Water management for Power-to-X offshore platforms: an underestimated item.

Increasing carbon dioxide (CO2) concentration in the atmosphere is considered one of the most important challenges today. Therefore, capturing CO2 and producing alternative energy sources through Power-to-X (PtX) approaches have become relevant scientific topics in recent years. However, there is a significant research gap regarding water management in PtX processes, particularly in offshore operations. The present study evaluates relevant aspects and possible challenges with respect to water management as well as mass and energy balances in conceptual offshore methane and methanol production platforms. The results show that 1600 m3 of seawater must be desalinated to supply the electrolyzer and reach a daily 50-Megagram (Mg) hydrogen production. Around 1100 m3 of brine coming out of the desalination plant may be discharged to the sea as long as prior environmental impact assessments are conducted. Additionally, 273 Mg and 364 Mg CO2 need to be generated daily by direct air capture to produce 99 Mg day-1 methane and 265 Mg day-1 methanol, respectively. The daily produced methane and methanol wastewater is estimated to be 223 and 149 m3, respectively. Based on the scant literature on methanol wastewater, this is expected to contain toxic substances. Zero liquid discharge (ZLD) is proposed as wastewater method. The corresponding energy demand for the water management facilities is projected to be negligible compared to the other PtX processes. The presented management of water streams in PtX platforms would not only help recover some of the resources (water, hydrogen and methanol), but also substantially contribute to the production cycle itself while leading toward a more sustainable approach.

Removal of Diverse and Abundant ARGs by MF-NF Process from Pig Manure and Digestate.

Antimicrobial resistances are emerging as one main threat to worldwide human health and are expected to kill 10 million people by 2050. Intensive livestock husbandry, along with biogas digestate, are considered as one of the biggest ARG reservoirs. Despite major concerns, little information is available on the diversity and abundance of various ARGs in small to large scale pig farms and biogas digestate slurry in Germany, followed by their consequent removal using microfiltration (MF)-nanofiltration (NF) process. Here, we report the identification and quantification of 189 ARGs in raw manure and digestate samples, out of which 66 ARGs were shared among manures and 53 ARGs were shared among both manure and digestate samples. The highest reported total ARG copy numbers in a single manure sampling site was 1.15 × 108 copies/100 µL. In addition, we found the absolute concentrations of 37 ARGs were above 105 copies/100 µL. Filtration results showed that the highly concentrated ARGs (except aminoglycoside resistance ARGs) in feed presented high log retention value (LRV) from 3 to as high as 5 after the MF-NF process. Additionally, LRV below 2 was noticed where the initial absolute ARG concentrations were ≤103 copies/100 µL. Therefore, ARG removal was found to be directly proportional to its initial concentration in the raw manure and in digestate samples. Consequently, some ARGs (tetH, strB) can still be found within the permeate of NF with up to 104 copies/100 µL.

MF-NF Treatment Train for Pig Manure: Nutrient Recovery and Reuse of Product Water.

The livestock industry negatively impacts the environment by producing high organic and mineral loaded manure and wastewater. On the contrary, manure is also considered as the major focal point of resource recovery. The microfiltration (MF) process in manure treatment is well known for being the least complex and highly energy efficient. However, the major fraction of the dissolve nutrients easily bypasses the MF membranes. In this research work, we reported the efficiency of using MF-nanofiltration (NF) treatment train in a dead-end filtration system for the treatment of raw manure. The objectives were to produce nutrient rich separate streams in reduced volumes and a particle and pathogen-free product water. MF removed TSS above 98% and the COD and phosphorus (P) retention were noticed above 60 and 80%, respectively, within a reduced MF concentrate volume, which accounted for 40% of the initial feed volume. The NF of MF permeate by NF270 showed most promising results by concentrating overall 50 and 70% of the total nitrogen (TN) and potassium (K) within a reduced NF concentrate volume, which accounted for 30% of the initial MF feed volume. Finally, the MF-NF treatment train of raw pig manure could produce a particle-free product water that can be reused in farms to wash barns, to irrigate nearby cultures, or can be applied to specific fields based on the demand.