significantly higher in the biofilter at pH 8.1 (7.8±1.2gN/m3 d) than that in the other biofilter at pH 7.6 (6.4±1.3gN/m3 d). Free ammonia concentration should be controlled along with pH to avoid toxicity to anammox bacteria. There was no significant correlation of nitrogen removal with the seasonal variation of temperature. Temperature effects were further examined for another five months by heating one of the biofilters. Ammonium removal rate was greater (23.7±3.3gN/m3 d) in the heated biofilter at 28.8±1.1°C than that in the unheated biofilter (7.6±2.4gN/m3 d) where temperature fluctuated at 21.2±3.2°C. The effects of constant temperature were superior to pH effects on nitritation–anammox. The nitritation–anammox process is more sensitive to temperature than nitritation and anammox individually. This study demonstrated that waste products (marble chips and furnace slag) can be used in biofilters to effectively raise pH and enhance nitritation–anammox for nitrogen removal from dairy wastewater. [Copyright &y& Elsevier]

As one of the new techniques in the field of sludge treatment, ultrasonic wave irradiation could be employed to release nutrients from the solids to the soluble phase, which can subsequently be degraded by microorganisms in biological treatment. In this paper the Tehran Pegah Dairy Complex was selected to evaluate the effect of ultrasonic wave irradiation on soluble chemical oxygen demand (SCOD), nitrogen content, phosphors content, and also the causes of rising temperature of waste-activated sludge. Experimental investigation was carried out at 60, 120, 240, and 480 s contact times, and at output powers of 100, 300, and 500 W with 20 kHz operational frequency. Results revealed that the highest temperature was found around 12°C at 500W output power and 480s contact time. Hydrolysis of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) also showed increasing trends at all different contact times. At 480 s contact time, the maximum of TP and TKN release was about 116% and 170%, which was observed at 500W and 100W. The maximum release of COD was found around 640%, which was observed at 300W output power. [ABSTRACT FROM AUTHOR]

Abstract: Constructed wetland systems (CWS) have been used as a low cost bio-filtration system to treat farm wastewater. While studies have shown that CWS are efficient in removing organic compounds and pathogens, there is limited data on the presence of hormones in this type of treatment system. The objective of this study was to evaluate the ability of the CWS to reduce estrogenic and androgenic hormone concentration in dairy wastewater. This was achieved through a year long study on dairy wastewater samples obtained from a surface flow CWS. Analysis of hormonal levels was performed using a solid phase extraction (SPE) sample clean-up method, combined with reporter gene assays (RGAs) which incorporate relevant receptors capable of measuring total estrogenic or androgenic concentrations as low as 0.24 ng L−1 and 6.9 ng L−1 respectively. Monthly analysis showed a mean removal efficiency for estrogens of 95.2%, corresponding to an average residual concentration of 3.2 ng L−1 17β-estradiol equivalent (EEQ), below the proposed lowest observable effect concentration (LOEC) of 10 ng L−1. However, for one month a peak EEQ concentration of 115 ng L−1 was only reduced to 18.8 ng L−1. The mean androgenic activity peaked at 360 ng L−1 and a removal efficiency of 92.1% left an average residual concentration of 32.3 ng L−1 testosterone equivalent (TEQ). The results obtained demonstrate that this type of CWS is an efficient system for the treatment of hormones in dairy wastewater. However, additional design improvements may be required to further enhance removal efficiency of peak hormone concentrations. [Copyright &y& Elsevier]

Abstract: The significant improvements of membrane technology in reliability and cost effectiveness have increased the reuse probability and recycling extent of dairy wastewater. However, membrane fouling still remains a major bottleneck in wide application. In order to solve the problem, this paper investigated the possibility and applicability of coagulation-membrane bioreactor (MBR) hybrid system in reclaiming dairy wastewater. A comparative experiment based on the removal efficiencies and the membrane performance was designed to achieve the purpose. The results showed that polyaluminium chloride as the appropriate coagulant in coagulation process was effective for turbidity removal. Coagulation process played a very important role in stabilizing the effluent of MBR and the level of transmembrane pressure. MBR was a crucial process in turbidity and aluminum removal. MBR had the capability to resist shock loading and to maintain the high COD removal. Biological flocs in MBR could improve the fouling level of membrane. The hybrid system reduced 98% COD from the original and COD value of the wastewater came down to 8mg/L. The combination of coagulation with MBR presents the possibility and applicability to reclaim effluent in dairy industries. [Copyright &y& Elsevier]

Abstract: The dairy industry is generally considered to be the largest source of food processing wastewater in many countries. The highly variable nature of dairy wastewaters in terms of volumes and flowrates and in terms of high organic materials contents such as COD 921–9004mgL−1, BOD 483–6080mgL−1, TN of 8–230mgL−1 and SS of 134–804mgL−1 makes the choice of an effective wastewater treatment regime difficult. A high performance bioreactor, an aerobic jet loop reactor, combined with a ceramic membrane filtration unit, was used to investigate its suitability for the treatment of the dairy processing wastewater. The oxygen transfer rates of the bioreactor were found to be very high (100–285h−1) on the operating conditions. A loading rate of 53kgCODm−3 d−1 resulted in 97–98% COD removal efficiencies under 3h hydraulic retention time. The high MLSS concentrations could be retained in the system (up to 38,000mgL−1) with the contribution of UF (ultrafiltration) unit. During the filtration of activated sludge, the fluxes decreased with increasing MLSS. Cake formation fouling was determined as dominant fouling mechanisms. The results demonstrate that jet loop membrane bioreactor system was a suitable and effective treatment choice for treating dairy industry wastewater. [Copyright &y& Elsevier]

The creation of a biofilm as a specialized biosystem, its development, and activity were studied at 3 critical control points of biofilter operation: start-up, transition from batch to sequencing batch regimen, and set-up of stable sequencing batch process. Five variants of biosystems were investigated with an inoculum from specially adapted real activated sludge, enriched with various combinations of 3 microbial preparations. A stable and working biofilm was developed in the phase of stabilized sequencing batch process. The differences among biodegradation effectiveness of the 5 variants were insignificant during that phase and the effect of the preparations was low. The effectiveness of organic removal for the 5 bioaugmentation approaches reached 60% for protein, 70% for chemical oxygen demand, and 97% for lactose. Commercial inocula did not improve final reactor performance over an inoculum from a municipal wastewater treatment plant alone. [ABSTRACT FROM AUTHOR]

Wastewater obtained from a local dairy industry was simultaneously utilized and treated for the production of sophorolipids (SLs), a glycolipids type of biosurfactant, by the yeast Candida bombicola. The dairy wastewater, after initial characterization, was utilized as media with or without adding extra carbon and nitrogen source in the study. A maximum yield of 62 g/l of SLs was found when the yeast was grown on the dairy wastewater supplemented with glucose (10% w/v), yeast extract (0.2% w/v), and soybean oil (10% v/v) in batch shake flasks. Chemical oxygen demand (COD) analysis of the wastewater during the yeast fermentation revealed more than 80% COD removal efficiency in all the experiments. High yield of SLs together with high COD removal efficiency of the yeast in the present study revealed good potential of the system in pretreating such wastewaters and for the production of valuable bioproducts. In addition, the critical micelle concentration and minimum surface tension against water using the produced SLs were found to be 30 mg/l and 33.6 mN/m, respectively. Further, its stability over a wide range of pH (2-10), temperature (up to 120 min of boiling) and salt concentrations (20% NaCl) confirmed the potential of the produced SLs in environmental applications. [ABSTRACT FROM AUTHOR]

Abstract: Present study reports treatment of simulated dairy wastewater (SDW) by inorganic coagulants such as poly aluminum chloride (PAC), ferrous sulphate (FeSO4) and potash alum (KAl(SO4)2·12H2O). Batch coagulation experiments were conducted to evaluate the influence of initial pH (pHi : 5–10) and coagulant dosage (m: 100–5000 mg/L) on chemical oxygen demand (COD) removal from SDW. Residual COD and system pH were observed as function of time. Optimum pHi (pHi,op ) was found to be 8.0 for all the three coagulants. Optimum m (mop ) was found to be 300, 800 and 500 mg/L for PAC, FeSO4 and KAl(SO4)2·12H2O, respectively, giving 69.2, 66.5 and 63.8% COD removal efficiency in 30 min. Heating values of the sludge generated by the coagulants PAC, FeSO4 and KAl(SO4)2·12H2O were found to be 20.7, 29.6 and 17.3 MJ/kg, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Dairy wastewater was applied as the source of organic carbon in photobiological generation of hydrogen in the presence of Rhodobacter sphaeroides O.U. 001. Experiments were performed as batch tests with concentration of the waste varying from 5 to 40 v/v %, and concentration of inoculum of 0.36 g dry wt/l under illumination of 9 klx. The highest volumes of photogenerated hydrogen were obtained at concentration of 40 v/v %, but the maximal substrate yield was reached for lower concentrations of the waste (5–10 v/v %). Changes in concentrations of substrates and products were used for determination of kinetic model. An application of constant pH close to 7 allows for use the non-treated waste in photobiological hydrogen generation with good yield. [ABSTRACT FROM AUTHOR]

Abstract: Present study reports treatment of synthetic dairy wastewater (SDW) in terms of chemical oxygen demand (COD) removal by means of adsorption onto activated carbon-commercial grade (ACC) and bagasse fly ash (BFA). Optimum conditions for SDW treatment were found to be: initial pH≈4.8, adsorbent dose of 20g/l for ACC and 10g/l for BFA and contact time ≈8h. Pseudo-second-order kinetic model was found to fit the kinetic data and Redlich–Peterson isotherm model was generally found to best represent the equilibrium data for SDW treatment by ACC and BFA. The change in entropy and enthalpy for SDW adsorption onto ACC and BFA were estimated as 125.85kJ/molK and 91.53kJ/mol; and 25.71kJ/molK and 17.26kJ/mol, respectively. The negative values of change in Gibbs free energy indicate the feasibility and spontaneous nature of the adsorptive treatment. [Copyright &y& Elsevier]

The filamentous fungus Rhizopus microsporus CPQBA 312-07 DRM was grown in solid-state cultivation and the fermented solid produced was used to hydrolyze triacylglycerols in a high-fat dairy wastewater. For the solid-state cultivation, a mixture of sunflower seed meal and sugarcane bagasse (1:3 by mass on dry basis) was selected. After 18 h of culture, the fermented product had an activity, measured titrimetrically against triolein, of 26 U per gram of dry solids. This substrate mixture does not suffer from compaction and therefore can be used in large scale solid-state cultivation bioreactors. When used to pretreat a high-fat dairy wastewater, with an oil and grease level above 1300 mg/L, the fermented solid reduced the oil and grease level to below 300 mg/L after 72 h at 35 °C. Further work is required to improve the production of lipolytic activity in the solid-state cultivation step and to find the optimum pretreatment time in the wastewater pretreatment step. [ABSTRACT FROM AUTHOR]

The potential for an ecologically engineered treatment system to improve water quality is supported by the effective treatment of wastewater by existing systems such as Living Machines and treatment wetlands. This article describes these treatment systems and their application for waste treatment and presents preliminary results of a laboratory-scale system to treat dairy wastewater. This study used an ecological treatment system, similar to a Living Machine, consisting of five 230 L tanks, that included an anaerobic tank, two aerobic tanks, a clarifier, an aquaculture tank, and a 115 L wetland mesocosm. The preliminary results demonstrate the potential for this technology to be used in the treatment of dairy wastewater following further research and modifications. Approximately 80% of the solids added were removed in the first three tanks. Reductions in TN and TKN were as great as 90% and 94%, respectively. The reductions in NH4-N were consistently greater than 99%, and as much as 32.3% of the NO3-N was removed. A limited amount of PO4-P was removed by the system, only 28.2% over 168 h of treatment. Qualitative results demonstrated the potential of these systems to utilize waste inputs to produce value-added products. [ABSTRACT FROM AUTHOR]

Abstract: This research was conducted to study the relationships between pH, dissolved oxygen (DO), and oxidation–reduction potential (ORP) during low-intensity aeration of dairy wastewaters and to determine potential strategies for monitoring and/or control of this treatment process. The results of this study ascertained that, close to the detection limit of commercially available DO probes (0.1mg/l), DO is a poor indicator of the oxidation–reduction status of the dairy wastewater during this treatment processes. All the three parameters (ORP, DO, and pH) displayed features defining stabilization of the wastewater and hence all three can be used singly or in combination to monitor and/or to control this treatment process. The study also established strong linear relations between ORP and the log of DO; manifest in the high-correlation coefficients of 0.98 and 0.95 at the aeration rates of 0.067 and 0.034-l[air]l−1 [manure]min−1, respectively. The latter observation confirms the higher sensitivity of ORP over DO at very low-oxygen levels; a fact which indicates the superiority of ORP in the monitoring and control of oxidation–reduction status of the wastewater close to DO detection limit. Finally, both total volatile solids (TVS) and chemical oxygen demand (COD), which are common measures of wastewater stabilization; correlated well with pH, DO, and ORP during the entire treatment process. However, because the measurements of DO are erratic close to the DO detection limit, and because ORP and pH measurements are much more consistent than the DO in the entire range of treatment, these two parameters will be more suitable for monitoring and control especially of extended aeration treatments. [Copyright &y& Elsevier]

Acidogenesis of dairy wastewater produced volatile fatty acids, mainly acetate and propionate, plus hydrogen as by-product. Zinc (Zn) inhibited acidogenesis at concentrations over 10 mg l−1; but at 10 mg l−1, or less, it enhanced acidogenesis slightly. On the other hand, copper (Cu) inhibited acidogenesis at all tested concentrations ranging 5-400 mg l−1. Production of acetate was inhibited by both metals at all concentrations; but production of propionate and hydrogen was favored at low concentrations of Zn (up to 80 mg l−1) and Cu (up to 40 mg l−1). Production of hydrogen corresponded with the degradation of carbohydrate and the production of propionate. Overall, Cu was 1.4-4.3 folds more toxic than Zn, according to the overall production patterns of fatty acids and hydrogen as well as degradation patterns of carbohydrate and protein. [ABSTRACT FROM PUBLISHER]